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What is type 2 diabetes?


Key facts:
Type 2 diabetes is a long-term condition that can lead to serious health problems.
You can reduce the risk of problems by controlling your blood pressure, blood glucose levels and cholesterol.  Eating healthily, being physically active and not smoking are also important.

What is type 2 diabetes?  

Our 7-minute video provides an overview of what type 2 diabetes is and what happens inside the body.

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What is Type 2 Diabetes?

You can develop type 2 diabetes for two reasons:

  • your body can still make some insulin, but not enough to cope with glucose (sugar) in food
  • your body can still make some insulin but the insulin does not work properly (known as insulin resistance).

Type 2 is the most common form of diabetes (90 out of 100 people with diabetes worldwide have type 2 diabetes), and treatment can involve a combination of lifestyle changes, weight loss, tablets and injections.

You may sometimes hear type 2 diabetes called non-insulin dependent diabetes. This is an old term which isn't used much any more. It refers to the fact that not all people with type 2 diabetes will be treated with insulin, although some may need to be. 

What are the symptoms of type 2 diabetes?

The symptoms of diabetes may develop very slowly, and some people may not experience any symptoms at all. This means that people can live with type 2 diabetes for many years without realising they have it.

Symptoms of untreated type 2 diabetes include:

  • frequently needing to urinate
  • feeling thirsty
  • feeling tired
  • blurry vision
  • itchy skin, particularly around genitals
  • sudden weight loss.

See also above: Diagnosis | Glucose | Inside the body | The pancreas | Insulin


Diabetes is a group of conditions that have a number of features in common, including raised blood glucose levels (hyperglycaemia). There are different types of diabetes including type 1, type 2 and gestational diabetes.

If you have type 2 diabetes, your blood glucose levels can be raised for two reasons:

  • your pancreas is not producing enough insulin
  • the cells in your body are not responding properly to the insulin you are producing, a condition known as insulin resistance.

Either or both can happen in people with type 2 diabetes.

Blood glucose levels

1 2 1-glucose test

The World Health Organisation (WHO) state that the range of blood glucose levels that show you have diabetes are:

  • a fasting blood glucose level of 7.0 mmol/l or more—which means your blood glucose is 7 or more first thing in the morning after eating no food overnight, or
  • a blood glucose level of 11.1 mmol/l or more, two hours after taking a drink containing 75g of glucose.

There is another blood test called the HbA1c. This measures your average blood glucose levels in the past few months. HbA1c readings of more than 48 mmol/mol (6.5%) can be used to diagnose diabetes.

See also above: Overview | Glucose | Inside the body | The pancreas | Insulin


Key fact:
After exercise, muscles take glucose from the bloodstream: that's why taking exercise is so important for people with diabetes.

What is glucose?

Glucose is a form of sugar found in foods and is used as energy by the body. To release energy from glucose, the body needs the help of insulin.

Where does glucose come from?

Bread, potatoes, pasta, grains and other carbohydratesGlucose is a carbohydrate that comes from two main sources: the food you eat and your liver.

The glucose in food comes from sugars and complex carbohydrates like starch.

These are found in potatoes, bread, rice, yams, fufu, plantains and pasta. Your body joins glucose molecules together to make something called glycogen. Most of the glycogen in your body is stored in the liver and muscles.

yams and potatoesThe role of your liver

Your liver can also make glucose by breaking down its stores of glycogen.

It acts as a glucose bank and plays a very important role in controlling the level of glucose in the blood by storing any excess glucose as glycogen or converting it to fat.

Glycogen can be converted back into glucose by the liver when needed by the body, such as between meals and during physical activity.

How does the body use glucose?

Glucose is the main source of energy for all cells in the body.

Why is physical activity so important in looking after diabetes?

Because physical activity lowers blood glucose. 

Muscles have their own stores of glycogen. They can break this down into glucose when you are active. After exercising, muscles need to rebuild their stores of glycogen. They do this by taking glucose from the bloodstream.

This uptake of glycogen by the muscles after exercising lowers glucose levels in the blood. That is why physical activity is so important in helping people with diabetes.

See also above: Overview | Diagnosis | Inside the body | The pancreas | Insulin

Inside the body

Key fact:
In type 2 diabetes, glucose stays in the bloodstream instead of going into cells where it is needed. The body's attempts to deal with that imbalance eventually damage the pancreas.

What happens when someone without diabetes eats?

diagram showing how insulin and glucose work together in the body normallyWhen we eat, the carbohydrates in our food are digested by the body and broken down into glucose.

Glucose is absorbed by the body as a natural part of digestion and is carried around the body in the bloodstream.

When glucose is released into the bloodstream, our body detects that blood glucose levels have risen.

How your pancreas responds

Your pancreas responds to raised blood glucose levels by releasing insulin into the bloodstream. Insulin is a hormone that helps to release the energy from glucose.

When glucose and insulin reach the parts of the body that need energy, insulin should act like a key, unlocking the cells of the body to let glucose into the cell where it is used as energy.

When the cells use glucose as energy, blood glucose levels in the blood should drop.

What happens when someone with type 2 diabetes eats?

diagram showing how insulin and glucose work less effectively in the body of a person with type 2 diabetesIn people with type 2 diabetes, the body does not produce enough insulin, and the cells of the body do not react to insulin fully.

This means that when glucose and insulin in the bloodstream reach cells that need energy, insulin can’t unlock the cells properly. As a result, glucose remains in the bloodstream, causing blood glucose levels to rise.

More insulin is released

The pancreas responds to a high blood glucose level by releasing more insulin when the cells of the body are in need of energy (glucose).

Levels of glucose and insulin continue to rise to abnormal levels until the pancreas can’t cope any more and eventually wears out. The time it takes for the pancreas to wear out varies which means it's really important to make positive changes to your lifestyle as soon as you find out you have diabetes. 

See also above: Overview | Diagnosis | Glucose | The pancreas | Insulin

The pancreas

What is the pancreas?*

Your pancreas is a gland that helps your body in two important ways:

  • firstly, it makes digestive enzymes which are sent to the intestines to help the breakdown of food
  • secondly, it makes two hormones which regulate your blood glucose. These hormones are insulin, which lowers blood glucose, and Glucagon, which raises it.


Key definitions: hover over the words to see the definition


Why is the pancreas important in diabetes?

The pancreas is important beacuse it produces insulin and its job is to make sure that there is just the right amount of glucose in the body.

Parts of the pancreas, called islets of Langerhans, contain hormone-making cells. The islets of Langerhans also act as glucose sensors, releasing insulin when blood glucose levels rise above 4.4 mmol/l and releasing glucagon when blood glucose levels drop to below 4.4 mmol/l.

An individual islet is made up of several types of cell, each of which specialises in a particular hormone. One type, known as beta cells, can store a large amount of insulin and release it into the bloodstream when blood glucose levels rise.

See also above: Overview | Diagnosis | Glucose | Inside the body | Insulin


Key fact:
The body makes insulin to move glucose out of the blood and into the cells.
Fat deposits make this harder, so losing weight can help the insulin in your body work better.

What is insulin?

Insulin is a hormone made in the pancreas. Insulin helps glucose to release its energy into the cells of the body where it is needed. It also helps to control the amount of glucose in the blood.

Why is insulin important?

Insulin is a very important hormone as it helps to lower blood glucose levels. It does this in two main ways:

  • It tells the liver to stop making new glucose and start using up the glucose in the blood.
  • It encourages muscle and fat cells in your body to take glucose from the blood and turn it into glycogen and fat.

When insulin is released by the pancreas, it passes through the liver where it does several things:

  • stops the production of new glucose
  • increases the uptake of glucose
  • helps glucose to convert into glycogen and fat.

Insulin in the liver also increases the release of energy from glucose. It does this through chemical reactions that convert the glucose into carbon dioxide (CO2) and heat.

What is insulin resistance?

Insulin resistance occurs when the cells of the body don't respond as well to insulin. The insulin in the bloodstream doesn't work as well at unlocking the cells to the body which stops them being able to use glucose.

To deal with this the cells of the pancreas have to work much harder to produce more insulin. Over time this puts strain on the pancreas, and it stops working so well. This leads to diabetes.

By increasing your physical activity and losing weight you can reduce your insulin resistance.

See also above: Overview | Diagnosis | Glucose | Inside the body | The pancreas