Introduction 

Diabetes is a lifelong condition that causes a person's blood sugar (glucose) level to become too high.

The hormone insulin – produced by the pancreas – is responsible for controlling the amount of glucose in the blood.

There are two main types of diabetes:

• Type 1 – where the pancreas doesn't produce any insulin
• Type 2 – where the pancreas doesn't produce enough insulin or the body’s cells don't react to insulin

This topic is about type 1 diabetes. Read more about type 2 diabetes.

Another type of diabetes, known as gestational diabetes, occurs in some pregnant women and tends to disappear following birth.

It's very important for diabetes to be diagnosed as soon as possible, because it will get progressively worse if left untreated.

You should therefore visit your GP if you have symptoms, which include feeling thirsty, passing urine more often than usual and feeling tired all the time (see the list below for more diabetes symptoms). 

Type 1 and type 2 diabetes

Type 1 diabetes can develop at any age, but usually appears before the age of 40, particularly in childhood. Around 10% of all diabetes is type 1, but it's the most common type of childhood diabetes. This is why it's sometimes called juvenile diabetes or early-onset diabetes. 

In type 1 diabetes, the pancreas (a small gland behind the stomach) doesn't produce any insulin – the hormone that regulates blood glucose levels. This is why it's also sometimes called insulin-dependent diabetes.

If the amount of glucose in the blood is too high, it can, over time, seriously damage the body's organs.

In type 2 diabetes, the body either doesn't produce enough insulin to function properly, or the body's cells don't react to insulin. Around 90% of adults with diabetes have type 2, and it tends to develop later in life than type 1.

Diabetes symptoms

The symptoms of diabetes occur because the lack of insulin means that glucose stays in the blood and isn’t used as fuel for energy.

Your body tries to reduce blood glucose levels by getting rid of the excess glucose in your urine.

Typical symptoms include:

• feeling very thirsty
• passing urine more often than usual, particularly at night
• feeling very tired
• weight loss and loss of muscle bulk

The symptoms of type 1 diabetes usually develop very quickly in young people (over a few days or weeks). In adults, the symptoms often take longer to develop (a few months).

Read more about the symptoms of type 1 diabetes.

Causes of type 1 diabetes 

Type 1 diabetes occurs as a result of the body being unable to produce insulin, which moves glucose out of the blood and into your cells to be used for energy.

Without insulin, your body will break down its own fat and muscle, resulting in weight loss. This can lead to a serious short-term condition called diabetic ketoacidosis, where the bloodstream becomes acidic and you develop dangerous levels of dehydration.

Type 1 diabetes is an autoimmune condition, where the immune system (the body's natural defence against infection and illness) mistakes the cells in your pancreas as harmful and attacks them.

Read more about the causes of type 1 diabetes.

Treating type 1 diabetes

It's important that diabetes is diagnosed as early as possible, so that treatment can be started.

Diabetes can't be cured, but treatment aims to keep your blood glucose levels as normal as possible and control your symptoms, to prevent health problems developing later in life.

If you're diagnosed with diabetes, you'll be referred to a diabetes care team for specialist treatment and monitoring.

As your body can't produce insulin, you'll need regular insulin injections to keep your glucose levels normal. You'll be taught how to do this and how to match the insulin you inject to the food you eat, taking into account your blood glucose level and how much exercise you do.

Insulin injections come in several different forms, with each working slightly differently. Some last up to a whole day (long-acting), some last up to eight hours (short-acting) and some work quickly but don't last very long (rapid-acting). You'll most likely need a combination of different insulin preparations.

There are alternatives to insulin injections, but they're only suitable for a small number of patients. They are:

• insulin pump therapy – where a small device constantly pumps insulin (at a rate you control) into your bloodstream through a needle that's inserted under the skin
• islet cell transplantation – where healthy insulin-producing cells from the pancreas of a deceased donor are implanted into the pancreas of someone with type 1 diabetes (read about the criteria for having an islet transplant)
• a complete pancreas transplant

Read more about diagnosing diabetes and treating type 1 diabetes.

Complications

If diabetes is left untreated, it can cause a number of different health problems. Large amounts of glucose can damage blood vessels, nerves and organs.

Even a mildly raised glucose level that doesn't cause any symptoms can have damaging effects in the long term.

Read more about the complications of type 1 diabetes.

Living with diabetes

If you have type 1 diabetes, you'll need to look after your health very carefully. Caring for your health will also make treating your diabetes easier and minimise your risk of developing complications.

For example, eating a healthy, balanced diet and exercising regularly will lower your blood glucose level. Stopping smoking (if you smoke) will also reduce your risk of developing cardiovascular disease.

If you have diabetes, your eyes are at risk from diabetic retinopathy, a condition that can lead to sight loss if it's not treated. Everyone with diabetes aged 12 or over should be invited to have their eyes screenedonce a year.

Read more about living with diabetes.