Prediabetes

This page provides general information about diet-related ill-health. For individual advice always seek guidance from a qualified health professional.

What is prediabetes?

Prediabetes occurs when blood sugar (glucose) levels are higher than they should be, but not high enough to diagnose type 2 diabetes. It’s an early warning sign there’s an increased risk of developing the condition.

Being diagnosed with prediabetes doesn’t automatically mean a person will develop type 2 diabetes. For many people, making lifestyle changes – such as eating more healthily, being more active and losing weight if needed – can successfully lower blood sugar levels to within the healthy range and potentially prevent the onset of type 2 diabetes.

Key facts

Prediabetes is a warning sign a person is at high risk of developing type 2 diabetes
Prediabetes affects around 1 in 9 adults in England (12%) – that’s equal to around 5.1 million adults
Prediabetes is sometimes called borderline diabetes or non-diabetic hyperglycaemia
Making lifestyle changes may prevent or delay up to 50% of cases of type 2 diabetes

What causes prediabetes?

Prediabetes is caused by problems with insulin. This hormone is made in the pancreas and helps to move sugar (glucose) from the blood into cells where it provides energy. When insulin functions properly, blood sugar levels are well controlled and stay within a healthy range.

If the pancreas fails to make enough insulin, or if the insulin produced isn’t effective, then less sugar is removed from the blood. This condition is called insulin resistance. It means sugar starts to build up in the blood causing blood sugar levels to rise.

Prediabetes is diagnosed when blood sugar levels are slightly higher than normal indicating early problems with insulin function. Over time, if insulin resistance worsens and blood sugar levels continue to rise, this can lead to type 2 diabetes.

What are the symptoms of prediabetes?

Unlike type 2 diabetes, which has several noticeable symptoms, prediabetes doesn’t usually have any warning signs, making it difficult to know whether you have the condition. If symptoms are present, this means you may already have developed type 2 diabetes. Common symptoms of undiagnosed or uncontrolled type 2 diabetes include…

Feeling very tired
Feeling very thirsty
Peeing more often, especially at night
Blurred vision
Itchy genitals
Frequent episodes of thrush
Cuts that take longer to heal

If you develop any of the above symptoms, make an appointment with your GP so a diagnosis can be made, the condition can be monitored and, if necessary, treatment can begin to lower and stabilise blood sugar levels.

How will I know if I have prediabetes?

As prediabetes has no obvious symptoms, it can be difficult to know if you have the condition. Understanding the main risk factors for prediabetes and type 2 diabetes means you will be able to identify if any apply to you (see the table below). The more risk factors you have, the higher the chances of developing prediabetes or type 2 diabetes.

You can also complete the Know Your Risk online tool developed by Diabetes UK. It takes just a few minutes and will indicate whether you have a high or very high risk of developing type 2 diabetes. If the results show you are at risk, you should make an appointment with your GP.

It's also common for prediabetes or type 2 diabetes to be diagnosed through blood tests completed for other medical conditions or through the free NHS Health Check, available to people aged 40 and 74 years in England.

You can also ask your GP practice to check for prediabetes if you think you might be at risk.

A blood test that measures blood sugar (glucose) levels is the only way to confirm a diagnosis of prediabetes. Several tests can be used but a common one checks HbA1c levels in the blood. This test provides an average of your blood sugar levels over the past two to three months. A reading between 42-47mmol/mol is a sign of prediabetes. A level of 48mml/mol or more indicates type 2 diabetes.

What are the risk factors for prediabetes?

Both prediabetes and type 2 diabetes are due to problems with insulin function. As they have the same underlying cause, they also share similar risk factors.

Some of these risk factors such as age, ethnicity and family history can’t be changed. But it’s often possible to lower the risk of developing prediabetes and type 2 diabetes by making lifestyle changes such as eating a healthier diet, being more physically active, and losing weight if needed.

The following chart shows the main risk factors for prediabetes and type 2 diabetes…

Risk Factor	Explanation
Your weight…	The more overweight you are the greater your risk. To find out if you are living with overweight or obesity ask your GP to measure your BMI (body mass index) – a healthy BMI is 18.5-25
Your waist…	Women – if your waist measures 80cm or more you have an increased risk of developing prediabetes or type 2 diabetes; the risk is very high if it is more than 88cm. Men – if your waist measures 94cm or more you have an increased risk of developing prediabetes or type 2 diabetes. If you are male with South Asian background the measurement is 90cm or more; the risk is very high if it is more than 102cm.
Your age…	You are at increased risk of prediabetes or type 2 diabetes if you are over 40 years of age. If your background is Black African, Chinese, South Asian or African-Caribbean, you are at increased risk if you are over 25 years of age. The risk continues to increase with age.
Your family history…	Having type 2 diabetes in the family increases your risk. The closer the relative is, the greater the risk. Tell your GP whether anyone in your family has type 2 diabetes. If you know that type 2 diabetes runs in your family, make sure that you are doing all you can to reduce your risk in other ways.
Your ethnicity…	Some ethnic groups have higher risk of type 2 diabetes than others and are likely to be affected at an earlier age (see ‘Your age’ section above). If you have an African-Caribbean or South Asian background and live in the UK, then you are at least three times more likely to have type 2 diabetes than the White population. It is particularly important for you to make sure that you maintain a healthy body weight.
Lifestyle factors…	Several lifestyle factors, some of which are linked to living with overweight and obesity, have been associated with an increased risk of developing type 2 diabetes. These include smoking, being sedentary and eating an unhealthy diet.
Other factors...	You may also have an increased risk of having prediabetes or type 2 diabetes if you: Have high blood pressure or if you’ve had a heart attack or a stroke Are a woman with a history of polycystic ovary syndrome, gestational diabetes (a temporary type of diabetes during pregnancy) or have given birth to a large baby Have been told you have impaired glucose tolerance or metabolic syndrome.

Being diagnosed with prediabetes doesn’t automatically mean a person will develop type 2 diabetes. Making lifestyle changes – such as eating more healthily, being more active and losing weight if needed – can successfully lower blood sugar levels to within the healthy range and potentially prevent the onset of type 2 diabetes.

Sara Stanner, Science Director

How to lower the risk of type 2 diabetes

Being diagnosed with prediabetes means a person has an increased risk of developing type 2 diabetes, but it doesn’t mean they will definitely get the condition. The key to preventing prediabetes from progressing to type 2 diabetes for many people is making important lifestyle changes.

Research shows that adopting a healthy diet, being more physically active, and losing weight, if needed, reduces the risk of developing type 2 diabetes by around 50%. Better still, these lifestyle modifications may prevent or delay the onset of type 2 diabetes for many years. Trials have reported a lower incidence of type 2 diabetes up to 23 years after making lifestyle changes.

If you live in England and are diagnosed with prediabetes, your GP may refer you to the NHS Diabetes Prevention Programme. This nine-month programme helps people at high risk of developing type 2 diabetes make lasting lifestyle changes to prevent the condition.

Eat a healthy, balanced diet

Eating a healthy diet is key to lowering the risk of type 2 diabetes. A good starting point is to follow The Eatwell Guide, which shows the types and proportions of foods to eat for a balanced, nutritious and sustainable diet.

Both high fat and low fibre diets have been found to increase the risk of developing type 2 diabetes. This means it’s important to make diet changes that reduce fat and increase fibre.

Ways to reduce fat
Ways to increase fibre

Certain eating patterns such as the Mediterranean Diet and the DASH diet (Dietary Approaches to Stop Hypertension) have also been shown to lower the risk of type 2 diabetes by around a fifth. These diets promote vegetables, fruit, wholegrains, pulses, nuts and seeds. They include some low-fat dairy products and lean protein-rich foods such as fish, poultry and eggs, but limit red meat, butter, sugar, and processed foods.

Vegetarian and vegan diets have also been shown to reduce the risk.

The common theme with all these diets is their alignment with UK healthy eating recommendations: they’re rich in plant-based foods, contain moderate amounts of animal products, and are low in sugary, fatty and processed foods.

6 diet tips to protect against type 2 diabetes

1. Eat fewer sugary foods

Sugar itself doesn’t directly cause type 2 diabetes, but it is linked to higher energy (calorie) intakes. Over time, taking in more calories than we need can cause weight gain, which increases the risk of type 2 diabetes. A good starting point is to swap chocolate, cake, biscuits, sweet pastries, ice cream and desserts, for fruit.

2. Limit sugary drinks

Higher intakes of sugar-containing drinks are linked to a higher risk of type 2 diabetes. Studies also show they’re associated with weight gain and a higher Body Mass Index (BMI) in children and teens. Replace sugary drinks with water and sugar-free drinks. Some studies suggest that coffee and tea may also lower the risk of type 2 diabetes but, if you drinks these, have them without sugar.

3. Eat more vegetables and fruits

Eating more vegetables and fruit is linked to a decreased risk of type 2 diabetes. The key thing is to eat more and to have a variety of different kinds. Frozen, canned and dried varieties still count towards your 5 A DAY - try to include vegetables or fruit (or both!) at each meal and as snacks to help you get at least 5 A DAY.

4. Choose high-fibre carbs

There’s no evidence the total amount of carbohydrate in a diet increases the chances of developing type 2 diabetes, but studies do show some carbohydrate-rich foods may affect risk. Good amounts of wholegrains, such as wholemeal bread, brown pasta and rice, oats, and wholegrain breakfast cereals, lower the risk so it’s important to include these in our daily diet. In contrast, there is some evidence (although limited) that suggests that high intakes of white rice and potatoes, especially if fried, could be linked to an increased risk. So it's best to replace more refined carbohydrate foods with higher fibre versions most of the time.

5. Include some dairy

Some research suggests that yogurt and cheese may both help to lower the risk of type 2 diabetes. Choose plain varieties of yogurt to keep sugar intakes lower and sweeten with fruit. Cheese is high in saturated fat and salt so keep portions small, around the size of a small matchbox. We don’t know whether plant-based yogurts or cheese would have the same benefits, but if you do have these, choose those that are fortified with calcium. It’s important to remember that dairy foods like hard cheese and full fat yogurt are higher in fat and calories. So, for weight control it is best to choose reduced fat versions.

6. Cut down on red and processed meat

Research shows a link between the development of type 2 diabetes and higher intakes of red meat - especially processed meat. Red meat includes beef, lamb and pork and processed meat includes products such as bacon, ham, sausages, salami, and other cured meats, Swapping meat for beans, lentils, chickpeas, tofu, nuts and seeds, makes it easy to get enough protein and adds fibre to the diet.

Be more physically active

Increasing physical activity is a key factor in reducing the chances of developing type 2 diabetes, with studies showing it can lower the risk by 25 to 40%.

If you’re not currently active, start gradually by sitting less, standing more and incorporating small changes like using stairs instead of lifts or walking short distances rather than driving. You could also speak to your GP to get advice and find out about support available in your area.

Aim to build up to at least 150 minutes of moderate-intensity activity each week, spread out over at least four to five days such as 30 minutes a day, five times a week. Exercise that’s moderately intense should make you breath faster, feel warmer and increase your heart rate. This includes activities such as brisk walking, cycling, or dancing.

It’s also important to do muscle-strengthening activities at least twice a week. Examples include yoga, pilates, lifting weights or bodyweight exercises such as sit ups and push ups.

The NHS website provides plenty of resources on physical activity, including advice on walking for health, exercise guidelines, and the Couch to 5k programme.

Manage your weight

There is a strong link between living with overweight or obesity and developing type 2 diabetes. Losing weight, if needed, and avoiding weight gain over time, can dramatically reduce this risk.

Even modest weight losses can make a big difference. Studies show that losing just 5-7% of body weight can halve the risk of developing type 2 diabetes. For example, in someone weighing 100kg (15st 7lb) that would mean losing 5-7kg (11-15lb).

Losing a little more weight brings even greater benefits. A 10% weight loss – such as 10kg (22lb) in someone who weighs 100kg – can reduce the future risk of type 2 diabetes by 80%.

Maintaining weight loss is just as important. Research shows that maintaining a weight loss of 5% for three years reduces the risk of developing type 2 diabetes by 89%.

Overall, for each kilogram lost, the risk of developing type 2 diabetes drops by 16 percent.

There are many plans that support weight loss. The key is to find one that works for you. A plan should fit around your lifestyle, budget and food preferences, while promoting eating habits you can stick with long term. Ideally, a plan should follow the principles of the Eatwell Guide. This means it should be rich in plant-based foods such as wholegrains, vegetables and fruit, with moderate amounts of animal products if you choose to eat them. Foods that are high in fat, salt or sugar should be limited, for example, sugary drinks, biscuits, cakes, pastries and fatty meats. Calorie and portion control are also important components of a weight loss plan.

The NHS website provides several resources, including a 12-week weight loss plan, to support weight management.

Prediabetes FAQs

Should I use a continuous glucose monitor if I have prediabetes?

If you have been diagnosed with prediabetes, your GP will monitor your blood sugar levels regularly, usually at least once a year. However, if you experience any symptoms of type 2 diabetes, you should see your GP sooner.

It’s not known whether using a continuous glucose monitor helps to prevent people with prediabetes developing type 2 diabetes. While these devices could help people to identify foods that cause sharp blood glucose increases the results may not always be easy to interpret and could cause unnecessary anxiety. As well as the fact that the devices themselves are expensive. The best evidence for reducing risk of type 2 diabetes is for eating a healthy diet, being more physically active and losing weight, if needed.

Will a Soup and Shake Diet prevent prediabetes?

There are many diets designed to help people lose weight. Total Diet Replacement plans, sometimes known as ‘Soup and Shake’ diets, replace all regular meals with shakes, soups and bars. These diets typically provide around 800-1200 calories a day and provide all the protein, vitamins and minerals needed to stay healthy.

Research shows that following Total Diet Replacement plans for three to five months can lead to significant weight loss and put type 2 diabetes into remission for people living with obesity. While many people find it hard to stay in remission, there are still health benefits to achieving this, even if only for a short time. If following this type of diet it’s important to think about how to change eating habits over the longer term to help maintain weight loss when the programme is finished.

More research is needed to determine if Total Diet Replacement plans are more effective than other weight loss plans in preventing the progression of prediabetes into type 2 diabetes. However, losing weight is a key factor in lowering the risk of type 2 diabetes. The most important thing is to find a diet plan that works best for you.

Will avoiding or eating fewer carbs prevent prediabetes?

There’s no evidence that the amount of carbohydrates (carbs) in a person’s diet directly increases the risk of type 2 diabetes. However, eating plans that moderately restrict carbs have been linked to a reduced risk, although they’re not the only type of diet shown to achieve this. The Mediterranean Diet, DASH Diet, and vegetarian and vegan diets, have all been shown to help prevent type 2 diabetes.

Sugar is a type of carbohydrate and high intakes of sugar have been linked to excess calorie intakes, which in turn increase the risk of weight gain. So minimising intake of sugary foods and drinks is an important part of a healthy diet for prevention of type 2 diabetes.

Losing weight, if needed, is a key factor in lowering the risk of type 2 diabetes. Low-carb diets (those with less than 130g carbohydrate a day) can be suitable for weight loss, but they’re not any more effective nor do they result in greater weight loss than other types of diet.

It’s important to remember the Eatwell Guide includes carbohydrates as part of a balanced diet. The key is to choose wholegrains and foods high in fibre, both of which have been linked to a lower risk of type 2 diabetes.

Last reviewed September 2024. Next review due September 2027.