What are the warning signs of diabetes?

In the UK, around 4.7 million people are known to have diabetes mellitus, and it is thought at least a million more people have the condition without being aware of it. This is because the most common form of the condition (known as Type 2 diabetes) may produce only mild symptoms, so it can easily be overlooked.

Diabetes mellitus is the most common disorder affecting the glands of the endocrine system. It is caused by a shortage or lack of the hormone insulin produced by the pancreas. The body uses insulin to absorb glucose into cells, and a deficiency leads to abnormally high levels of glucose in the blood and the urine. This causes problems and defects in various parts of the body.

There are two main types of diabetes mellitus:

Genes play a part in both types of diabetes mellitus, but environmental factors are thought to be the triggers. Of the people who inherit the genes for Type 1 diabetes, only a small proportion actually develop the condition. 

Many people newly diagnosed with Type 1 diabetes have antibodies to a protein found in cow's milk, leading some researchers to suggest that feeding babies with formula milk may trigger the immune system to destroy pancreatic cells. It is thought more likely that Type 1 diabetes occurs as a result of a viral infection that damages the pancreas.

Type 2 is by far the most common form of diabetes mellitus. Risk factors include a family history of diabetes, increasing age and being of Asian or Afro-Caribbean origin. Being overweight, particularly if you store fat around the waist, is another risk factor as obesity is known to increase insulin resistance. Weight loss and keeping active reduce insulin resistance.

Globally, the number of people who have this form of diabetes is rising. This is attributed to the fact that people in the developed world are increasingly inactive and overweight.

The following symptoms are associated with uncontrolled Type 1 and Type 2 diabetes due to excessive levels of glucose in the blood (hyperglycaemia). People with Type 2 diabetes may experience only some of the symptoms, or only in a mild form, leading many to be unaware that they have the condition.

Diabetes is diagnosed by a blood test to check for glucose. A urine sample may be taken and a glucose-tolerance test may also be performed. Type 1 diabetes is more easily identified than Type 2, which may go undetected for between nine and twelve years.

People with Type 1 diabetes always need to inject insulin because their body is unable to make the hormone. They inject up to five times a day, depending on their lifestyle. They also need to follow a balanced diet to ensure that their blood sugar levels do not fluctuate too widely.

Initially, people with Type 2 diabetes are often able to control their symptoms with regular injections of insulin. Diet, regular exercise, weight loss (if necessary) and oral medication to help the body utilize insulin more efficiently all play a part in managing the condition. As the condition progresses, people may have to rely on insulin injections to balance their blood sugar.

Possible future alternatives to injected insulin include nasal and oral sprays, patches, tablets and inhalers.

Most people with diabetes lead a healthy life. However, there is a risk of serious complications if the condition is not tightly controlled. A short-term risk in Type 1 diabetes is ketoacidotic coma. This is the result of the body breaking down fat and muscle to create energy normally provided by glucose.

Both types of diabetes can lead to complications from the effects of persistently raised levels of blood glucose on the body's blood vessels and nerves. These include coronary heart disease, stroke and kidney disease, as well as nerve damage and lack of blood supply to the feet, which in severe cases can result in amputation.

Diabetic retinopathy, a disease of the retina, can lead to blindness. It is the most common cause of blindness in people aged 20–65 in the UK.

Gestational diabetes mellitus (GDM) affects a small number of pregnant women. It usually develops during the second or third trimester as a result of the body's failure to produce enough insulin to meet the extra demands of pregnancy. Although blood glucose levels usually return to normal after delivery, women who have had GDM have a higher risk of developing Type 2 diabetes in later life.

Pregnant women with diabetes must control their blood glucose level prior to conception and throughout pregnancy to avoid the risk of complications. Too much glucose in the bloodstream increases the risk of malformation. In addition, the baby may grow too big and need to be delivered by Caesarean section.

Diabetes insipidus is a completely separate disorder from diabetes mellitus. The similar names derive from the fact that excessive urination is a symptom of both (diabetes means overflow). Thirst is the other main symptom. In diabetes insipidus these symptoms are caused by an imbalance of antidiuretic hormone (ADH), or vasopressin, which is stored in the pituitary gland and maintains the fluid balance within the body.

There are four types. Neurogenic diabetes insipidus is caused by a deficiency of ADH, while the nephrogenic form is caused by an inability of the kidneys to respond to ADH. The third type, gestagenic, appears during pregnancy and the fourth, called dipsogenic, is caused by abnormal thirst and excessive intake of fluids.

The treatment depends on the cause. In some types, a synthetic form of ADH is taken in a nasal spray or tablet. For sufferers of the dipsogenic form of the disease, the only treatment is limitation of fluid intake with, occasionally, a small dose of synthetic ADH at night.

People with diabetes should pay careful attention to diet and activity levels. The diet should be the same as is recommended for general health, with plenty of fresh fruit and vegetables, wholegrain cereals and pulses, some low-fat protein, less saturated fat (choose polyunsaturated and monounsaturated varieties), and a minimum of fatty, sugary foods and salt.

Eating regularly helps to maintain stable blood glucose levels, and regular exercise is important for managing the diabetes. It can also help to control blood glucose and blood pressure, strengthen the heart and lungs and aid weight control.

If blood glucose levels fall abnormally low, diabetics may lapse into unconsciousness. People with Type 1 diabetes may inadvertently take too much insulin, eat too little or exercise too much. The glucose level in their blood may then drop to an abnormally low level (hypoglycaemia).

Signs of oncoming hypoglycaemia include faintness, palpitations, sweating, breathlessness and confused or violent behaviour.

Sugary food or drink remedies the situation and should be followed by a starchy snack such as a sandwich, or a meal if it is due. Type 1 diabetics should always carry a sugary snack in case of emergency. If the person falls into unconsciousness, seek medical help immediately.

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