Health A to Z
Diabetes is a lifelong condition that causes a person's blood sugar level to become too high.
The hormone insulin – produced by the pancreas – is responsible for controlling the amount of glucose in the blood
There are two main types of diabetes:
These pages are about type 2 diabetes. Read more about type 1 diabetes.
Another type of diabetes, known as gestational diabetes, occurs in some pregnant women and tends to disappear after birth.
The symptoms of diabetes occur because the lack of insulin means glucose stays in the blood and isn't used as fuel for energy.
Your body tries to reduce blood glucose levels by getting rid of the excess glucose in your urine.
Typical symptoms include:
Read more about the symptoms of type 2 diabetes.
See your GP if you think you may have diabetes. It's very important for it to be diagnosed as soon as possible as it will get progressively worse if left untreated.
Read about how type 2 diabetes is diagnosed.
Type 2 diabetes occurs when the body doesn't produce enough insulin to function properly, or the body's cells don't react to insulin. This means glucose stays in the blood and isn't used as fuel for energy.
Type 2 diabetes is often associated with obesity and tends to be diagnosed in older people. It's far more common than type 1 diabetes.
Read about the causes and risk factors for type 2 diabetes.
As type 2 diabetes usually gets worse, you may eventually need medication – usually tablets – to keep your blood glucose at normal levels.
Read more about the treatment of type 2 diabetes.
Diabetes can cause serious long-term health problems. It's the most common cause of vision loss and blindness in people of working age.
Everyone with diabetes aged 12 or over should be invited to have their eyes screened once a year for diabetic retinopathy.
Diabetes is also responsible for most cases of kidney failure and lower limb amputation, other than accidents.
Read more about the complications of type 2 diabetes.
If you're at risk of type 2 diabetes, you may be able to prevent it developing by making lifestyle changes.
If you already have type 2 diabetes, it may be possible to control your symptoms by making the above changes. This also minimises your risk of developing complications.
Read more about living with type 2 diabetes.
The symptoms of diabetes include feeling very thirsty, passing more urine than usual, and feeling tired all the time.
The symptoms occur because some or all of the glucose stays in your blood and isn't used as fuel for energy. Your body tries to get rid of the excess glucose in your urine.
The main symptoms, which are common to both type 1 diabetes and type 2 diabetes, are:
The signs and symptoms of type 1 diabetes are usually obvious and develop very quickly, often over a few weeks.
These signs and symptoms aren't always as obvious, however, and it's often diagnosed during a routine check-up.
This is because they are often mild and develop gradually over a number of years. This means you may have type 2 diabetes for many years without realising it.
See your GP as soon as possible if you think you may have diabetes. Early diagnosis and treatment for type 2 diabetes is very important as it may reduce your risk of developing complications later on.
Type 2 diabetes occurs when the pancreas, a large gland behind the stomach, can't produce enough insulin to control your blood glucose level, or when the cells in your body don't respond properly to the insulin that is produced.
This means your blood glucose levels may become very high, and is known as hyperglycaemia.
Hyperglycaemia can occur for several reasons, including:
Hyperglycaemia causes the main symptoms of diabetes, which include extreme thirst and frequent urination.
Type 2 diabetes occurs when the pancreas doesn't produce enough insulin to maintain a normal blood glucose level, or the body is unable to use the insulin that is produced (insulin resistance).
The pancreas is a large gland behind the stomach that produces the hormone insulin. Insulin moves glucose from your blood into your cells, where it's converted into energy.
In type 2 diabetes, there are several reasons why the pancreas doesn't produce enough insulin.
Three of the main risk factors for developing type 2 diabetes are:
People of south Asian and African-Caribbean origin also have an increased risk of developing complications of diabetes, such as heart disease, at a younger age than the rest of the population.
These risk factors are discussed in more detail below.
Read about reducing your risk of type 2 diabetes.
Your risk of developing type 2 diabetes increases with age. This may be because people tend to gain weight and exercise less as they get older.
White people over the age of 40 have an increased risk of developing the condition. People of south Asian, Chinese, African-Caribbean and black African origin have an increased risk of developing type 2 diabetes at a much earlier age.
However, despite increasing age being a risk factor for type 2 diabetes, over recent years younger people from all ethnic groups have been developing the condition.
It's also becoming more common for children – as young as seven in some cases – to develop type 2 diabetes.
Genetics is one of the main risk factors for type 2 diabetes. Your risk of developing the condition is increased if you have a close relative such as a parent, brother or sister who has the condition.
The closer the relative, the greater the risk. A child who has a parent with type 2 diabetes has about a one in three chance of also developing the condition.
You're more likely to develop type 2 diabetes if you're overweight or obese.
For most people in the UK, a body mass index (BMI) of:
However, some groups have a higher risk of developing type 2 diabetes:
Fat around your tummy (abdomen) particularly increases your risk. This is because it releases chemicals that can upset the body's cardiovascular and metabolic systems.
This increases your risk of developing a number of serious conditions, including:
Measuring your waist is a quick way of assessing your diabetes risk. This is a measure of abdominal obesity, which is a particularly high-risk form of obesity.
Some groups have a higher risk of developing type 2 diabetes, based on their waist measurements:
Use the BMI calculator to find out if you're a healthy weight for your height.
Exercising regularly and reducing your body weight by about 5% could reduce your risk of getting diabetes by more than 50%.
Read information and advice about losing weight.
Your risk of developing type 2 diabetes is also increased if your blood glucose level is higher than normal, but not yet high enough to be diagnosed with diabetes.
This is sometimes called pre-diabetes, and doctors sometimes call it impaired fasting glycaemia (IFG) or impaired glucose tolerance (IGT).
Pre-diabetes can progress to type 2 diabetes if you don't take preventative steps, such as making lifestyle changes. These include eating healthily, losing weight if you're overweight, and taking plenty of regular exercise.
Women who have had gestational diabetes during pregnancy also have a greater risk of developing diabetes in later life.
It's important for diabetes to be diagnosed early so treatment can be started as soon as possible.
If you experience the symptoms of diabetes, visit your GP as soon as possible. They'll ask about your symptoms and may request blood and urine tests.
Your urine sample will be tested for glucose. Urine doesn't normally contain glucose, but glucose can overflow through the kidneys and into your urine if you have diabetes.
If your urine contains glucose, a specialised blood test known as glycated haemoglobin (HbA1c) can be used to determine whether you have diabetes.
In people who have been diagnosed with diabetes, the glycated haemoglobin (HbA1c) test is often used to show how well their diabetes is being controlled.
The HbA1c test gives your average blood glucose levels over the previous two to three months. The results can indicate whether the measures you're taking to control your diabetes are working.
If you've been diagnosed with diabetes, it's recommended you have your HbA1c measured at least twice a year.
However, you may need to have your HbA1c measured more frequently if:
Unlike other tests, such as the glucose tolerance test (GTT), the HbA1c test can be carried out at any time of day and doesn't require any special preparation, such as fasting. However, the test can't be used in certain situations, such as during pregnancy.
The advantages associated with the HbA1c test make it the preferred method of assessing how well blood glucose levels are being controlled in a person with diabetes.
HbA1c can also be used as a diagnostic test for diabetes and as a screening test for people at high risk of diabetes.
In 2011 the World Health Organization (WHO) recommended that HbA1c could also be used to help diagnose type 2 diabetes in people who aren't known to have the condition.
An HbA1c level of 6.5% (48mmol/mol) or above indicates type 2 diabetes.
Although there's no fixed point to indicate when someone has pre-diabetes, a UK expert group has recommended that an HbA1c level of 6-6.4% (42-47 mmol/mol) would indicate that a person has a high risk of developing diabetes.
A glucose tolerance test (GTT), sometimes known as an oral glucose tolerance test (OGTT), can show if your body is having problems processing glucose.
Before having the test, you'll be asked not to eat or drink certain fluids for 8-12 hours. You may also need to avoid taking certain medications before the test, as they may affect the results.
A blood sample will be taken before the test and your blood glucose will be measured. You'll then be given a sweet glucose drink.
After drinking the glucose drink, your blood glucose will be measured again after two hours. As you will have a long time to wait between blood tests, you may want to take something to read or listen to.
The results of the GTT will show whether you have impaired glucose tolerance (IGT) or diabetes. This will be based on the amount of glucose in your blood both before and after drinking the glucose drink.
Blood glucose is measured in millimoles per litre, often written as mmol/l.
For someone without diabetes, the amount of glucose in their blood should be:
If you have IGT, the amount of glucose in your blood will be:
If you have diabetes, the amount of glucose in your blood will be:
If your test results indicate you have IGT, you may be advised to make lifestyle changes, such as eating more healthily and taking more exercise. Medication to lower your blood glucose level may also be recommended.
If your results indicate you have diabetes, it is likely medication will be prescribed. This will lower your blood glucose level and help keep it under control.
Read more about treating type 2 diabetes.
Increasing the amount of fibre in your diet and reducing your sugar and fat intake, particularly saturated fat, can help prevent type 2 diabetes, as well as manage the condition if you already have it.
Losing 5-10% of your overall body weight over the course of a year is a realistic initial target.
You should aim to continue to lose weight until you've achieved and maintained a BMI within the healthy range, which is:
If you have a BMI of 30kg/m² or more (27.5kg/m² or more for people of south Asian or Chinese origin), you need a structured weight loss programme, which should form part of an intensive lifestyle change programme.
To help you achieve changes in your behaviour, you may be referred to a dietititian or a similar healthcare professional for a personal assessment and tailored advice about diet and physical activity.
Being physically active is very important in preventing or managing type 2 diabetes.
For adults who are 19-64 years of age, the government recommends a minimum of:
An alternative recommendation is to do a minimum of:
Read more about the physical activity guidelines for adults.
In cases where the above activity levels are unrealistic, even small increases in physical activity will be beneficial to your health and act as a basis for future improvements.
Reduce the amount of time spent watching television or sitting in front of a computer. Going for a daily walk – for example, during your lunch break – is a good way of introducing regular physical activity into your schedule.
If you're overweight or obese, you may need to be more physically active to help you lose weight and maintain weight loss.
Your GP, diabetes care team or dietitian can give you more information and advice about losing weight and becoming more physically active.
Type 2 diabetes usually gets worse over time. Making lifestyle changes, such as adjusting your diet and taking more exercise, may help you control your blood glucose levels at first, but may not be enough in the long term.
You may eventually need to take medication to help control your blood glucose levels.
Initially, this will usually be in the form of tablets and can sometimes be a combination of more than one type of tablet. It may also include insulin or another medication that you inject.
Metformin is usually the first medicine used to treat type 2 diabetes. It works by reducing the amount of glucose your liver releases into your bloodstream. It also makes your body's cells more responsive to insulin.
Metformin is recommended for adults with a high risk of developing type 2 diabetes and whose blood glucose is still progressing towards type 2 diabetes, despite making necessary lifestyle changes.
If you're overweight, it's also likely you'll be prescribed metformin. Unlike some other medicines used to treat type 2 diabetes, metformin shouldn't cause additional weight gain.
However, it can sometimes cause mild side effects, such as nausea and diarrhoea, and you may not be able to take it if you have kidney damage.
Sulphonylureas increase the amount of insulin that's produced by your pancreas.
You may be prescribed one of these medicines if you can't take metformin or if you aren't overweight.
Alternatively, you may be prescribed sulphonylurea and metformin if metformin doesn't control blood glucose on its own.
Sulphonylureas can increase the risk of hypoglycaemia (low blood sugar) because they increase the amount of insulin in your body. They can also sometimes cause side effects, including weight gain, nausea and diarrhoea.
Pioglitazone is a type of thiazolidinedione medicine (TZD), which make your body's cells more sensitive to insulin so more glucose is taken from your blood.
It's usually used in combination with metformin or sulphonylureas, or both. It may cause weight gain and ankle swelling (oedema).
You shouldn't take pioglitazone if you have heart failure or a high risk of bone fracture.
Gliptins work by preventing the breakdown of a naturally occurring hormone called GLP-1.
GLP-1 helps the body produce insulin in response to high blood glucose levels, but is rapidly broken down.
By preventing this breakdown, the gliptins (linagliptin, saxagliptin, sitagliptin and vildagliptin) prevent high blood glucose levels, but don't result in episodes of hypoglycaemia.
You may be prescribed a gliptin if you're unable to take sulphonylureas or glitazones, or in combination with them. They're not associated with weight gain.
SGLT2 inhibitors work by increasing the amount of glucose excreted in urine. They may be considered to treat type 2 diabetes if metformin and DPP-4 inhibitors aren't suitable.
The three SGLT2 inhibitors that may be prescribed include:
Each medication is taken as a tablet once a day. The main side effect is a higher risk of genital and urinary tract infections.
Read more about these three new treatment options for type 2 diabetes on the National Institute for Health and Care Excellence (NICE) website.
GLP-1 agonists acts in a similar way to the natural hormone GLP-1 (see the section on gliptins, above).
They're given by injection and boost insulin production when there are high blood glucose levels, reducing blood glucose without the risk of hypoglycaemia episodes ("hypos").
Acarbose helps prevent your blood glucose level increasing too much after you eat a meal. It slows down the rate at which your digestive system breaks carbohydrates down into glucose.
Acarbose isn't often used to treat type 2 diabetes because it usually causes side effects, such as bloating and diarrhoea.
However, it may be prescribed if you can't take other types of medicine for type 2 diabetes.
Nateglinide and repaglinide stimulate the release of insulin by your pancreas. They're not commonly used, but may be an option if you have meals at irregular times.
This is because their effects don't last very long, but they're effective when taken just before you eat.
Nateglinide and repaglinide can cause side effects, such as weight gain and hypoglycaemia (low blood sugar).
If glucose-lowering tablets aren't effective in controlling your blood glucose levels, you may need to have insulin treatment.
This can be taken instead of or alongside your tablets, depending on the dose and the way you take it.
Insulin comes in several different preparations, and each works slightly differently.
For example, some last up to a whole day (long-acting), some last up to eight hours (short-acting) and some work quickly but don't last very long (rapid-acting).
Your treatment may include a combination of these different insulin preparations.
Insulin must be injected because it would be broken down in your stomach like food and unable to enter your bloodstream if it were taken as a tablet.
If you need to inject insulin, your diabetes care team will advise you about when you need to do it.
They will show you how to inject it yourself, and will also give you advice about storing your insulin and disposing of your needles properly.
Insulin injections are given using either a syringe or an injection pen, also called an insulin pen (auto-injector). Most people need between two and four injections of insulin a day.
Your GP or diabetes nurse will also teach a relative or a close friend how to inject the insulin properly.
If you have type 2 diabetes that's controlled using insulin or certain types of tablets, you may experience episodes of hypoglycaemia.
Hypoglycaemia is where your blood glucose levels become very low.
Mild hypoglycaemia (a "hypo") can make you feel shaky, weak and hungry, but it can usually be controlled by eating or drinking something sugary.
If you have a hypo, you should initially have a form of carbohydrate that will act quickly, such as a sugary drink or glucose tablets.
This should be followed by a longer-acting carbohydrate, such as a cereal bar, sandwich or piece of fruit.
In most cases, these measures will be enough to raise your blood glucose level to normal, although it may take a few hours.
If you develop severe hypoglycaemia, you may become drowsy and confused, and you may even lose consciousness.
If this occurs, you may need to have an injection of glucagon into your muscle or glucose into a vein. Glucagon is a hormone that quickly increases your blood glucose levels.
Your diabetes care team can advise you on how to avoid a hypo and what to do if you have one.
To reduce your risk of developing other serious health conditions, you may be advised to take other medicines, including:
Diabetic kidney disease is identified by the presence of small amounts of albumin (a protein) in your urine. If treated early enough, it may be reversible.
If you have type 2 diabetes, your GP or diabetes care team will need to take a reading of your blood glucose level about every two to six months.
This will show how stable your glucose levels have been in the recent past and how well your treatment plan is working.
The HbA1c test is used to measure blood glucose levels over the previous two to three months.
HbA1c is a form of haemoglobin, the chemical that carries oxygen in red blood cells, which also has glucose attached to it.
A high HbA1c level means that your blood glucose level has been consistently high over recent weeks, and your diabetes treatment plan may need to be changed.
Your diabetes care team can help you set a target HbA1c level to aim for. This will usually be less than 59mmol/mol (7.5%). However, it can be as low as 48mmol/mol (6.5%) for some people.
Read more about the HbA1c test.
If you have type 2 diabetes, as well as having your blood glucose level checked by a healthcare professional every two to six months, you may be advised to monitor your own blood glucose levels at home.
Even if you have a healthy diet and are taking tablets or using insulin therapy, exercise, illness and stress can affect your blood glucose levels.
Other factors that may affect your blood glucose levels include drinking alcohol, taking other medicines and, for women, hormonal changes during the menstrual cycle.
If blood glucose monitoring is recommended, you should be trained in how to use a blood glucose meter and what you should do if the reading is too high or too low.
Blood glucose meters aren't currently available for free on the NHS but, in some cases, blood monitoring strips may be. Ask a member of your diabetes care team if you're unsure.
Diabetes UK also provides further information about the availability of blood glucose test strips (PDF, 195kb).
Regularly monitoring your blood glucose levels will ensure your blood glucose is as normal and stable as possible.
As your blood glucose level is likely to vary throughout the day, you may need to check it several times a day, depending on the treatment you're taking.
In home testing, blood glucose levels are usually measured by how many millimoles of glucose are in a litre of blood.
A millimole is a measurement used to define the concentration of glucose in your blood. The measurement is expressed as millimoles per litre, or mmol/l for short.
A normal blood glucose level is 4-6 mmol/l before meals (preprandial) and less than 10 mmol/l two hours after meals (postprandial), although this can vary from person to person.
Your diabetes care team can discuss your blood glucose level with you in more detail.
If diabetes isn't treated, it can lead to a number of other health problems.
High glucose levels can damage blood vessels, nerves and organs.
Even a mildly raised glucose level that doesn't cause any symptoms can have long-term damaging effects.
Prolonged, poorly controlled blood glucose levels increase the likelihood of atherosclerosis, where the blood vessels become clogged up and narrowed by fatty substances.
This may result in poor blood supply to your heart, causing angina, which is a dull, heavy or tight pain in the chest.
It also increases the chance that a blood vessel in your heart or brain will become blocked, leading to a heart attack or stroke.
High blood glucose levels can damage the tiny blood vessels in your nerves.
This can cause a tingling or burning pain that spreads from your fingers and toes up through your limbs. It can also cause numbness, which can lead to ulceration of the feet.
Damage to the peripheral nervous system, which includes all parts of the nervous system that lie outside the central nervous system, is known as peripheral neuropathy.
Diabetic retinopathy is when the retina, the light-sensitive layer of tissue at the back of the eye, becomes damaged.
Blood vessels in the retina can become blocked or leaky, or can grow haphazardly. This prevents light fully passing through to your retina. If it isn't treated, it can damage your vision.
Annual eye checks are usually organised by a regional photographic unit. If significant damage is detected, you may be referred to a doctor who specialises in treating eye conditions (ophthalmologist).
The better you control your blood glucose levels, the lower your risk of developing serious eye problems.
Diabetic retinopathy can be managed using laser treatment if it's caught early enough. However, this will only preserve the sight you have rather than improve it.
If the small blood vessels of your kidney become blocked and leaky, your kidneys will work less efficiently.
It's usually associated with high blood pressure, and treating this is a key part of management.
Damage to the nerves of the foot can mean small nicks and cuts aren't noticed and this, in combination with poor circulation, can lead to a foot ulcer.
About 1 in 10 people with diabetes get a foot ulcer, which can cause a serious infection.
If you have diabetes, look out for sores and cuts that don't heal, puffiness or swelling, and skin that feels hot to the touch. You should also have your feet examined at least once a year.
If poor circulation or nerve damage is detected, check your feet every day and report any changes to your doctor, nurse or podiatrist.
Read more about foot care and diabetes.
In men with diabetes, particularly those who smoke, nerve and blood vessel damage can lead to erection problems. This can usually be treated with medication.
Women with diabetes may experience:
If you experience a lack of vaginal lubrication or find sex painful, you can use a vaginal lubricant or a water-based gel.
If your blood glucose level isn't carefully controlled during the early stages of pregnancy, there's also an increased risk of the baby developing a birth defect.
Pregnant women with diabetes will usually have their antenatal check-ups in hospital or a diabetic clinic, ideally with a doctor who specialises in pregnancy care (an obstetrician).
This will allow your care team to keep a close eye on your blood glucose levels and control your insulin dosage more easily, as well as monitoring the growth and development of your baby.
The NHS diabetic eye screening programme will arrange for you to have your eyes checked every year.
Everyone who is on a diabetes register will be given the opportunity to have a digital picture taken of the back of their eye. Speak to your GP to register.
Eating a healthy, balanced diet is very important if you have diabetes. However, you don't need to avoid certain food groups altogether.
You can have a varied diet and enjoy a wide range of foods as long as you eat regularly and make healthy choices.
You don't need to completely exclude sugary and high-fat foods from your diet, but they should be limited.
If your diet is well balanced, you should be able to achieve a good level of health and maintain a healthy weight.
As physical activity lowers your blood glucose level, it's very important to exercise regularly if you have diabetes.
However, before starting a new activity, speak to your GP or diabetes care team first.
As exercise will affect your blood glucose level, your care team may have to adjust your insulin treatment or diet to keep your blood glucose level steady.
As well as increasing this risk further, smoking also increases your risk of many other serious smoking-related conditions, such as lung cancer.
If you want to give up smoking, your GP can provide you with advice, support and treatment to help you quit.
If you have diabetes and decide to drink alcohol, avoid drinking more than the recommended daily amounts, and never drink alcohol on an empty stomach.
Depending on the amount you drink, alcohol can cause either high or low blood glucose levels (hyperglycaemia or hypoglycaemia).
Drinking alcohol may also affect your ability to carry out insulin treatment or blood glucose monitoring, so always be careful not to drink too much.
Men and women are advised not to regularly drink more than 14 units a week.
If you have diabetes, you're at greater risk of developing problems with your feet, including foot ulcers and infections from minor cuts and grazes.
This is because diabetes is associated with poor blood circulation in the feet, and blood glucose can damage the nerves.
To prevent problems with your feet, keep your nails short and wash your feet daily using warm water.
Wear shoes that fit properly, and see foot care specialists (a podiatrist or chiropodist) regularly so any problems can be detected early.
Regularly check your feet for cuts, blisters or grazes as you may not be able to feel them if the nerves in your feet are damaged.
See your GP if you have a minor foot injury that doesn't start to heal within a few days.
Read more about feet and diabetes.
If you have type 2 diabetes, you should be invited to have your eyes screened once a year to check for diabetic retinopathy.
Diabetic retinopathy is an eye condition where the small blood vessels in your eye become damaged.
It can occur if your blood glucose level is too high for a long period of time (hyperglycaemia). Left untreated, retinopathy can eventually lead to sight loss.
Read more about diabetic eye screening.
People with diabetes should also see their optician every two years for a regular eye test. Diabetic eye screening is specifically for diabetic retinopathy and can't be relied upon for other conditions.
If you have diabetes and you're thinking about having a baby, it's a good idea to discuss this with your diabetes care team.
Planning your pregnancy means you can ensure your blood glucose levels are as well controlled as they can be before you get pregnant.
You'll need to tightly control your blood glucose level – particularly before becoming pregnant and during the first eight weeks of your baby's development – to reduce the risk of birth defects.
You should also:
Your GP or diabetes care team can give you further advice.
Read more about diabetes and pregnancy.
Many people find it helpful to talk to others in a similar position, and you may find support from a group for people with diabetes.
If you want to get in touch with a trained counsellor directly, you can call the Diabetes UK Helpline on 0345 123 2399 (Monday to Friday, 9am to 7pm) or email email@example.com.
People with diabetes controlled by medication are entitled to free prescriptions and eye examinations.
Some people with diabetes may also be eligible for disability and incapacity benefits, depending on the impact the condition has on their lives.
The main groups likely to qualify for welfare benefits are children, the elderly, and those with learning disabilities, mental health difficulties or diabetes complications.
People over the age of 65 who are severely disabled may qualify for a type of disability benefit called Attendance Allowance.
Carers may also be entitled to some benefits, depending on their involvement in caring for the person with diabetes.
Your local Citizens Advice can check whether you're getting all the benefits you're entitled to. Your diabetes specialist nurse and Citizens Advice can also provide advice about filling in the forms.
If you need to take insulin to control your diabetes, you should have received instructions about looking after yourself when you're ill – known as your "sick day rules".
Contact your diabetes care team or GP for advice if you haven't received these.
The advice you're given will be specific to you, but some general measures that your sick day rules may include could be to:
Seek advice from your diabetes care team or GP if your blood sugar or ketone level remains high after taking insulin, if:
After his victory in the rowing at the 2000 Sydney Olympics, Sir Steve Redgrave became the only British athlete to win five consecutive Olympic gold medals.
But what many people don't realise is that Sir Steve achieved this final triumph against all the odds. Three years before the Sydney Olympics, he discovered he had diabetes.
"It was November 1997 and I had this tremendous thirst coming back from training one day," he says. "After drinking three or four pints of fluids, I knew something wasn't quite right."
Sir Steve's grandfather was also diabetic, so the athlete wasn't totally ignorant of the condition.
While training abroad, he and his team mates were given dipsticks to test their dehydration levels, and Sir Steve could also test his urine for sugar levels.
"For some reason I decided to do my own test, and it came back positive," he says. "I called my wife, who's a doctor, and she suggested going to see my GP.
"My blood sugar level was 32 [the norm is somewhere between 4 and 7], and I was sent to see a specialist. From that day on I've been taking insulin."
The Olympic champion was 35 years old when he was diagnosed with type 2, or adult-onset, diabetes, where the body doesn't make enough insulin or the cells in the body don't use insulin properly. He thought it was the end of his career.
"The little I knew about diabetes was that there were few sportspeople with the condition competing at the level I wanted to be at. I thought it was impossible to be diabetic and do what I did, so obviously I was a little depressed.
"I took it in my stride to some extent, because I'd already achieved four Olympic gold medals.
"But after a consultation, my specialist said he didn't see any reason why I couldn't achieve my dreams in Sydney. He said it wouldn't be straightforward, and he was certainly right about that."
Initially, Sir Steve was put on a low-sugar diet, but he soon found he didn't have the energy to carry out the endurance training needed to compete at the highest level.
His specialist decided that, as he'd performed well on his previous diet of 6,000 calories a day, including a high sugar content, he should go back on that diet and adjust his insulin dose accordingly.
"After I won in Sydney, my specialist and I did a press conference and another diabetes specialist stood up and said, 'You're a very lucky man'," Sir Steve recalls.
"He said if I'd come to the clinics of any of the specialists in that room, they'd have said I couldn't do it. They were amazed."
In theory, he could have been given tablets to control his blood sugar level, but Sir Steve says they wouldn't have given him enough insulin in his system for the amount of training he was doing.
"I was testing my blood sugar levels, using a pin prick to draw a spot of blood, 10 times a day. Normally, people with diabetes do it just once.
"If you're not diabetic, your body naturally adjusts your insulin levels, so I was just trying to mimic as closely as possible what the body does naturally."
Sir Steve now uses an insulin pump. Instead of injecting several times a day, the pump is attached all day, every day, feeding a small amount of the medication into the body all the time.
The pump is about the size of a pack of playing cards and is attached to the side of the abdomen. The infusion unit only needs changing every three days.
"It's a lot more convenient," he says, "particularly when you're out and about. And you can take it off to shower or exercise. The down side is that I sometimes wake up during the night with it wrapped around me.
"There are fundamental changes you have to make when you discover you have diabetes, but there's no reason why you can't achieve your dreams.
"I made the decision that diabetes was going to live with me; I wasn't going to live with diabetes."
Clare Mehmet, a 58-year-old retired telecommunications interpreter, found out by chance that she had type 2 diabetes 10 years ago.
"I was waiting for a train when I saw a poster saying, 'You could have diabetes: Are you thirsty all the time? Are you always tired? Is your vision blurred?'
"I was shocked because I'd been experiencing all the symptoms, but put it to the back of my mind. So I promptly made an appointment with my GP, who confirmed that I had type 2 diabetes.
"At first I was terrified. I always thought people with diabetes were seriously ill, but once I looked into the condition I realised that as long as you change your diet and keep yourself fit and healthy, you can lead a full and active life.
"I've joined lots of support groups since I was diagnosed with diabetes, and I do voluntary work to raise awareness about the condition. It's important that people watch out for the signs.
"Late diagnosis can cause serious complications, such as blindness, kidney failure, heart disease, stroke and nerve damage, which could lead to blood flow problems and even amputation. So if you have any worries, get tested."
Charles Torkington, 54, an IT specialist from Thirsk in North Yorkshire, says being diagnosed with diabetes gave him the determination to change his diet and his life.
"I was a pilot for 30 years, and was fit and active. But when I left the forces eight years ago, my life changed.
"I studied IT and stopped exercising due to work pressures. My weight went up to just over 15 stone (95kg).
"Then I started getting pains in my legs, which I thought were linked to a back injury. My doctor said it was either cancer or diabetes.
"A week later, he rang to say I had diabetes. My blood sugar levels were so high they were off the scale.
"My GP put me on an exercise and diet regime, reducing portion sizes and cutting out alcohol completely. I now eat lots of vegetables, salmon and skinned chicken, and no processed food at all.
"I run up the stairs instead of walking, I walk to get the weekend shopping, and polish the car vigorously by hand. I also walk three or four miles in the countryside at weekends.
"I'm now 11 stone 8lb (74kg) and feel so much better. I've got loads of energy and my blood sugar is under control. Becoming diabetic forced me to change my life. I'm very happy now."
Shafina Bibi was shocked to hear she had diabetes, but now she's changed her lifestyle and has never felt better.
"I was devastated when I found out I had diabetes," says Shafina Bibi, 35. "I never dreamed it would happen to me."
Shafina moved to the UK from Pakistan nearly 15 years ago. As someone of south Asian origin, she had a higher risk of getting diabetes. She was diagnosed with type 2 diabetes in 2001 and feared the worst.
"Being south Asian and overweight, I was more at risk," Shafina says. In fact, the more overweight and unfit you are, the greater your risk of developing the condition. More than 80% of people with type 2 diabetes are overweight.
Shafina also developed temporary gestational diabetes during pregnancy, and this put her at an even greater risk of developing type 2 diabetes.
"But in spite of all these high-risk factors, I never dreamed it would happen to me," Shafina says. "Suddenly, I was told I was at greater risk of serious complications such as heart attacks, blindness and kidney damage. I felt very frightened and alone.
"When the diabetes educator from the community diabetes team called to invite me to their 'new to type 2' group education session, it was a huge relief. The educator held the group at my local community centre and spoke in Urdu, my first language, which put me at ease.
"She explained all about type 2 diabetes, making it absolutely clear that we should keep fit and slim by exercising, cutting back on fat, and eating more fruit and veg. It began to sink in that if I wanted to see my grandchildren, I'd have to lose some weight.
"When you're a mother of five, finding time to look after yourself is hard. After my youngest was born nearly four years ago, I became very overweight and felt far too tired to exercise.
"But I left the session feeling really motivated. I reduced the oil in my cooking, and cut out butter and ghee. I began eating more fruit and veg and moved from full-fat to semi-skimmed milk.
"Now, when I feel peckish, I eat an apple rather than half a packet of biscuits. I walk my children to school every day and make sure I'm going as fast as I can.
"In the last seven months, I've lost nearly four stone (25kg) and my blood sugar levels have come right down. I feel full of energy. My children can't believe how good their mum looks."