What is Diabetes? | Viva!

What is Diabetes?

What is Diabetes?

Diabetes mellitus (the full medical name) is a health condition characterised by high levels of glucose (sugar) in the blood, which the body cannot use properly and eventually excretes in the urine, together with a lot of water. It is caused either by the pancreas not producing the hormone insulin - or not enough of it - or by the body cells' inability to react to insulin.

Insulin is produced by the pancreas and acts as a key that lets glucose into the body's cells. Glucose is a sugar that is a vital source of energy for all cells and thus the main fuel for the body's processes. It comes from digesting carbohydrates and it's also partially produced by the liver. Carbohydrates are the main nutrient in healthy foods such as wholegrain or rye bread, pasta, oats, brown rice, pulses (beans, peas and lentils), sweet potatoes, and in not so healthy foods such as white bread, cakes, sweets and other sugary foods.

If the body cannot use glucose as a source of energy, it uses fat instead but this inevitably disturbs the biochemical balance of the body and leads to further health complications. Typical examples of this are unhealthy diets such as the Atkins, where carbohydrates are avoided in favour of fatty foods. Symptoms of diabetes include tiredness, irritability, nausea, hunger, thirst, weight loss, blurred vision, tingling sensations in the hands and feet and dry, itchy skin.

In 1985, an estimated 30 million people worldwide had diabetes; a decade later this figure had increased to 135 million and by 2000 an estimated 171 million people had diabetes. It is predicted that at least 366 million people will have diabetes by 2030. This rapid increase is attributed to a range of factors, including population growth, ageing, unhealthy diets that are high in saturated fat and cholesterol, obesity and lack of physical exercise.

In the UK alone, 2.8 million people have been diagnosed with diabetes but it is estimated that up to half a million more have the disease but have not yet been diagnosed. Just in 2008, 145,000 people were diagnosed with diabetes in the UK - that's around 400 people every day! According to the latest numbers, it is expected that by 2025 over four million people will have it. Because of a rapid increase in the number of overweight and obese people, and because the population is ageing, most of these cases will be type 2 diabetes.

Diagnosing diabetes

A diagnosis is arrived at after repeated blood tests which measure the amount of glucose (sugar) in the blood, specifically in the part of the blood called plasma. You will be diagnosed with diabetes if your tests show that:

  • plasma glucose after fasting for 8-12 hours is more than 7.0mmol/l (126mg/dl)and/or
  • plasma glucose two hours after ingesting a special glucose drink is more than 11.1mmol/l (200mg/dl)

Another criterion is called glycosylated haemoglobin (HbA1c) which reflects the average level of blood glucose over a period of weeks. Haemoglobin molecules are one of the main components of red blood cells and when glucose binds to haemoglobin in the bloodstream HbA1c occurs. The more glucose there is, the more HbA1c will be present. Red blood cells survive for eight to 12 weeks before renewal and so by measuring HbA1c, an average blood glucose reading can be established.

For non-diabetics, the usual reading is 3.5- 5.5 per cent. For people with diabetes, an HbA1c level of 6.5 per cent is considered good control, although the closer to the nondiabetic figure, the better.

Type 1 diabetes

Type 1 diabetes usually develops early in life when the immune system attacks the insulinproducing cells in the pancreas and effectively destroys them. The body is then unable to produce any insulin. Because insulin is the key which allows glucose to enter the body's cells, when it is absent the glucose goes unused and builds up in the blood.

Type 1 diabetes accounts for approximately 10 per cent of all people with diabetes but is increasing rapidly in all age groups, with a particularly steep rise amongst children under five years old.

The evidence is growing that a combination of susceptible genes and early exposure to cows' milk is responsible for this self-harming reaction of the body. A virus or other infection may also be implicated in triggering the condition.


HbA1c & Glucose Blood Levels
HbA1c (%) Avg. Blood Glucose (mmol/l) Stage of diabetes
Levels of HbA1c above 6.5% are considered diabetic
6 7 HbA1c 6 - 6.5% is considered pre-diabetes or at risk of diabetes
5 5 HbA1c 3.5 - 5.5% is considered normal


Type 2 diabetes

In type 2 diabetes, the body can still make some insulin but not enough, or it doesn't react to insulin properly (insulin resistance) so, again, glucose builds up in the blood. Approximately 90 per cent of all people with diabetes in the UK have type 2.

It usually develops in people over the age of 40, but South Asian and African-Caribbean people are at greater risk as they often become diabetic relatively early in life - around the age of 25. The disease is rapidly becoming more common in children, adolescents and young people of all ethnicities as it is closely linked to the rapid increase in childhood obesity.

Metabolic syndrome

Metabolic syndrome, or Syndrome X, is characterised by central obesity (weight accumulated mostly around the waist), raised blood pressure, raised triglycerides (fats in the blood), low HDL (the 'good' cholesterol that is being cleared from the bloodstream) and impaired glucose metabolism. Impaired glucose metabolism means that the body is not using glucose properly and the level in the blood is raised but has not yet reached diabetic levels.

All these symptoms significantly increase the risk of diabetes and cardiovascular (heart) disease.


Those with impaired glucose metabolism are diagnosed with pre-diabetes - a condition associated with insulin resistance. The main cause is obesity and related risk factors include high blood pressure, low HDL cholesterol, and high triglycerides.

Pre-diabetes almost always precedes type 2 diabetes but many people don't know they have it until diabetes develops. However, both pre-diabetes and metabolic syndrome are reversible with the right approach.

It's not all sweet

Diabetes is not usually diagnosed immediately after it starts and so by the time the diagnosis is made, many people will have already developed other health complications resulting from diabetes. Even those who are aware of their diabetic condition and have adjusted their lifestyle, are still at considerable risk of heart disease, stroke, eye problems, kidney disease, nerve damage and amputations.