Prediabetes: The Warning Sign for Type 2 Diabetes That's Often Missed
By Dr Daniel Gordon • 2, Oct 2026
Prediabetes affects more than 1 in 3 adults in the UK, and most do not know they have it. Unlike type 2 diabetes, prediabetes rarely causes noticeable symptoms.
That is exactly what makes it dangerous. Left unmanaged, it can progress to type 2 diabetes within five years. Caught early, it can often be reversed entirely.
Here is what prediabetes actually is, why it happens, and what the evidence says about turning it around.
What Is Prediabetes?
Prediabetes means blood sugar levels are higher than normal, but not yet high enough to be classed as type 2 diabetes.
It is sometimes described as a "warning stage." The body is starting to struggle with insulin, the hormone that moves sugar out of the bloodstream and into cells for energy. When insulin stops working as efficiently as it should, sugar builds up in the blood instead.
Prediabetes is usually diagnosed using one of these tests:
HbA1c test: measures average blood sugar over the past two to three months. A result of 42–47 mmol/mol (6.0–6.4%) indicates prediabetes.
Fasting plasma glucose test: measures blood sugar after not eating for at least eight hours. A result of 5.5–6.9 mmol/L falls in the prediabetes range.
Oral glucose tolerance test: measures blood sugar before and two hours after drinking a sugary liquid. A two-hour result of 7.8–11.0 mmol/L indicates prediabetes.
Who Is at Risk?
Prediabetes does not have a single cause. It develops from a combination of factors, some changeable and some not.
Risk factors that cannot be changed:
Being over 45 (though it increasingly affects younger adults)
A parent or sibling with type 2 diabetes
A history of gestational diabetes
Being of South Asian, Black African, or African-Caribbean descent, which carries a higher risk at a lower BMI
Risk factors that can be changed:
Carrying excess weight, particularly around the abdomen
Low physical activity levels
High blood pressure or abnormal cholesterol
Poor sleep quality or chronic sleep deprivation
Smoking
Does Prediabetes Have Symptoms?
Usually not. This is the central problem with prediabetes: it is largely silent. Some people notice subtle signs, but many have none at all.
Symptoms, when they do appear, may include:
Increased thirst
Frequent urination
Fatigue
Blurred vision
Darkened patches of skin, often at the neck or armpits (a sign called acanthosis nigricans)
Because symptoms are unreliable, screening matters more than waiting for warning signs. Anyone with two or more risk factors above should ask their GP about a blood sugar test, even if they feel completely well.
Can Prediabetes Be Reversed?
Yes, and this is backed by some of the strongest evidence in preventive medicine.
The landmark Diabetes Prevention Program (DPP), a US clinical trial involving over 3,000 participants, found that structured lifestyle changes reduced the risk of progressing to type 2 diabetes by 58% over three years, outperforming metformin, a commonly prescribed medication, which reduced risk by 31%. Among adults over 60, lifestyle intervention was even more effective, cutting risk by 71%.
The changes that produced these results were not extreme. Participants aimed for:
5–7% body weight loss (roughly 10–14 lbs for someone weighing 200 lbs)
150 minutes of moderate activity per week (brisk walking counts)
Modest, sustainable changes to diet rather than short-term restriction
What Helps, Based on the Evidence
Movement:
Aim for at least 150 minutes of moderate-intensity activity weekly
Break up long periods of sitting — even short walks help insulin sensitivity
Strength training two to three times a week supports long-term blood sugar control
Diet:
Prioritise fibre — vegetables, legumes, and whole grains slow sugar absorption
Limit refined carbohydrates and sugary drinks, which cause rapid blood sugar spikes
Focus on consistent meal timing rather than skipping meals
The strongest evidence supports a combination of regular activity, an eating pattern that improves diet quality, and, where appropriate, sustained weight loss. Small, repeatable changes tend to outperform an extreme plan that only lasts a week.
1. Move More, and Include Strength Work
Working muscles take up glucose, and regular activity improves insulin sensitivity, sometimes before there is much change in weight. The general UK target is at least 150 minutes of moderate activity each week, plus muscle-strengthening activity on at least two days.
A realistic starting plan might include:
A 10- to 15-minute brisk walk after one or two meals
Breaking up long periods of sitting every 30 to 60 minutes
Two short strength sessions each week using weights, resistance bands, or suitable bodyweight exercises
Increasing time or intensity gradually
Joint pain, heart symptoms, foot problems, or diabetes complications may require an adapted plan. Anyone using insulin or medication that can cause hypoglycaemia should ask their diabetes team how to exercise safely.
2. Improve Carbohydrate Quality and Portion Size
Carbohydrate is broken down into glucose, but carbohydrate-rich foods are not nutritionally identical. Fibre content, portion size, and the overall meal all affect the glucose response.
Useful changes include:
Replacing sugary drinks with water or unsweetened alternatives
Choosing higher-fibre foods such as oats, wholegrain bread, beans, and lentils
Including vegetables and a source of protein with main meals
Replacing some saturated fat with nuts, seeds, olive oil, and fish
Reducing frequent pastries, biscuits, processed meat, and large portions of refined carbohydrates
There is no single ideal diet for everyone. Mediterranean-style, lower-carbohydrate, and structured portion-based approaches can all be reasonable. The best choice is one that fits a person's culture, preferences, budget, and medical needs.
Anyone taking glucose-lowering medication should speak to their diabetes team before fasting, starting a very-low-calorie diet, or substantially reducing carbohydrate, as medication doses may need to change. Very-low-carbohydrate diets require particular caution alongside certain medications, for example SGLT2 inhibitors like dapagliflozin and empagliflozin.
3. Aim for Weight Loss, Where Appropriate
Not everyone with prediabetes needs to lose weight. For people living with overweight or obesity, however, sustained weight loss can improve insulin sensitivity and reduce the demand on the pancreas.
A loss of around 5% to 7% of starting weight can be clinically meaningful. Preserving muscle through adequate nutrition and resistance exercise is important, particularly in midlife and later life.
Other factors:
Sleep: 7 to 9 hours a night; poor sleep is independently linked to insulin resistance
Smoking: stopping smoking improves insulin sensitivity over time
Stress: ongoing high stress raises cortisol, which can raise blood sugar
What About Medication?
Lifestyle change is the first-line approach, but it is not the only tool available. In some cases, a healthcare provider may also recommend:
Metformin: the most established medication option, particularly for those under 60, with a BMI of 35 or above, or with a history of gestational diabetes
GLP-1 agonists - For example Semaglutide (Ozempic, Wegovy), and Tirzepatide (Mounjaro): a newer class of medication, originally developed for type 2 diabetes, that supports both blood sugar control and weight loss. They are increasingly used off-label for prediabetes in people who also carry excess weight, though they are not yet routinely prescribed for prediabetes alone on the NHS
Referral to a structured prevention programme, where available, combining supervised lifestyle support with regular monitoring
When to See a Healthcare Provider
Anyone with risk factors, or a family history of type 2 diabetes, should not wait for symptoms before requesting a blood sugar test. Progression from prediabetes to type 2 diabetes is not inevitable, but it becomes more likely without a plan in place. The options above are far more effective when started early rather than after a type 2 diabetes diagnosis.
The Bottom Line
Prediabetes is common, often silent, and frequently reversible. The evidence is clear that modest, sustained changes, not drastic ones, produce meaningful results. The earlier it is identified, the more options there are for turning it around.
Disclaimer
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