Type 1 diabetes

Diabetes is a lifelong condition that causes a person's blood sugar (glucose) level to become too high. It's important for diabetes to be diagnosed as soon as possible because it will get worse if left untreated.

Types of diabetes 

The hormone insulin, produced by the pancreas, controls 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

Symptoms of type 1 diabetes 

Typical symptoms of type 1 diabetes 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). It starts most commonly in childhood, with two peaks, between the ages of 6 months to 5 years old, and again during puberty.

In adults, the symptoms often take longer to develop (a few months).

These symptoms 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. It does this by getting rid of the excess glucose in your urine.

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

See your GP if you think you may have diabetes.

When to seek urgent medical attention 

You should seek urgent medical attention if you have diabetes and develop:

  • a loss of appetite
  • nausea or vomiting
  • a high temperature
  • stomach pain
  • fruity smelling breath – which may smell like pear drops or nail varnish (others will usually be able to smell it, but you won't)

Hypoglycaemia (low blood glucose) 

If you have diabetes, your blood glucose levels can become very low. This is known as hypoglycaemia (or a 'hypo'), and it's triggered when injected insulin in your body moves too much glucose out of your bloodstream.

In most cases, hypoglycaemia occurs as a result of taking too much insulin, although it can also develop if you skip a meal, exercise very vigorously or drink alcohol on an empty stomach.

Symptoms of a 'hypo' include:

  • feeling shaky and irritable
  • sweating
  • tingling lips
  • feeling weak
  • feeling confused 
  • hunger
  • nausea (feeling sick)

A hypo can be brought under control simply by eating or drinking something sugary.

If it isn't brought under control, a hypo can cause confusion, slurred speech and eventually unconsciousness.

In this case, an emergency injection of a hormone called glucagon will be needed. Glucagon increases the glucose in your blood.

Hyperglycaemia (high blood glucose) 

As people with type 1 diabetes cannot produce any insulin, their blood glucose levels may become very high.

When your blood glucose levels become too high, it's known as hyperglycaemia. The symptoms of hyperglycaemia may come on suddenly and include:

  • extreme thirst
  • a dry mouth
  • blurred vision
  • drowsiness
  • a need to pass urine frequently 

Left untreated, hyperglycaemia can lead to diabetic ketoacidosis. This is a serious condition where the body breaks down fat and muscle as an alternative source of energy.

This leads to a build-up of acids in your blood, which can cause vomiting, dehydration, unconsciousness and even death. The presence of ketones produces the ‘fruity smelling breath’, which is characteristic of diabetic ketoacidosis.

Diagnosis of type 1 diabetes 

It's important for diabetes to be diagnosed early so treatment can be started as soon as possible.

If you experience the symptoms of diabetes, visit your GP as soon as possible. They'll ask about your symptoms and may request blood and urine tests.

Your urine sample will be tested for glucose. Urine doesn't normally contain glucose, but glucose can pass from the kidneys into your urine if you have diabetes.

If your urine contains glucose, a specialised blood test known as glycated haemoglobin (HbA1c) can be used to determine whether you have diabetes.

Causes of type 1 diabetes 

Type 1 diabetes is most commonly caused by an autoimmune condition. This means your immune system (body’s way of protecting itself from things that invade it)  attacks healthy body tissue by mistake. In this case, it attacks the cells in your pancreas.

Your damaged pancreas is then unable to produce insulin. So, glucose cannot be moved out of your bloodstream and into your cells.

Type 1 diabetes is often inherited (runs in families), so the autoimmune reaction may be genetic.

It's not known exactly what triggers the immune system to attack the pancreas. Some research has suggested it may be a viral infection. Other research suggests dietary factors may be a trigger.

Treating type 1 diabetes 

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

If you're diagnosed with type 1 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 will be given a plan of treatment suited to your individual needs, as well as advice on a healthy diet and lifestyle. This will promote good control of your blood glucose and prevent complications.

Complications of type 1 diabetes 

Short term problems can occur if your blood sugar is too low, causing hypoglycaemia, or ‘hypos’ (see section above). If your blood sugar is too high, you can develop a condition called ketoacidosis. Both conditions are serious, and can lead to hospital admission.

Diabetes can cause serious long-term health problems. It's the most common cause of vision loss and blindness in people of working age.

Everyone with diabetes aged 12 or over should be invited to have their eyes screened once a year for diabetic retinopathy.

Diabetes is the reason for many cases of kidney failure and lower limb amputation.

People with diabetes are up to five times more likely to have circulatory disease, such as a stroke or heart problems, than those without diabetes.

Other effects of poorly controlled diabetes include loss of sensation, skin ulceration, and increased risk of infection. Good control of blood glucose is essential in order to avoid complications, and promote a normal life expectancy.

Living with type 1 diabetes 

If you have type 1 diabetes, you'll need to look after your health very carefully. This means:


The information on this page has been adapted from original content from the NHS website.

For further information see terms and conditions.

This page was reviewed January 2019

This page is due for review September 2021

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