Prediabetes is a metabolic condition in which blood glucose levels are higher than normal, but not yet high enough to be classified as type 2 diabetes. It is estimated that around five million people in the UK currently have prediabetes — and the majority are unaware of it. This matters enormously, because prediabetes is both a warning signal and, crucially, a window of opportunity. With the right lifestyle changes, the progression to type 2 diabetes can be prevented or significantly delayed.
What Are the Blood Sugar Levels for Prediabetes?
Prediabetes is diagnosed using one of two blood tests. The first is fasting plasma glucose, taken after at least eight hours without food. A result of 6.1 to 6.9 mmol/L is classified as impaired fasting glucose (IFG), which is one form of prediabetes.
The second test is HbA1c — a measure of average blood glucose over the past two to three months. An HbA1c of 42 to 47 mmol/mol (6.0% to 6.4%) indicates prediabetes according to the NHS and Diabetes UK.
A third test, the oral glucose tolerance test (OGTT), measures glucose two hours after drinking a standardised glucose solution. A result of 7.8 to 11.0 mmol/L at the two-hour mark indicates impaired glucose tolerance (IGT) — another form of prediabetes.
Having IFG, IGT, or a raised HbA1c does not mean you will develop type 2 diabetes. But without intervention, the risk is significantly elevated — approximately 5 to 10 percent of people with prediabetes progress to type 2 diabetes each year.
Signs and Symptoms
One of the most challenging aspects of prediabetes is that it typically causes no obvious symptoms. Unlike full type 2 diabetes — which may produce increased thirst, frequent urination, fatigue, and blurred vision — prediabetes is often entirely silent. This is why routine screening is so important.
Some people may experience subtle signs such as persistent fatigue, difficulty losing weight despite reasonable dietary effort, skin darkening in body creases (a condition called acanthosis nigricans, linked to insulin resistance), or unusually intense sugar cravings. However, these are non-specific and cannot be relied upon for diagnosis. A blood test is the only reliable way to know.
Risk Factors for Prediabetes
Several factors increase your likelihood of developing prediabetes. According to Diabetes UK and NHS guidance, the main risk factors include being over the age of 40 (or over 25 for South Asian, Chinese, African, Caribbean, or Black African heritage), having a BMI above 25 kg/m², having a close family member (parent or sibling) with type 2 diabetes, having had gestational diabetes during pregnancy, having polycystic ovary syndrome (PCOS), having a history of cardiovascular disease, and being physically inactive.
The Diabetes UK Know Your Risk tool is a free online calculator that estimates your risk based on these factors. If you are over 40 and have not had a blood glucose test in the past year, it is worth asking your GP for one — or checking whether you are eligible for the NHS Health Check (available to all adults aged 40 to 74 in England every five years).
Can Prediabetes Be Reversed?
Yes — and the evidence is robust. The landmark US Diabetes Prevention Program (DPP), which followed over 3,000 participants with prediabetes for nearly three years, found that intensive lifestyle intervention — moderate weight loss of 5 to 7 percent of body weight, combined with 150 minutes of moderate-intensity physical activity per week — reduced progression to type 2 diabetes by 58 percent.
In the UK, the NHS Diabetes Prevention Programme (NDPP) offers a free, structured programme for people identified with prediabetes in England. Participants receive personalised coaching on diet, physical activity, and behaviour change. Research on the UK programme shows meaningful reductions in HbA1c and body weight.
Even without a formal programme, the key principles are clear: achieving and maintaining a healthy weight (even a 5 to 10 percent reduction in body weight makes a significant difference), increasing physical activity to at least 150 minutes of moderate exercise per week, reducing consumption of ultra-processed foods and refined carbohydrates, and increasing dietary fibre.
Key Takeaways
Prediabetes is not a foregone conclusion — it is a fork in the road. The body is still responding to lifestyle changes at this stage in a way it may not once type 2 diabetes is established. If you have been told your blood glucose or HbA1c is in the prediabetes range, take it seriously and act on it — but also take heart that there is a great deal within your power to change the outcome.