Diabetes is a lifelong condition that causes a person's blood 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 3.9 million people living with diabetes in the UK. That's more than one in 16 people in the UK who has diabetes (diagnosed or undiagnosed).
This figure has more than doubled since 1996, when there were 1.4 million. By 2025, it is estimated that five million people will have diabetes in the UK.
Many more people have blood sugar levels above the normal range, but not high enough to be diagnosed as having diabetes.
This is sometimes known as prediabetes. If your blood sugar 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.
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.
The main symptoms of diabetes are:
Type 1 diabetes can develop quickly over weeks or even days.
Many people have type 2 diabetes for years without realising because the early symptoms tend to be general.
The amount of sugar 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.
In type 1 diabetes, the body's immune system attacks and destroys the cells that produce insulin. As no insulin is produced, your glucose levels increase, which can seriously damage the body's organs.
Type 1 diabetes is often known as insulin-dependent diabetes. It's also sometimes known as juvenile diabetes or early-onset diabetes because it 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 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.
You can use the BMI healthy weight calculator to check whether you're a healthy weight.
Read more about type 2 diabetes.
Everyone with diabetes aged 12 or over should be invited to have their eyes screened once a year.
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.
During pregnancy, some women have such high levels of blood glucose that their body is unable to produce enough insulin to absorb it all. This is known as gestational diabetes and affects up to 18 in 100 women during pregnancy.
Pregnancy can also make existing type 1 diabetes worse. Gestational diabetes can increase the risk of health problems developing in an unborn baby, so it's important to keep your blood glucose levels under control.
In most cases, gestational diabetes develops during the second trimester of pregnancy (weeks 14 to 26) and disappears after the baby is born.
However, women who have gestational diabetes are at an increased risk (30%) of developing type 2 diabetes later in life (compared with a 10% risk for the general population).
Read more about gestational diabetes.
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