By ALICE SMELLIE

Last updated at 08:39 19 March 2008

Over 60,000 Britons are unaware they have diabetes

Feeling permanently tired is the story of many people's lives.

While most of us put it down to our busy lifestyles, for thousands of Britons chronic tiredness is actually a sign of something far more worrying: diabetes.

Over 60,000 Britons have the condition yet don't know it, according to a study published earlier this month.

A further 500,000 are thought to be "borderline" cases, at risk of developing diabetes.

With advice on healthy eating and exercise, these half-a-million people could be prevented from developing the disease - if they knew they were at risk.

Once it develops, diabetes is still controllable if properly treated. But living with undiagnosed diabetes is extremely dangerous.

As the study's lead researcher, Dr Tim Holt, from Warwick University, explained: "It's important that we find patients with diabetes so they can be treated and to prevent the heart problems they are prone to."

"Diabetes is not a condition to be taken lightly," adds Dr Laurence Gerlis, Medical Advisor to the Insulin Dependent Diabetes Trust.

"Every year, 5,000 diabetics have a limb amputation due to nerve damage - that's 100 people a week."

Other long-term complications can include blindness and kidney disease.

Experts agree that the earlier people are diagnosed, the earlier they can get on with managing the condition and reduce the risk of these complications.

The problem is that many patients with undiagnosed diabetes don't have the classic symptoms associated with the disease, such as constant thirst and an increased need to urinate.

In fact, many have no symptoms at all. "Even someone who looks perfectly well, not overweight at all, can be affected," says Dr Gerlis.

Most of the 2.3 million Britons diagnosed with the disease have Type 2 diabetes.

In Type 1, the body is unable to produce insulin, the hormone that helps control sugar levels in the blood.

With Type 2, the body still produces insulin, but not enough, or else the insulin it does produce doesn't work properly, leading to high blood sugar levels.

(Those with glucose intolerance, the precursor to Type 2 diabetes, have high blood sugars, but not high enough to be deemed diabetic).

Even when symptoms are apparent, many people will probably put them down to a hectic lifestyle, says Cathy Moulton, care adviser at Diabetes UK.

"This is why it's so often ignored and why so many fail to recognise just how much danger they could be in."

No one knows for sure why people develop diabetes, but it is known to be linked to weight and lifestyle factors - particularly lack of exercise.

A high Body Mass Index (BMI) can be a risk factor. Your BMI determines whether you are a healthy weight - if it's over 25, you are overweight and could be at risk.

There is also a genetic link, and certain ethnic groups - people of Afro-Caribbean and Asian descent - are at much higher risk.

"It is absolutely imperative that people don't ignore symptoms - especially as addressing the problem is so simple," says Ms Moulton.

"If you have any doubts, go to see your GP."

The good news, says Dr Gerlis, is that once diagnosed, glucose intolerance is manageable and possibly reversible, and can be prevented from becoming full-blown diabetes by moderating lifestyle.

"Equally, if caught early, treatment for Type 2 diabetes can be as straightforward as making simple lifestyle adjustments - a healthy diet, weight loss and increased physical activity. The important thing is to have a test to rule out either condition," he says.

"In the same way everyone should know their blood pressure and cholesterol, everyone should be aware of their blood sugar levels - using either a home testing kit or going to their GP."

To see just how common undiagnosed diabetes is, we asked ten men and women aged between 35 and 50 (diabetes usually develops after the age of 40) to take a glucose test.

They used an over-the-counter home kit from Boots - the Blood Glucose Home Test Kit, £11.99. The test involved a sample of blood taken via a pin prick, put on the test paper and placed in the monitor.

A reading appeared on screen within seconds.

Anyone with levels of blood sugar greater than 5.9 mmol/l (millimoles per litre of blood) if they hadn't eaten - and 8.9 mmol/l if they had - was sent to a GP for further blood tests and a urine test to check for high sugar levels, another sign of diabetes.

If results were still unclear, an overnight glucose tolerance test was suggested, to measure how quickly glucose cleared from the blood.

The results were eye-opening.