Type 2 diabetes occurs when the pancreas doesn't produce enough insulin to maintain a normal blood glucose level, or the body is unable to use the insulin that is produced (insulin resistance).
The pancreas is a large gland behind the stomach that produces the hormone insulin. Insulin moves glucose from your blood into your cells, where it's converted into energy.
In type 2 diabetes, there are several reasons why the pancreas doesn't produce enough insulin.
Risk factors for type 2 diabetes
Three of the main risk factors for developing type 2 diabetes are:
- age – being over the age of 40 (over 25 for people of south Asian, Chinese, African-Caribbean or black African origin, even if you were born in the UK)
- genetics – having a close relative with the condition, such as a parent, brother or sister
- weight – being overweight or obese
People of south Asian and African-Caribbean origin also have an increased risk of developing complications of diabetes, such as heart disease, at a younger age than the rest of the population.
These risk factors are discussed in more detail below.
Read about reducing your risk of type 2 diabetes.
Your risk of developing type 2 diabetes increases with age. This may be because people tend to gain weight and exercise less as they get older.
Maintaining a healthy weight by eating a healthy, balanced diet and exercising regularly are ways of preventing and managing diabetes.
White people over the age of 40 have an increased risk of developing the condition. People of south Asian, Chinese, African-Caribbean and black African origin have an increased risk of developing type 2 diabetes at a much earlier age.
However, despite increasing age being a risk factor for type 2 diabetes, over recent years younger people from all ethnic groups have been developing the condition.
It's also becoming more common for children – as young as seven in some cases – to develop type 2 diabetes.
Genetics is one of the main risk factors for type 2 diabetes. Your risk of developing the condition is increased if you have a close relative such as a parent, brother or sister who has the condition.
The closer the relative, the greater the risk. A child who has a parent with type 2 diabetes has about a one in three chance of also developing the condition.
Being overweight or obese
You're more likely to develop type 2 diabetes if you're overweight or obese.
For most people in the UK, a body mass index (BMI) of:
- 25 or above puts you in the overweight range
- 30 or above puts you in the obese range
However, some groups have a higher risk of developing type 2 diabetes:
- Asians with a BMI score of 23 or more are at increased risk of developing type 2 diabetes
- Asians with a BMI of 27.5 or more are at high risk of developing type 2 diabetes
Fat around your tummy (abdomen) particularly increases your risk. This is because it releases chemicals that can upset the body's cardiovascular and metabolic systems.
This increases your risk of developing a number of serious conditions, including:
Measuring your waist is a quick way of assessing your diabetes risk. This is a measure of abdominal obesity, which is a particularly high-risk form of obesity.
Some groups have a higher risk of developing type 2 diabetes, based on their waist measurements:
- women with a waist size of 80cm (31.5 inches) or more
- Asian men with a waist size of 89cm (35 inches) or more
- white or black men with a waist size of 94cm (37 inches) or more
Use the BMI calculator to find out if you're a healthy weight for your height.
Exercising regularly and reducing your body weight by about 5% could reduce your risk of getting diabetes by more than 50%.
Read information and advice about losing weight.
Your risk of developing type 2 diabetes is also increased if your blood glucose level is higher than normal, but not yet high enough to be diagnosed with diabetes.
This is sometimes called pre-diabetes, and doctors sometimes call it impaired fasting glycaemia (IFG) or impaired glucose tolerance (IGT).
Pre-diabetes can progress to type 2 diabetes if you don't take preventative steps, such as making lifestyle changes. These include eating healthily, losing weight if you're overweight, and taking plenty of regular exercise.
Women who have had gestational diabetes during pregnancy also have a greater risk of developing diabetes in later life.