Core concepts about diabetes

Diabetes is a common long-term health condition caused by too much glucose in the blood. It is also known as diabetes mellitus. In the UK, diabetes affects approximately 2.9 million people with an estimated 850,000 people who are unaware they have the condition.

Diabetes is a condition where the amount of glucose in a person’s blood is too high because their body is unable to process the glucose properly. This could be for two reasons:

  • the pancreas doesn’t produce any insulin, or not enough, to help glucose enter the cells of the body
  • the insulin that is produced does not work properly – this is known as insulin resistance.

Explore the animation below to follow the physiology of how the body manages glucose levels in the blood.

Glucose comes from digesting carbohydrate and is also produced by the liver.

Carbohydrate comes from many different kinds of foods and drinks. These include starchy foods such as bread, potatoes and chapattis; fruit; some dairy products; sugar and other sweet foods and drinks.

Insulin is the hormone produced by the pancreas that allows glucose to enter the body’s cells. Here the glucose is used as fuel, providing the body with energy for body function, movement and everyday living. Insulin is vital for life.

If a person has diabetes, their body cannot make proper use of glucose. The glucose builds up in their blood and they are unable to produce the energy needed for everyday life.

Diabetes is becoming an increasingly common long term condition in the UK. View the images below to see the prevalence of the two types of diabetes and the distribution of this condition across the UK.

Types of diabetes

Type 1 diabetes

Type 1 diabetes develops when the insulin-producing cells in the body have been destroyed and the body is unable to produce insulin. Type 1 diabetes is an autoimmune condition where the body attacks and destroys insulin-producing cells, meaning no insulin is produced. This causes glucose to quickly rise in the blood. No one knows why this happens but the most likely reason is that the body has an abnormal reaction to the cells. This could be triggered by an infection or virus but again this is not known for sure. Type 1 diabetes is often referred to as insulin-dependent diabetes. It can develop at any age but usually appears before the age of 40, and especially in childhood. A person with type 1 diabetes will need to take insulin injections for life. They will also need to ensure that their blood glucose level stays balanced by eating a healthy diet and carrying out regular blood tests. People with type 1 diabetes make up only 10% of all people with diabetes.

Type 2 diabetes

Type 2 diabetes develops when the body can still produce some insulin but not enough for it to function properly, or when the cells in the body do not react properly to insulin. This is called insulin resistance. The treatment of type 2 diabetes centres on lifestyle management including a healthy diet, regular exercise and the person monitoring their blood glucose level. As the condition progresses over time oral glucose therapies are also used, with or without additional insulin injections and Incretin mimetics / GLP-1 analogues. There are several oral agents for diabetes. Some help the body to use insulin more effectively whilst others increase the amount of insulin that the body produces.

Type 2 diabetes is often associated with obesity, and is also increasingly becoming more common in children, adolescents and young people of all ethnicities. Type 2 diabetes is far more common than type 1 diabetes - around 90% of all adults in the UK with diabetes have type 2 diabetes.

Type 2 diabetes risk factors include:

• Carrying too much excess body fat

• Having high blood pressure or cholesterol

• Genetic: having a close family member with type 2 diabetes

• Having previously had gestational diabetes

• Drugs such as steroids

• Ethnicity common in Asian and Afro-Caribbean, Age

(source Diabetes UK)

Explore the following interaction to learn more about different aspects of diabetes.


Pre-diabetes is a recognised condition and a growing problem across the globe. It is closely linked to obesity and is putting an increasing burden on the health care system.

If pre-diabetes is undiagnosed and untreated the patient will almost certainly develop into type 2 diabetes, which is treatable and can occasionally be reversed e.g gestational type 2. It is estimated that 7 million people in UK have pre-diabetes (Source: Many patients often don't know that they have it until it is too late as there are sometimes no noticeable symptoms.

Pre-diabetes occurs when blood glucose levels exceed normal levels but do not climb high enough to warrant a diagnosis of diabetes. It can be known as Impaired Glucose Tolerance (IGT) and Impaired Fasting Glycaemia (IFG).

Impaired Glucose tolerance

The patient's blood glucose level is raised beyond the normal range, but not to the diagnostic level of diabetes. Between 25% and 75% of people with IGT will develop diabetes within 10 years.

Impaired Fasting Glycaemia

The fasting blood glucose level is consistently elevated above what is considered normal, but not enough to be diagnosed as diabetes. It can progress into type 2 if lifestyle changes are not made. Information on the diagnostic ranges for IGT and IFG can be found in the Diagnosis and Screening section of this resource.

If your patient has pre-diabetes

If pre-diabetes is left untreated it will quickly develop into type 2 diabetes, usually in less than 10 years. A recent study showed that the average time that patients with IFG developed type 2 diabetes was less than 3 years (source: Progression From Newly Acquired Impaired Fasting Glucose to Type 2 Diabetes. Gregory A. Nichols, PHD1, Teresa A. Hillier, MD, MS1 and Jonathan B. Brown, PHD, MPP1).

A study by the Diabetes Prevention Program showed that patients with pre-diabetes can prevent it developing into type 2 diabetes, by making changes in their diet and increasing their physical activity. Working with your patient you can support them in their lifestyle change and encourage them to be involved in the management of their condition.

Patients with pre-diabetes symptoms still have the lifestyle choices to change their condition and early action can slow down or even stop the development of type 2 diabetes.

Diabetes in pregnancy (gestational diabetes)

Gestational diabetes is a type of diabetes that occurs during pregnancy (usually during the second or third trimester) and affects approximately 5% of pregnant women.

In some women, Gestational Diabetes Mellitus (GDM) occurs because the body cannot produce enough insulin to meet the extra needs of pregnancy. In other women, GDM may be found during the first trimester of pregnancy. In these women, the condition most likely existed before the pregnancy.

Gestational diabetes can increase the risk of health problems in an unborn baby, so it is important to keep the levels of blood glucose under control. Levels can often be controlled by diet but if not it may be necessary to prescribe tablets or insulin - usually in 10% – 20% of cases. The patient should be referred to a dietitian who will advise them about healthy eating.

Normalising blood glucose levels before planning a pregnancy is essential in reducing abnormalities to the foetus and to reduce the risk of a deterioration in pre-existing complications in either type 1 or type 2 diabetes. This is why all women with diabetes who are planning a pregnancy, need to be offered counselling and screening, to assess their individual risk and base line level of existing complications.

Children and diabetes

Most children with diabetes will be diagnosed with type 1. It is widely thought that this type of diabetes occurs in children because of their genetic makeup. However, with an increase in the number of children getting type 2 diabetes, it is generally acknowledged that diet, a lack of exercise, and deprivation are factors contributing to the rise in a population with a high genetic risk. There are approximately 31,500 people under the age of 17 with diabetes in England. Of these people 97% have type 1 diabetes, 1.5 % have type 2 and 1.5% are recorded as other. (Diabetes in the UK 2012.pdf). A decade ago type 2 diabetes was unheard of in children. With more children eating unhealthy diets and not taking enough exercise, they are becoming clinically obese and cases of type 2 diabetes have been increasing every year.

  • In 2000, the first cases of type 2 diabetes were diagnosed in overweight girls aged 9-16 years of Asian origin. It was first reported in 2002 for white adolescents.
  • Type 2 tends to cluster in families. If a family member is diagnosed then other family members are more likely to develop the condition.
  • In 2009/10 almost 1 in 4 children in England measured in reception year were overweight or obese. In year 6 the rate was 1 in 3. (source:

Diabetes today

Between 2006 and 2014 the number of people diagnosed with diabetes went from 1.9 million to 3.4 million. Every 3 minutes someone in the UK finds out that they have diabetes. (source: Diabetes UK). If growth of diabetes continues as it is then it is estimated that 6 million people in UK will have diabetes in 2025. It is already the single biggest cause of strokes, blindness, amputation and end stage kidney failure. Diabetes currently costs 10% of the NHS budget, that equated to £1 million per hour in 2011 (source: State of the Nation Most of the budget goes on managing complications that are avoidable. South Asian or Afro-Caribbean people are 6 times more likely to develop type 2 diabetes than any other ethnic groups, and are particularly at risk once they are over the age of 25.

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