Diabetes is a major public health concern across the developed world. In the UK, around 10% of the entire NHS budget is spent on diabetes, and the disease is amongst the top 10 causes of death worldwide. In diabetes, the body loses its ability to regulate blood sugar so that blood sugar levels are much higher than they should be. These high sugar levels result in widespread damage around the body, particularly to the kidneys, the eyes, the blood vessels, and the nerves. In all, diabetes is not good news.

Although some people have diabetes as a result of an autoimmune condition (Type 1 diabetes), most people with diabetes now suffer with Type 2 diabetes which is strongly related to diet and lifestyle. If your diet contains too much sugar, then your body is constantly producing insulin which is the hormone that lowers blood sugar levels. Because of the constant production of insulin, two things can happen; your body stops being able to produce enough insulin to meet the needs of your diet, or the cells of your body develop resistance to insulin and stop responding to it properly. Sometimes, both things can happen.

The changes that result in type 2 diabetes take time and there may be a lead in period of years before diabetes fully develops. This period, when blood sugar levels are higher than they should be but not high enough to diagnose diabetes, is the period of ‘pre-diabetes’ which is also known as impaired glucose tolerance. Usually, pre-diabetes causes no symptoms, but sometimes early signs of the damage caused by diabetes is evident even in the pre-diabetic stage.

The idea of pre-diabetes is a relatively new concept and reflects a more pro-active approach to the identification of those at risk of diabetes and a more pro-active approach to the prevention of diabetes. By identifying pre-diabetes, we gain the opportunity to act, the opportunity to reverse the trends of rising blood sugar that will eventually lead to diabetes. You are at higher risk of pre-diabetes (and diabetes) if you have a family history of Type 2 Diabetes, are overweight, have black, Hispanic or South Asian ancestry, or you have suffered with diabetes during pregnancy ('gestational diabetes'). 

We diagnose pre-diabetes with the same tests as those used to diagnose diabetes. These two tests are fasting blood glucose, and HbA1C (also known as glycated haemoglobin).

The fasting blood glucose test is taken in the morning after an overnight fast where you eat nothing, and drink only water, from about 10pm the night before the test. If your body is processing blood sugar properly then you blood sugar level should well within the normal range. A normal fasting blood sugar is between 3.9 and 5.4 mmol/l. A reading above 7.0 mmol/l is considered diagnostic of diabetes. The range between 5.5 and 6.9 mmol/l is the pre-diabetic range.

HbA1C is an interesting blood test. Whereas fasting blood glucose gives us a snapshot of your body’s ability to process sugar, HbA1C gives us a picture of how your body has been handling sugar over the last 3 months. The ‘Hb’ in HbA1C is haemoglobin which is iron containing molecule in red blood cells that transports oxygen around the body. Glucose attaches itself to the haemoglobin molecule (making the haemoglobin ‘glycated’), and the rate at which this happens depends on the amount of sugar in the blood.

Because red blood cells live for about 3 months, HbA1C tells us what the average blood sugar level has been over that period. It is a very useful test both for diagnosing pre-diabetes and diabetes, and for monitoring the conditions. An HbA1C below 42mmol/mol (sometimes given as 6%) is normal. An HbA1C of 48mmol/mol or above (sometimes given as 6.5%) suggests diabetes. The range between 42 and 47 mmol/mol is pre-diabetes.

Finding out that you have pre-diabetes should be seen as a positive thing. It gives you the chance to avoid a life impairing and life limiting disease. It should be taken as a spur to make lifestyle changes that will help prevent you from developing diabetes, but that will also reduce your risks of cardiovascular disease such as heart attacks and strokes.

Some doctors will advocate using medication in people with pre-diabetes (usually a tablet called metformin) but, more commonly, dietary changes are recommended. The primary aim of the diet is to reduce the amount of sugar that you eat and, if adhered to, diet changes have been shown to be just as effective as medication in preventing diabetes and have none of the potential side effects.

If you have developed pre-diabetes, then you will always remain at high risk of developing diabetes and it is generally recommended that you have your blood sugar levels checked at least annually. The lifestyle changes that you need to implement are therefore not a quick fix, but are really a lifelong commitment to keeping yourself healthy. But, if you maintain these changes after a diagnosis of pre-diabetes, then you will probably earn yourself a longer and healthier life.