What it is
Prediabetes is blood glucose raised above the normal range, but not yet at the level of type 2 diabetes. You may also hear it called non-diabetic hyperglycaemia, impaired fasting glucose, or impaired glucose tolerance, depending on which test found it.
Symptoms to look out for
Raised blood sugar in prediabetes usually causes no symptoms. The insulin resistance behind it can show up as:
- A larger waist, and difficulty losing weight
- Low energy and tiredness
- Sometimes low mood
- Raised blood pressure
- Darker skin on the neck, armpits and groin, and skin tags
Diagnosis is by blood test, most often HbA1c. In the UK the prediabetes range is 42–47 mmol/mol (6.0–6.4%).
Who is at risk
Excess weight around the middle, low muscle mass, inactivity, a diet high in sugar and ultra-processed food, increasing age, poor sleep and longer-term stress all raise the risk. So do a family history of type 2 diabetes, diabetes in a past pregnancy (gestational diabetes) and PMOS (also known as PCOS). Risk is also higher in South Asian, African and African-Caribbean backgrounds.
Often reversible, and worth acting on early
By the time blood sugar reaches the prediabetes range, insulin resistance has usually been building for several years, often alongside a larger waist and fat in the liver. Because it is largely driven by lifestyle, it responds well to lifestyle change, often within weeks to a few months. Many people can return their blood sugar to normal.
What you can do
- Food. Reduce sugar, sugary drinks, refined carbohydrate and ultra-processed food. Build meals with plenty of protein and non-starchy vegetables, with starchy carbohydrate reduced, or adjusted to the amount that suits you. See the Metabolic Health 28 Day Plan at healthshelf.org/28-day-plan.
- Movement. Aim for at least 150 minutes of moderate activity a week, and a walk after meals is particularly useful. Add resistance (strengthening) sessions at least twice a week to build muscle, which takes up glucose.
- Sleep and stress. Aim for 7 to 9 hours of regular sleep, as poor sleep worsens insulin resistance. Reduce long-term stress where you can.
- Keep track. You can use a glucose sensor worn on the arm to see how meals affect you. Re-check your HbA1c after about three months of changes, and at least once a year.
Medicines and supplements
Metformin is sometimes considered, and modified-release metformin is licensed in the UK for people at high risk whose blood sugar keeps rising despite lifestyle change. Lifestyle change is usually the more effective option and is tried first. A vitamin D3 or magnesium supplement may help a little, mainly if your levels are low. Discuss any supplement with a pharmacist or clinician.
When to get help
- If you have been told you have prediabetes, arrange follow-up to agree a plan and a monitoring schedule (usually once a year).
- If you are at higher risk, ask your GP practice about a blood test: NICE advises one at least every three years, and once a year if a result has already been in the prediabetes range.
- See a doctor promptly if you develop excessive thirst, passing a lot of urine, unexplained weight loss, ongoing tiredness or blurred vision.