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

There are two main types of diabetes – type 1 diabetes and type 2 diabetes.

Type 2 diabetes is far more common than type 1. In the UK, around 90% of all adults with diabetes have type 2.

There are 4.7 million people living with diabetes in the UK. That's more than one in 15 people in the UK who has diabetes (diagnosed or undiagnosed).

This figure has nearly trebled since 1996, when there were 1.4 million. By 2025, it is estimated that 5 million people will have diabetes in the UK.


Many more people have blood glucose levels above the normal range, but not high enough to be diagnosed as having diabetes.

This is sometimes known as prediabetes. If your blood glucose level is above the normal range, your risk of developing full-blown diabetes is increased.

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

When to see a doctor

You should therefore visit your GP as soon as possible if you have symptoms, such as feeling thirsty, passing urine more often than usual, and feeling tired all the time.

It's also advised to see your GP if you have risk factors of diabetes and are worried about developing diabetes in future.

Symptoms of diabetes

The main symptoms of diabetes are:

  • feeling very thirsty
  • urinating more frequently than usual, particularly at night
  • feeling very tired
  • weight loss and loss of muscle bulk
  • itching around the penis or vagina, or frequent episodes of thrush
  • cuts or wounds that heal slowly
  • blurred vision

Type 1 diabetes can develop quickly over a few hours or even days.

Many people have type 2 diabetes for years without realising because the early symptoms tend to be general.

What causes diabetes?

The amount of glucose in the blood is controlled by a hormone called insulin, which is produced by the pancreas (a gland behind the stomach).

When food is digested and enters your bloodstream, insulin moves glucose out of the blood and into cells, where it's broken down to produce energy.

However, if you have diabetes, your body is unable to break down glucose into energy. This is because there's either not enough insulin to move the glucose, or the insulin produced doesn't work properly.

Type 1 diabetes

In type 1 diabetes, the body's immune system attacks and destroys the cells that produce insulin. As insulin production decreases until no more is produced, your glucose levels increase, which can seriously damage the body's organs.

Type 1 diabetes usually develops before the age of 40, often during the teenage years.

Type 1 diabetes is less common than type 2 diabetes. In the UK, it affects about 10% of all adults with diabetes.

If you're diagnosed with type 1 diabetes, you'll need insulin injections for the rest of your life.

You'll also need to pay close attention to certain aspects of your lifestyle and health to ensure your blood glucose levels stay balanced.

For example, you'll need to eat healthily, take regular exercise and carry out regular blood tests.

Read more about living with type 1 diabetes

Type 2 diabetes

Type 2 diabetes is where the body doesn't produce enough insulin, or the body's cells don't react to insulin. This is known as insulin resistance.

If you're diagnosed with type 2 diabetes, you may be able to control your symptoms simply by eating a healthy diet, exercising regularly, and monitoring your blood glucose levels.

However, as type 2 diabetes is a progressive condition, you may eventually need medication, usually in the form of tablets.

Type 2 diabetes is often associated with obesity. Obesity-related diabetes is sometimes referred to as maturity-onset diabetes because it's more common in older people.

Read more about living with type 2 diabetes

Diabetic eye screening

Everyone with diabetes aged 12 or over should be invited to have their eyes screened once a year by the national diabetes retinal screening service.

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.

Screening, which involves a half-hour check to examine the back of the eyes, is a way of detecting the condition early so it can be treated more effectively.

Read more about diabetic eye screening

Gestational diabetes (in pregnancy)

During pregnancy, all women need to make more insulin. In some women this doesn't happen and blood glucose levels rise - typically in the middle of pregnancy onwards.

Diabetes diagnosed in pregnancy is known as gestational diabetes.

Risk of gestational diabetes is increased with the same risk factors for type 2 diabetes (increased weight, at risk ethnicity and family history of diabetes), but also if you have given birth to a baby in the past who was bigger than expected.

For most women with gestational diabetes, blood glucose levels will return to normal after pregnancy. Although you will have an increased risk of developing diabetes in later life.

If you're worried about gestational diabetes then discuss this with your midwife.

Blood glucose control is also very important for women with diabetes before pregnancy (type 1, type 2 or other kinds). If you're planning a pregnancy or are in the early stages of pregnancy, it's important to discuss this with your GP, midwife or hospital clinic.

Other types of diabetes

In addition to Type 1, Type 2 and gestational diabetes, there are a range of other types of diabetes.

These types of diabetes are much rarer, with about 2% of people having them. The rare types of diabetes include:

  • different types of monogenic diabetes
  • cystic fibrosis-related diabetes
  • diabetes caused by rare syndromes
  • diabetes caused by certain medications such as steroids and antipsychotics
  • diabetes caused by surgery or hormonal imbalances

Unfortunately, many people with rarer types of diabetes are misdiagnosed leading to delays in getting the right treatment.

For more information on the other types of diabetes visit Diabetes UK and Diabetes Genes.

Last updated:
27 May 2021