Diabetes

Diabetes is a chronic condition in which the level of glucose (sugar) in the blood is too high. It develops when there is a problem with the hormone insulin and the way it works in the body. Diabetes is one of the most common chronic conditions worldwide, and the risk of developing it increases with age. Some populations have much higher rates of type 2 diabetes than others.

How the body uses glucose#

Glucose is the body’s main source of energy. It comes from foods that contain carbohydrates, such as potatoes, bread, pasta, rice, fruit and milk. After food is digested, glucose is released and absorbed into the bloodstream. From there it needs to move into the body’s tissues so that cells can use it for energy, and any excess is stored in the liver or converted to fat and stored in other tissues.

Insulin is a hormone made by the pancreas, a gland that sits just below the stomach. Insulin opens the channels that let glucose move from the blood into the body’s cells, and it also allows glucose to be stored in muscle, the liver and other tissues. This is part of a process known as glucose metabolism.

In diabetes, either the pancreas cannot make insulin (type 1 diabetes), or the cells do not respond to insulin properly (insulin resistance) and the pancreas cannot produce enough for the body’s needs (type 2 diabetes). When insulin cannot do its job, the glucose channels do not open properly, and glucose builds up in the blood instead of moving into cells for energy. These high blood glucose levels cause the health problems linked to diabetes, often called complications.

Symptoms#

Some types of diabetes have no symptoms and can go undiagnosed for a long time. When symptoms do occur, they can include:

• being more thirsty than usual
• passing more urine
• feeling tired and lethargic
• slow-healing wounds
• itching and skin infections, particularly around the genitals
• blurred vision
• nausea and vomiting
• weight loss
• mood swings

Ketoacidosis is a medical emergency#

Most cases of ketoacidosis occur in people with established type 1 diabetes, especially if they have another illness or miss insulin doses, but it can also be the first sign of type 1 diabetes. Symptoms can include loss of appetite, weight loss, vomiting, passing large amounts of urine, altered consciousness and, in severe cases, coma. Seek immediate medical help if these symptoms occur.

Types of diabetes#

The main types are type 1 and type 2. Other forms include gestational diabetes, pre-diabetes and diabetes insipidus.

Type 1 diabetes#

Type 1 diabetes is caused by an autoimmune destruction of the insulin-making cells in the pancreas, which means insulin is no longer produced. It was once called juvenile diabetes or insulin-dependent diabetes mellitus, although these terms are no longer commonly used. It is one of the most common chronic childhood illnesses and most often develops in people under 30, though it can occur at any age.

There is no cure, but type 1 diabetes can be managed successfully with insulin injections, nutrition and exercise. If a person with type 1 diabetes skips a meal, exercises heavily or takes too much insulin, their blood glucose can fall too low. Symptoms of low blood glucose include tremor, sweating, dizziness, hunger, headache and a change in mood. This can be treated with a quick source of sugar, such as glucose tablets or sweets, followed by something more substantial such as fruit. People with type 1 diabetes should keep rapidly absorbed carbohydrate on hand at all times, just in case.

Type 2 diabetes#

Type 2 diabetes is the most common form, affecting 85 to 90% of all people with diabetes. It is sometimes described as a lifestyle condition because it is more common in people who are overweight or obese, especially those carrying excess weight around the waist, and who do not get enough physical activity. It is strongly associated with high blood pressure and abnormal cholesterol levels.

Type 2 diabetes usually affects adults over 40, but younger people are increasingly being diagnosed as rates of overweight and obesity rise. It was once called non-insulin-dependent or mature-onset diabetes. Research shows that type 2 diabetes can often be prevented or delayed with lifestyle changes.

Gestational diabetes#

Gestational diabetes affects around 3 to 8% of pregnant women. Higher-risk groups include women over 30, women with a family history of type 2 diabetes, women who are overweight or obese, and women from certain ethnic backgrounds. After the baby is born, the mother’s blood glucose usually returns to normal, although she has a greater risk of developing type 2 diabetes later in life.

If the mother’s blood glucose stays raised, the baby may grow larger than normal, and after delivery the baby may have low blood glucose, particularly if levels were high before the birth. The baby will not be born with diabetes. With monitoring and treatment, and good blood glucose control, these risks are greatly reduced.

Pre-diabetes#

Pre-diabetes has no symptoms but carries a range of risk factors, including obesity, smoking, heart disease, polycystic ovarian syndrome and high blood pressure. Without treatment, about one in three people with pre-diabetes will go on to develop type 2 diabetes.

Diabetes insipidus#

Diabetes insipidus is caused by insufficient vasopressin, a hormone produced by the brain that signals the kidneys to conserve water. Without enough vasopressin, too much water is lost in the urine, and the person drinks large amounts of fluid to try to keep up. In severe cases, a person may pass up to 30 litres of urine a day. Without treatment, it can cause dehydration and a dangerous rise in the concentration of salts, particularly sodium, in the blood.

The name is a little misleading: apart from the symptoms of thirst and passing large volumes of urine, diabetes insipidus has nothing to do with the diabetes caused by high blood sugar. Depending on the cause, it can be treated with medications, vasopressin replacement and a low-salt diet.

Complications#

High blood glucose levels can lead to serious complications, including:

• kidney damage (nephropathy)
• eye damage (retinopathy)
• nerve damage to the feet and other parts of the body (neuropathy)
• foot ulcers or infections resulting from circulation problems
• heart disease (such as angina, heart attacks or heart failure), strokes and circulation problems in the legs
• sexual difficulties, including erectile dysfunction

Tests for diabetes#

The fasting blood glucose test is the most common diagnostic test. It measures the amount of glucose in the blood after a period without eating, and is usually done before breakfast. Other tests include the oral glucose tolerance test, the random blood glucose test and the glycosylated haemoglobin (HbA1c) test.

People at risk should have a laboratory blood glucose test, ordered by a doctor rather than done on a portable home meter, to check whether they have diabetes. It is important not to wait for symptoms to appear, as they may not develop until blood glucose is already quite high. See your doctor for a diabetes test.

Treatment and self-care#

Treatment aims to prevent complications by keeping blood glucose, blood pressure and cholesterol within a healthy range and by achieving a healthy body weight. Management depends on the type of diabetes, but can include:

• for type 1: taking insulin daily by injection or insulin pump, matching food intake to insulin and exercise, and self-monitoring of blood glucose
• for type 2: regular physical activity, weight management, stopping smoking, and medications (and potentially insulin later)
• increasing the amount of slowly absorbed carbohydrates, such as beans and fruit, which take longer to digest
• having regular checks for possible complications

To manage type 2 diabetes day to day:

• check your blood glucose levels regularly
• use any medication strictly as prescribed, and don’t change your diabetes tablets without talking to your doctor first
• be physically active as often as you can, and sit less
• choose healthy foods in suitable amounts
• seek medical advice if you feel unwell
• look after your mental wellbeing, and seek advice if you feel anxious or depressed
• consider joining a support group, and link up with the diabetes team in your area through your doctor or a diabetes organisation

There are several risk factors for type 2 diabetes that you can do something about, including:

• being overweight or obese, especially around the waist
• low levels of physical activity
• unhealthy eating habits, such as regularly choosing high-fat, high-sugar, high-salt or low-fibre foods
• cigarette smoking

Key points#

• Diabetes occurs when blood glucose is too high because of a problem with insulin; the body uses glucose as its main source of energy.
• High blood glucose levels cause the health problems linked to diabetes, known as complications.
• Ketoacidosis is a medical emergency; seek immediate medical advice if its symptoms occur.
• Type 2 diabetes can often be prevented or delayed, and is managed with healthy eating, activity, weight management and, if needed, medication or insulin.

Where to get help and trusted information#

For evidence-based global health guidance, see Source: World Health Organization (WHO).