Type 1 diabetes

This factsheet is for people who have type 1 diabetes, or who would like information about it.

Type 1 diabetes is a lifelong condition in which the body can't control levels of glucose in the blood. It develops when the body can’t produce the hormone insulin. Type 1 diabetes is sometimes called insulin-dependent diabetes.

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About type 1 diabetes

Type 1 diabetes can develop at any age, but usually affects people before the age of 40, and most commonly during childhood. It develops when your body can’t produce the hormone insulin. Insulin regulates the level of glucose in your blood. Glucose is a simple form of sugar found in foods and sugary drinks. It's absorbed by your body as a natural part of digestion and is carried around your body in your blood. When glucose reaches your body tissues, such as muscle cells, it's absorbed and converted into energy.

Insulin is secreted into your blood by your pancreas, which is a gland located behind your stomach. A shortage of insulin causes glucose to build up in your blood.

Causes of type 1 diabetes

Type 1 diabetes develops when the cells in your pancreas that make insulin (beta cells) are destroyed by your body's immune system. Because of this, type 1 diabetes is known as an autoimmune disease. However, the way in which type 1 diabetes first starts isn’t fully understood at present, though it's possible it may be caused by a virus or run in families.

Monitoring your blood glucose level

You can use a home test kit to monitor your blood glucose level. This involves regularly taking a pinprick of blood from the side of your fingertip and putting a drop on a testing strip. A meter will read the result automatically.

Your 'normal' blood glucose range will be specific to you but a general guide for adults is:
  • before meals: 4 to 7mmol/L
  • after meals: less than 9mmol/L
  • Your doctor will show you how to monitor your blood glucose levels and tell you how often you need to check it.
You may also need to have your levels of glycosylated haemoglobin (HbA1C) tested at least twice a year. HbA1C is a protein that is produced when you have high blood glucose levels over a long period of time. The HbA1C test is done by taking blood from a vein in your arm or sometimes a drop of blood from a finger-prick. It’s used to see how well you’re controlling your blood sugar levels.

Symptoms and diagnosis

Symptoms and diagnosis

Symptoms of type 1 diabetes

If you have type 1 diabetes, you may:

  • pass more urine than usual
  • be constantly thirsty
  • have unexplained weight loss
  • be extremely tired
  • have blurred vision
  • be irritable
The symptoms can develop quickly, usually over a few weeks.

If you have any of these symptoms, see a doctor.

Diagnosis of type 1 diabetes

The doctor will ask about your symptoms and examine you. He or she may also ask about your medical history.

You may need to have some of the following tests.

  • Urine test. You will need to give a sample to be tested for glucose and ketones.
  • Fasting blood glucose test. Your doctor will arrange for you to have a sample of blood taken from your arm to test for glucose.
If your urine tests positively for ketones and you have a raised blood glucose level, this suggests a diagnosis of type 1 diabetes.

Please note that availability and use of specific tests may vary from country to country



If type 1 diabetes isn't diagnosed or controlled properly, you can develop blood glucose levels that are either too high (hyperglycaemia) or too low (hypoglycaemia).


Your blood glucose levels can become too high if you’re stressed or unwell, your insulin dose is too low, you miss doses, or if you eat too much carbohydrate. Hyperglycaemia can cause you to be more thirsty than usual, feel tired and have headaches.

Rarely, glucose can build up in your blood and reach dangerous levels. This is called diabetic ketoacidosis. It can cause you to vomit, breathe faster than normal and have breath that smells of ketones (like pear drops or nail varnish). Diabetic ketoacidosis is a medical emergency and can be fatal if you aren’t treated in hospital immediately.

In the long-term, hyperglycaemia can increase your risk of:

  • kidney failure
  • nerve damage
  • blindness
  • heart disease
  • stroke


Your blood glucose levels can become too low if you don't eat enough foods that contain glucose, take too much insulin, or do more physical activity than usual. Hypoglycaemia can cause you to feel faint, sweaty, confused and you may feel your heart pounding. It should be treated straight away with glucose tablets (or a few sweets/sugary drink), followed by about two to three biscuits or a sandwich. If hypoglycaemia is left untreated you may become unconscious and if severe it can be fatal.



There isn't a cure for type 1 diabetes but it can be controlled with medicines and lifestyle changes and monitored with blood tests.


Type 1 diabetes is controlled by giving your body insulin. This helps glucose to be absorbed into your cells and converted into energy, which stops it building up in your blood.

There are two main ways of taking insulin.

  • Insulin injections. These are the most common form of treatment, where you inject insulin under your skin. You will usually inject yourself before meals, using either a small needle or a pen-type syringe with replaceable cartridges.
  • Portable insulin pumps. These may be appropriate if you find it difficult to control your blood glucose with regular injections, despite careful monitoring. Insulin pumps can be programmed to inject you with insulin at a rate that you can control.
There are several different kinds of insulin that work at different rates and act for different lengths of time. Ask your doctor for advice on which type and method is best for you.

Availability and use of different treatments may vary from country to country. Ask your doctor for advice on your treatment options.


By making the following lifestyle changes, you can help control your blood glucose levels.

  • Eat a healthy balanced diet with regular meals, three times a day. Include carbohydrates, such as pasta or potatoes in each meal. But if you have hypoglycaemia from time to time, it's a good idea to keep some sugary food or glucose tablets with you.
  • Try to do at least half an hour of moderate physical activity on at least three days a week. This will help you to stay a healthy weight and control your blood glucose levels.
  • Only drink alcohol in moderation and stick within the recommended daily limits.
  • If you smoke, give up. Smoking is unhealthy for everyone, but it's especially important to stop if you have diabetes because you already have an increased risk of developing circulatory problems and cardiovascular disease. Smoking makes the chance of you developing these diseases even greater.



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  • Gestational diabetes. Physiological effects of pregnancy on glucose metabolism. GP Notebook. www.gpnotebook.co.uk, accessed 18 September 2009
  • What is gestational diabetes? A guide. Diabetes UK. www.diabetes.org.uk, accessed 18 September 2009
  • Gestational diabetes. GP Notebook. www.gpnotebook.co.uk, accessed 18 September 2009
  • Polycystic ovary syndrome (PCOS): what it means for your long-term health. Royal College of Obstetricians and Gynaeocologists. www.rcog.org.uk, accessed 18 September 2009
  • Hypoglycaemia. GP Notebook. www.gpnotebook.co.uk, accessed 18 September 2009
  • A difficult birth: what is shoulder dystocia? Royal College of Obstetricians and Gynaeocologists. www.rcog.org.uk, accessed 18 September 2009
  • The Glycaemic Index. Diabetes UK. www.diabetes.org.uk , accessed 18 September 200

This information was published by Bupa's Health Information Team and is based on reputable sources of medical evidence. It has been peer reviewed by Bupa doctors. Photos and videos are only for illustrative purposes and do not reflect every presentation of a condition. The content is intended for general information only and does not replace the need for personal advice from a qualified health professional.

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