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Type 1 diabetes

Key points

  • About 2.9 million people in the UK have diabetes – 15 out of every 100 of these people have type 1 diabetes.
  • Type 1 diabetes is a lifelong condition and usually develops at a young age.
  • Type 1 diabetes occurs when your body can't produce insulin, which means it can't control the level of glucose in your body.
  • Type 1 diabetes can be controlled by taking insulin. Injections are the most common form of treatment.

Featured FAQ

How important is it to prevent low blood glucose?

It's very important to keep your blood glucose levels as stable as possible if you have type 1 diabetes. If you don’t monitor your condition regularly and your blood glucose levels get low, you may become very unwell.

See all our FAQs on type 1 diabetes

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

About type 1 diabetes

About 2.9 million people in the UK have been diagnosed with diabetes. There are two main types of diabetes: type 1 and type 2. Type 1 diabetes is the rarer form, affecting 15 out of every 100 people (including children) with diabetes. You may also hear type 1 diabetes called insulin-dependent diabetes and sometimes juvenile-onset diabetes.

Type 1 diabetes can develop at any age, but usually begins during childhood or adolescence.

Type 1 diabetes develops when your body can’t produce insulin. Insulin is a hormone (a chemical produced naturally by your body) that 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, for example your muscle cells, insulin helps it enter the tissue where it's converted into energy.

Insulin is produced by your pancreas, which is a gland located behind your stomach. A shortage of insulin causes glucose to build up in your blood. This means your blood sugar levels become too high.

Illustration of the liver and surrounding structures

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

The symptoms can develop quickly, usually over a few weeks. If you have any of these symptoms, see your GP.

Complications of type 1 diabetes

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 you eat too much carbohydrate. Hyperglycaemia can cause you to be more thirsty than usual, feel tired and have headaches.

In some people who have diabetes, glucose can build up in the blood and reach dangerous levels. This is called diabetic ketoacidosis. It can cause you to vomit, breathe faster than usual and give your breath a distinctive smell, similar to pear drops or nail varnish. Diabetic ketoacidosis is a medical emergency and can be fatal if you aren’t treated in hospital immediately.

If your blood sugar is raised for a number of years, it can increase your risk of:

  • kidney failure
  • nerve damage
  • blindness
  • heart disease
  • stroke
  • foot ulcers – leading to foot or lower leg amputation


Your blood glucose levels can become too low if you don't eat enough foods that contain glucose. It can also drop too low if you take too much insulin or do more physical activity than usual. Hypoglycaemia (also known as a ‘hypo’) can cause you to feel faint, sweaty, confused and you may feel your heart pounding. Treat it straight away by eating glucose tablets (or a few sweets or a sugary drink), followed by a couple of biscuits or a sandwich.

If you don't treat hypoglycaemia, you may have fits and become unconscious, and if it’s very severe, hypoglycaemia can be fatal. For more information, see our frequently asked questions.

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. The reasons why your body’s immune system does this aren’t fully understood at present, but it's possible that environmental or genetic factors may trigger the attack.

Diagnosis of type 1 diabetes

Your GP will ask about your symptoms and examine you. You’re likely to have a number of tests, including:

  • a urine test – this will be checked for glucose and ketones
  • a fingerprick test – this is also known as a random glucose test and involves taking a sample of your blood to test how much glucose it contains
  • a fasting blood glucose test – you will need to have this test at a time when you haven’t eaten anything for at least eight hours beforehand

If your urine tests positively for ketones and you have a raised blood glucose level, this suggests a diagnosis of type 1 diabetes.

If you're diagnosed with type 1 diabetes, you will usually be referred to a clinic that has nurses and doctors who specialise in treating diabetes.

Treatment of type 1 diabetes

There isn't a cure for type 1 diabetes but you can control it with medicines and lifestyle changes. You will need to monitor your blood glucose level carefully.


Type 1 diabetes is controlled by taking insulin. This helps glucose to be absorbed into your cells where it’s 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 or diabetes specialist nurse for advice on which type and method is best for you. For more information, see our frequently asked questions.


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. If you have hypoglycaemia from time to time, it's a good idea to keep some sugary food or glucose tablets with you.
  • Aim to do 150 minutes of moderate exercise over a week in bouts of 10 minutes or more. 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, stop. Smoking is unhealthy for everyone, but it's especially important to stop if you have diabetes. This is because you already have an increased risk of developing circulatory problems and cardiovascular disease. Smoking further increases your risk of developing these diseases.

Ask at your clinic whether they run structured education classes such as DAFNE (Dose Adjustment For Normal Eating). This is a five-day intensive course that helps you learn how to adjust your insulin dose.

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/litre
  • two hours after meals: less than 9mmol/litre

Your GP or diabetes specialist nurse will show you how to monitor your blood glucose level. He or she will also tell you how often you need to check it.

You may also need to have your levels of glycosylated haemoglobin (HbA1C) tested at least once 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 fingerprick. It’s used to see how well you’re controlling your blood sugar levels.


Reviewed by Pippa Coulter, Bupa Health Information Team, June 2013.

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For answers to frequently asked questions on this topic, see FAQs.

For sources and links to further information, see Resources.

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  • This information was published by Bupa's Health Information Team and is based on reputable sources of medical evidence. It has been reviewed by appropriate medical or clinical professionals. Photos are only for illustrative purposes and do not reflect every presentation of a condition. The content is intended only for general information and does not replace the need for personal advice from a qualified health professional. For more details on how we produce our content and its sources, visit the about our health information page.

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