What is type 1 diabetes?

Diabetes, correctly called diabetes mellitus, is a disorder of carbohydrate (glucose, or sugar) metabolism. In type 1 diabetes, the pancreas can no longer produce the hormone insulin. Insulin is produced by the beta cells of the pancreas; it is secreted in response to an increased level of glucose in the blood, and is vital in controlling this level. A person with diabetes cannot control their blood glucose and they become hyperglycaemic – meaning they have abnormally high levels of blood glucose.

What causes it?

By the time a person with type 1 diabetes experiences symptoms, almost all the beta cells in the pancreas have been destroyed. This destruction is likely because of an autoimmune process in which the body produces antibodies that attack its own cells.

There may be a genetic tendency for the disease, which is then triggered by an environmental event such as a viral infection. The third step in the process is inflammation of the pancreas called insulitis. The fourth step is alteration in the surface of the beta cell so that it is no longer recognised as part of the body, but is perceived by the immune system to be a foreign cell. The fifth step is the development of an immune response.

The end result is the destruction of beta cells and the development of diabetes.

Who gets it?

Diabetes currently affects about 347 million people worldwide. Type 1 diabetes comprises about 10-15% of all cases.

Type 1 diabetes usually begins before age 40, with peak incidence around age 14.

A strong family history is a definite risk factor for type 1 diabetes, although the way in which the disease is inherited is not clear.

Symptoms and signs

Characteristic symptoms of diabetes:

    • Excessive thirst

    • Weight loss

    • Excessive urination

    • Tiredness

Symptoms may be quite sudden, developing over a few days.

The first sign of type 1 diabetes can also be a kind of coma called acidotic coma. This is a result of a life-threatening event called diabetic ketoacidosis in which levels of glucose in the blood are extremely high. Because of a lack of insulin, the glucose in the blood cannot enter the cells where it is desperately needed.

To prevent starvation and cell death, lipids (fats) are converted to acidic substances called ketones. Ketones can be used as food by the cells, even in the absence of insulin. However, the acidic ketones can also cause ketoacidosis: in this condition, the blood and tissues become more acidic than normal, which may lead to malfunctioning of organs such as the heart. Initially, a person with ketoacidosis automatically compensates by breathing deeply (called Kussmaul breathing), but later this mechanism cannot cope with the acidic load caused by the ketones.

Patients feel unwell and nauseous and may vomit. There is increased urine production and if the condition is not recognised and treated, the person becomes drowsy and eventually comatose. This is usually in response to an infection, surgery or stress.


Diabetes is diagnosed by measuring the levels of glucose in the blood. The normal fasting levels (blood glucose measured before breakfast) are between 4 and 6 mmol/l. You may be diagnosed with diabetes if a fasting blood test result is at or above 7.0mmol/l or a random blood test result is at or above 11.1mmol/l.

If a person first shows signs of diabetes by developing diabetic ketoacidosis, then the diagnosis may be more difficult since this must be distinguished from other causes of decreased levels of consciousness. The presence of ketones in the blood is a strong indicator that the cause is diabetes.

What is the outcome for people with diabetes?

Diligent control of blood glucose by attention to lifestyle and treatment with insulin generally leads to a good outcome, although complications usually occur with time.

Tight control of blood glucose achieved by regular measurements throughout the day, which are then used to determine an exact insulin dose, leads to fewer complications, and later onset of these.

When to see your doctor

Consult your doctor if you develop:

    • Excessive thirst

    • Excessive urination

    • Weight loss

    • Genital itch

If you have a family history of diabetes, see your doctor as soon as possible.

If you are already diabetic and you develop these symptoms, it is an indication your blood glucose is out of control and you should see your doctor immediately.


Type 1 diabetes is managed with insulin replacement through lifelong insulin injections, by following a healthy diet and eating plan, by getting regular exercise and monitoring blood glucose levels regularly.

The aim of treating your diabetes is to keep blood glucose levels as close to 'normal' as possible, that is between 4 to 6 mmol/L (fasting).

Keeping blood glucose levels in a healthy range will help prevent both short-term and long-term complications.

Insulin doses are best worked out by the prescribing doctor. Note that every diabetic has their own appropriate dose. You cannot compare your dose to that of another diabetic as his or her circumstances and medical profile may be very different to yours.

Hypoglycaemia (low blood glucose) is a complication of insulin therapy, with the number of attacks increasing with tighter control. The cause of hypoglycaemia should always be investigated and appropriate action should be taken to prevent further episodes.

Apart from diabetic control, all other risk factors for heart and blood vessel disease should be carefully monitored and treated. These risk factors often go hand-in-hand with diabetes, and include dyslipidaemia (abnormal levels of fats in the body) and hypertension (high blood pressure).

Diet and lifestyle

All type 1 diabetics need to see a dietitian so that correct, healthy eating patterns can be implemented. Healthy eating implies a high-fibre, low-saturated-fat diet, which limits high-cholesterol foods, and which includes lean protein from fish, poultry and legumes.

Apart from providing guidelines on what to eat, a dietitian can also help to establish the amount of energy required in the diet, and teach the diabetic how to do carbohydrate counting.

As smoking can have a dramatic impact on cardiovascular health, diabetics are strongly urged to quit. Doctors can provide guidance in terms of smoking-cessation aids, such as nicotine replacement therapy (patches, inhalers, gum) and/or prescription medication.

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