Diabetes

Both types of diabetes can cause serious complications. With regular monitoring and good control of the raised blood sugars these can be significantly reduced. In addition to the treatment from healthcare professionals, it is very important for people with diabetes to understand their condition and be able to manage their diabetes.

Types of diabetes

Diabetes mellitus (just called diabetes from now on) occurs when the level of sugar (glucose) in the blood is higher than normal. There are two main types of diabetes - type 1 diabetes and type 2 diabetes. See the separate leaflet called What's the difference between type 1 and type 2 diabetes?

This leaflet refers to diabetes mellitus (now usually just known as diabetes); there is a separate condition called diabetes insipidus which is always called by its full name.

Type 1 diabetes

Around 10% of people with diabetes have type 1 diabetes. Type 1 diabetes is an autoimmune condition. It is not caused by someone's diet or lifestyle. It usually develops quite quickly, over days or weeks, as the pancreas stops making insulin. It usually (but not always) develops in childhood. See the separate leaflet called Type 1 diabetes.

Type 2 diabetes

Around 90% of people with diabetes have type 2 diabetes. Type 2 diabetes is more common in people who are overweight or obese. It tends to develop gradually (over months or years) because the changes in the body develop quite slowly. Type 2 diabetes can be caused by the pancreas not producing enough insulin, or the body not responding properly to the insulin that is produced - and often both.

Type 2 diabetes usually starts in middle-aged or older adults but is increasingly being seen in children and in young adults. See the separate leaflet called Type 2 diabetes.

Gestational diabetes

As well as type 1 and type 2 diabetes, there are other types of diabetes. Pregnant women who have never had diabetes before but who have high blood glucose levels during pregnancy have gestational diabetes. Gestational diabetes usually goes away after birth, but women who have had gestational diabetes are more likely to develop type 2 diabetes in future. Gestational diabetes affects about 4% of all pregnant women. See the separate leaflet called Diabetes and pregnancy.

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Other types of diabetes

There are also a number of rarer forms of diabetes, including:

• Secondary diabetes: diabetes can be caused by other diseases. Examples include diseases that affect the pancreas such as cystic fibrosis and chronic pancreatitis. Diabetes can also be caused by other hormone (endocrine) diseases, such as Cushing's syndrome and acromegaly.

• Latent autoimmune diabetes of adults (LADA): a slow-onset form of type 1 diabetes that occurs in adults, often with a slower onset than the usual type 1 diabetes that starts in childhood. LADA is sometimes called 'type 1.5 diabetes', because it has similarities to both type 1 and type 2 diabetes and is sometimes thought of as an 'in-between' condition.

• Maturity-onset diabetes of the young (MODY): this includes several forms of diabetes which are caused by genetic defects of the cells in the pancreas that make insulin.

• Wolfram's syndrome: another genetic cause of diabetes. It is also called DIDMOAD (because it causes diabetes insipidus, diabetes mellitus, optic atrophy and deafness).

• Other genetic diseases that can cause diabetes: these include Friedreich's ataxia and haemochromatosis.

What causes diabetes?

Diabetes is a condition where there is not enough insulin being produced by the pancreas. Insulin is a hormone that the body needs in order to move glucose into cells to be used for energy. Insulin also helps the liver to store blood sugar to be used later. So, if insulin levels are too low, blood sugar (glucose) levels increase.

Type 1 diabetes and type 2 diabetes have different causes.

Causes of type 1 diabetes

Type 1 diabetes is thought to be an auto-immune condition where the body's immune system attacks and destroys the cells in the pancreas which produce insulin. There is a genetic component to type 1 diabetes (it is more common in children who have a relative with type 1 diabetes) but there is probably an environmental factor too - in some people, an event probably "triggers" the start of the diabetes. For example there was a significant increase in diagnoses of type 1 diabetes after COVID infections, even where the child had very few symptoms from COVID.

Type 1 diabetes is not caused by any type of diet or lifestyle. We don't yet know of any way to prevent type 1 diabetes from developing.

Causes of type 2 diabetes

Type 2 diabetes can be caused by insulin not working properly (insulin resistance), or by the pancreas not producing enough insulin. Often, insulin resistance develops first, so the pancreas has to produce more and more insulin, and eventually struggles to be able to produce enough insulin for the body's needs.

Type 2 diabetes has a number of possible causes, including:

• Being overweight or having obesity. This is the most common cause of type 2 diabetes.

  • Having excess fat stored internally around the liver and pancreas is also linked to developing type 2 diabetes, and can happen in people who are a healthy weight.

• Genetics. Having a family history of type 2 diabetes increases the risk of developing it.

• Diet. Type 2 diabetes is not directly caused by eating certain foods, but a diet with lots of high-calorie foods can lead to overweight and obesity, which can then lead to type 2 diabetes. A diet that is high in the following foods increases the risk of developing type 2 diabetes:

  • High-sugar food and drinks, especially drinks containing added sugar, such as fizzy drinks or soda.

  • Red meat and processed meat.

  • Refined carbohydrates, such as white rice and white bread.

  • Ultra-processed foods.

• Not getting enough physical activity. This makes it harder for the body to manage blood sugar levels.

• Ethnicity. People from certain ethnic backgrounds are more likely to get type 2 diabetes, including people from South Asian, Black Caribbean, and Black African backgrounds.

Lifestyle changes can prevent or delay the onset of type 2 diabetes.

What are the symptoms of diabetes?

The first symptoms of diabetes may include:

• Being very thirsty a lot of the time.

• Passing a lot of urine. (This is because blood sugar (glucose) leaks into the urine which then pulls out extra water through the kidneys.)

• Tiredness, weight loss and feeling generally unwell.

In people with type 1 diabetes, the symptoms tend to develop quickly, over a few days or weeks. Untreated type 1 diabetes causes people to become very unwell. Some people, especially children, with type 1 diabetes develop the disease too quickly to spot some of these symptoms.

Once diabetes treatment is started, symptoms of diabetes should go away. However, the symptoms may come back if blood glucose levels become high again.

Type 2 diabetes symptoms

Type 2 diabetes develops much more slowly than type 1 diabetes. Symptoms may not start until someone has had type 2 diabetes for a number of years. Many people with type 2 diabetes do not have any symptoms at all. This means that people with type 2 diabetes may already have complications of diabetes (see below) when diabetes is first diagnosed. Even though the symptoms of type 2 diabetes are often less severe, the condition is still very important to manage well.

How is diabetes diagnosed?

There are several ways of diagnosing diabetes. These include:

• A blood test to look at the level of glucose in the blood.

• A different blood test for glycosylated haemoglobin (haemoglobin A1c, or HbA1c). HbA1c measures the average level of blood sugar over the last 3 months.

  • This is very commonly used to diagnose and monitor type 2 diabetes.

  • It is not suitable for the diagnosis of type 1 diabetes, but is used to monitor the control of type 1 diabetes.

• An oral glucose tolerance test (OGTT), where blood glucose levels are measured before and after taking a sugary drink.

  • This is the main test for gestational diabetes.

Read more in the separate leaflet called Tests for blood sugar (glucose) and HbA1c.

How is diabetes treated?

Healthy lifestyle and diet

People with diabetes should follow a healthy lifestyle with a healthy diet, maintaining an ideal body weight, taking regular exercise and not smoking.

People with type 2 diabetes can sometimes be managed by lifestyle changes alone. By losing weight and following a low-carbohydrate diet (or, with close medical supervision, a very low-calorie diet), many people can bring their blood sugar back to normal without medication.

Insulin treatment

People with type 1 diabetes always need treatment with insulin, and cannot live without it. Insulin is life-saving for people with type 1 diabetes.

Insulin is sometimes used by people with type 2 diabetes, but usually only if other medications haven't worked. See the separate leaflet called Insulins.

Medicines for type 2 diabetes

Many people with type 2 diabetes take one or more medicines if a healthy lifestyle is not enough to control blood sugar (glucose) levels.

These include tablets and injections. See the separate leaflet called Type 2 diabetes treatment for more detail.

Monitoring blood pressure and cholesterol levels

Treating diabetes is not just about managing blood glucose levels (although this is important). It is also essential to reduce the risk of the complications of diabetes (see below). It is therefore important to keep blood pressure and cholesterol levels in the normal range. Read more in the separate leaflet called Diabetes and high blood pressure.

The treatment for diabetes includes regular monitoring to diagnose and treat complications at an early stage.

When people with diabetes are unwell for any reason, even just a simple viral infection, their blood glucose control can be affected. It is therefore very important to know what to do during an illness. Read about advice for people with diabetes when unwell, in the separate leaflet called Diabetes and Illness.

Aims of diabetes treatment

Diabetes cannot usually be cured but it can be treated successfully. If a high blood glucose level is brought down to a normal or near-normal level, symptoms will ease. For many people, type 2 diabetes can be reversed (and may be considered "cured") with weight loss and exercise but will come back if weight is gained.

Complications of diabetes are a risk even without any symptoms of diabetes. Studies have shown that people who have better glucose control have fewer complications (such as heart disease or eye problems) compared with those people who have poorer control of their glucose level.

Therefore, the main aims of treatment are:

• To keep blood glucose level as near normal as possible.

• To reduce any other risk factors that may increase the risk of developing complications. In particular, to stop smoking, lose weight or lower your blood pressure if needed and to keep blood lipids (cholesterol and triglyceride) low.

• To detect any complications as early as possible. Treatment can prevent or delay some complications from becoming worse.

Healthy diet and other lifestyle advice

It is important to eat a healthy diet. This diet is the same as that recommended for everyone. It is not the case that particular special foods are needed for people with diabetes. 'Diabetic foods' still raise blood glucose levels, may contain just as much fat and calories and are usually more expensive than non-diabetic foods.

Other diet and lifestyle advice includes:

• Eating a diet low in fat, salt and sugar and high in fibre, with plenty of fruit and vegetables.

• Knowing how to balance the right amount of insulin for the amount of food that you eat. See the separate leaflet called Type 2 Diabetes Diet.

• Stopping smoking. If necessary, nicotine replacement therapy (nicotine gum, etc) may help to stop smoking.

• Regular physical activity. This also reduces the risk of some complications such as heart and blood vessel disease. A minimum of 30 minutes' brisk walking at least five times a week is advised for those who are able.

• Taking part in vigorous exercises- for example, swimming, cycling, jogging, dancing.

• Depending on age, it may be advised to take a medicine to lower the cholesterol level. This will help to lower the risk of developing some complications such as heart disease and stroke.

• It is best to try to lose weight if overweight or obese. Excess weight is also a risk factor for heart and blood vessel disease. Getting to a perfect weight may be difficult but losing some weight will always help.

There is no need to give up alcohol completely unless wanting to. Whether people have diabetes or not, healthy guidelines in the UK generally recommend a limit of 14 units a week for both men and women (government guidelines have recently been revised for men). See the separate leaflet called Alcohol and Sensible Drinking. However, drinking alcohol when you have diabetes can make an episode of hypoglycaemia (a 'hypo') more likely.

Immunisation

People with diabetes should be immunised against flu (each autumn), COVID (whenever this is offered) and immunised against infection from pneumococcal germs (bacteria). These infections can be particularly dangerous for people with diabetes.

Monitoring blood glucose levels

Anyone with diabetes who needs treatment with insulin should monitor their blood glucose levels. This is usually not necessary for people with type 2 diabetes who do not need insulin.

It is important to have regular checks as some complications, particularly if detected early, can be treated or prevented from becoming worse.

Doctors, nurses, dieticians, specialists in foot care (podiatrists), specialists in eye health (optometrists) and other healthcare workers all play a role in giving advice and checking on progress. As well as ongoing advice on diet and lifestyle, regular checks may include:

Checking levels of blood glucose, HbA1c, cholesterol and blood pressure

It is important to keep blood glucose, cholesterol and blood pressure levels as normal as possible. The HbA1c blood test helps to check blood glucose control. Ideally, the aim is to keep HbA1c less than 48 mmol/mol. However, this may not always be possible to achieve and the target level of HbA1c should be agreed with your doctor. For people with type 2 diabetes the aim is often to keep the HbA1c to less than 59 mmol/mol.

Checking for early signs of complications

• Eye checks - to detect problems with the back of the eye, the retina (a possible complication of diabetes) which can often be prevented from getting worse. Increased pressure in the eye (glaucoma) is also more common in people with diabetes and can usually be treated. Read more in the separate leaflet Diabetic retinopathy.

• Blood tests - these include checks on kidney function, and other general tests.

• Urine tests - these include testing for protein in the urine, which may indicate early kidney problems. Read more in the separate leaflet Diabetic kidney disease.

• Foot checks - to help to prevent foot ulcers. Read more in the separate leaflet Diabetic Foot Ulcers.

• Tests for the sensation in legs to detect early nerve damage. See the separate leaflets called Diabetic neuropathy and Diabetic amyotrophy.

Complications of diabetes

Dehydration

If blood sugar (glucose) levels are not well controlled this may cause a lack of fluid in the body (dehydration), tiredness and drowsiness. This may progress to a serious illness which can be life-threatening, especially if you have type 1 diabetes.

Infections

A very high blood glucose level sometimes develops as a result of other illnesses such as any infections. People with diabetes who use insulin injections may need to adjust the dose of insulin to keep the blood glucose levels normal.

Ketoacidosis

For people with type 1 diabetes, high blood glucose levels can lead to acids called ketones in the bloodstream (this is called ketoacidosis). Less commonly, people with type 2 diabetes may develop a condition with very high blood glucose levels but no ketones (called hyperosmolar hyperglycaemic coma).

Either of these conditions can dangerously reduce the fluid in your body and both conditions need emergency treatment, as they can be fatal.

Hypoglycaemia

Too much insulin (or too high a dose of some of the diabetes tablets) can make the blood glucose level go too low (hypoglycaemia, sometimes called a 'hypo'). This can cause sweating, confusion or a feeling of being generally unwell; occasionally it can cause coma.

Emergency treatment of hypoglycaemia is with sugar, sweet drinks, or a glucagon injection (a hormone which has the opposite effect to insulin) followed by a starchy snack such as a sandwich. See the separate leaflet called Hypoglycaemia (Low blood sugar).

Other complications

Diabetes can cause other problems such as:

• Infections may take longer to get better or be harder to treat, particularly if blood glucose levels are poorly controlled.

• Psychological difficulties such as depression, anxiety and eating disorders.

Routine surgical procedures (such as a joint replacement or hernia repair) will not usually be performed if diabetes control is poor. They will usually be delayed until the Hba1c is at least below 69 mmol/mol.

Long-term complications

If the blood glucose level is higher than normal, over a long period of time, it can have a damaging effect on the blood vessels.

Even a mildly raised glucose level which does not cause any symptoms in the short term can affect the blood vessels in the long term. This may lead to some of the following complications:

• Furring or 'hardening' of the arteries (atheroma) which can cause problems such as angina, heart attacks, stroke and poor circulation.

• Eye problems which can affect vision. This is due to damage to the small arteries of the retina at the back of the eye.

• Kidney damage which sometimes develops into kidney failure.

• Nerve damage.

• Foot problems. These are due to poor circulation and nerve damage.

• Male sexual difficulties (such as erectile dysfunction) and female sexual difficulties (such as a dry vagina, yeast infections and loss of sensation) are common.

The type and severity of long-term complications vary from case to case. In general, the nearer the blood glucose level is to normal, the lower the risk of developing complications. The risk of developing complications is also reduced if other risk factors (such as high blood pressure) are managed fully.

Diabetes burnout

Caring for diabetes is extremely demanding. Diabetes burnout occurs when people feel overwhelmed by their diabetes. This can lead to feeling angry, frustrated, defeated and also worried about not taking care of diabetes well enough.

Burnout can respond well to talking therapies such as cognitive behavioural therapy (CBT). There is also good support from diabetes support groups.

Diabetes in pregnancy

Diabetes in pregnancy is associated with possible complications for the mother and baby. Women with diabetes who become pregnant need very close monitoring and specialist treatment to make sure that the mother and baby remain well with no problems. See the separate leaflet called Diabetes and pregnancy.

Some women develop diabetes in pregnancy, known as gestational diabetes. This usually resolves after the baby has been born. These women are at higher risk of developing type 2 diabetes later on and should have blood tests every year to monitor this.

Can diabetes be prevented?

There is currently no known way to prevent type 1 diabetes although many studies are looking into a number of different possibilities.

Type 2 diabetes can be prevented by following a healthy lifestyle, such as a healthy diet, regular exercise and not being overweight. This is very important for everyone. However, it is particularly important for people who are at increased risk, including those who have pre-diabetes (impaired glucose tolerance) or who have had gestational diabetes or who have a family history of type 2 diabetes.

What is the outlook for people with diabetes?

Although diabetes is associated with serious complications, these complications can be prevented or greatly reduced in severity. A healthy lifestyle, regular monitoring and taking medicines to keep the blood sugar (glucose), blood pressure and cholesterol levels as normal as possible are all very important.

Some people with type 2 diabetes are able to achieve 'diabetes in remission'. This means their blood glucose stays within normal levels without medication. The most successful way to achieve this is with lifestyle changes, including losing weight and either a medically supervised very low-calorie diet or a low-carbohydrate diet.

Understanding glucose and insulin

After eating, various foods are broken down in the gut (intestine) into sugars. The main sugar, glucose, passes through the gut wall into your bloodstream. . Other starchy carbohydrate foods such as potato, rice or breakfast cereals digest down into significant amounts of glucose too.

To remain healthy, your blood sugar (glucose) level should not go too high. So when blood glucose level begins to rise - particularly after eating - the level of a hormone called insulin should also rise.

Insulin works on the cells of the body and makes them take in glucose from the bloodstream, thus lowering the blood glucose again. Some of the glucose is used by the cells for energy. Any glucose not used up in this way is converted into glycogen in the liver or fat in the liver or abdomen.

When the blood glucose level begins to fall (between meals or when there is no food), the level of insulin falls. Some glycogen or fat is then converted back into glucose. This is released from the cells into the bloodstream to keep the blood glucose level normal.

Over time, if there is more glucose in the system than needed for energy, this can lead to central obesity (weight carried around the abdomen) and fatty liver.

Insulin is a hormone that is made by cells called beta cells. These are part of little islands of cells (islets) within the pancreas gland. Hormones are chemicals that are released by glands into the bloodstream and work on various parts of the body.

Diabetes develops if the pancreas is not making enough insulin or if the insulin that you is made does not work properly on the body's cells:

• In type 1 diabetes, the body does not make any insulin at all.

• In type 2 diabetes, levels of insulin may be normal but the body doesn't respond properly to them. This is called insulin resistance. Over time, the body's ability to produce insulin also drops in type 2 diabetes and the blood sugar (glucose) levels therefore remain high.