Prediabetes: What Your A1C Result Really Means and What to Do Next

A retired teacher stood at my counter turning a lab slip over in her hands. "It says 6.1," she said. "The nurse told me I have prediabetes and to cut back on sugar, and then she was called away. Is that the same as diabetes?" Her prediabetes A1C result was a number she had been given with no explanation, which is more common than it should be.

The short answer is no, it is not diabetes. It is a warning light, not a diagnosis, and it is one of the few warnings in medicine that you can often act on before anything has gone wrong.

What an A1C test measures

The A1C test shows your average blood sugar over roughly the past three months. It works by measuring how much sugar has stuck to the hemoglobin in your red blood cells. You do not need to fast, which is why it is so widely used.

The US National Institute of Diabetes and Digestive and Kidney Diseases (NIDDK) gives these ranges:

| Result | A1C | |---|---| | Normal | below 5.7% | | Prediabetes | 5.7% to 6.4% | | Diabetes | 6.5% or above |

UK and many African laboratories report A1C in millimoles per mole (mmol/mol). Diabetes UK lists normal as below 42, prediabetes as 42 to 47 and type 2 diabetes as 48 or above. Two other blood tests can also show prediabetes. A fasting glucose of 100 to 125 mg/dL (5.6 to 6.9 mmol/L) counts, as does a result of 140 to 199 mg/dL (7.8 to 11.0 mmol/L) two hours into a glucose tolerance test.

What prediabetes actually means

Your blood sugar is higher than normal, but not high enough to be called diabetes. The NIDDK says people with prediabetes have a high chance of developing type 2 diabetes within 5 to 10 years. That is a risk, not a certainty. Many people with prediabetes never progress, especially if they make changes.

Prediabetes is common. The US Centers for Disease Control and Prevention (CDC) says that more than 2 in 5 American adults have it, and its national data page reports 115.2 million adults. Diabetes UK estimates around 1 in 12 people in the UK. Most do not know. The NIDDK notes that prediabetes usually has no symptoms, which is why a blood test is the only reliable way to find it.

Why one number can mislead

A1C is useful, but it is not perfect. The NIDDK lists several situations where it can be inaccurate:

• recent blood loss or a blood transfusion
• sickle cell disease or other conditions that change how long red blood cells live
• very low iron, which can falsely raise the result
• kidney failure or liver disease
• hemoglobin variants, which the NIDDK says are more common in people of African, Mediterranean or Southeast Asian descent

That last point matters for many of my readers. Some A1C methods give unreliable results in people with certain hemoglobin variants, and a different type of A1C test or a glucose test may be needed. If your result does not match how you feel, or your family has sickle cell trait, say so.

Also remember that one result is not a diagnosis. The NIDDK advises that if you have no symptoms, a result in the prediabetes or diabetes range should be confirmed with a repeat test on a different day. A finger-prick test in a pharmacy or clinic is a screening tool and should not be used on its own to diagnose.

Who should be tested

The US Preventive Services Task Force recommends screening adults aged 35 to 70 who are overweight or have obesity, and says that repeating the test every 3 years may be reasonable if results are normal. It also notes that a BMI of 23 or more may be an appropriate cutoff for Asian American adults. The NIDDK lists other risk factors: a family history of diabetes, being physically inactive, a large waist, sleep apnea, smoking, a history of gestational diabetes, polycystic ovary syndrome, and being African American, American Indian, Asian American, Hispanic or Latino, or Pacific Islander. Some medicines can also raise blood sugar, including glucocorticoids (steroid tablets), some antipsychotics and some HIV medicines. Do not stop any of these on your own. Ask your prescriber whether a blood sugar check is sensible.

In the UK, the NHS Health Check offers a diabetes risk assessment to adults aged 40 to 74, and Diabetes UK has a free "Know Your Risk" tool.

What to do next: what the trials show

The best evidence comes from the Diabetes Prevention Program (DPP), a US trial of 3,234 adults with higher-than-normal blood sugar and excess weight. After an average of 2.8 years:

• An intensive lifestyle program reduced the number who developed diabetes by 58% compared with placebo.
• Metformin reduced it by 31%.

The lifestyle goals were a loss of about 7% of body weight through a lower-calorie, lower-fat diet, plus at least 150 minutes of physical activity a week. For a person weighing 200 pounds (90 kg), 7% is about 14 pounds (6 kg). The NIDDK describes a 5% to 7% weight loss as helpful.

The CDC reports that the National Diabetes Prevention Program, built on this research, lowers the risk of type 2 diabetes by 58%, or 71% for people over 60. In England, the NHS Diabetes Prevention Programme offers a nine-month group or digital lifestyle program, and the NHS says completing it cuts the risk of type 2 diabetes by more than a third.

These are results from people who took part and are not a guarantee for any one person. But they show that ordinary, achievable steps move the numbers.

Practical steps to start this week

1. Move more, in ways you will keep doing. The NIDDK recommends at least 150 minutes of moderate activity a week, about 30 minutes on most days, and strength training twice a week. A brisk walk counts.
2. Look at what is on your plate. Fill half with non-starchy vegetables, and keep refined starches and sugary drinks in check (see our guide to type 2 diabetes foods for details that work with African staples as well).
3. Check your sleep. The NIDDK suggests 7 to 8 hours a night.
4. Stop smoking if you smoke. It is on the NIDDK's risk list.
5. Ask about a structured program. The programs above are built on the trial methods, and support can make habits easier to keep.
6. Plan a recheck. The NIDDK says people with prediabetes should be tested for type 2 diabetes every year.

What about metformin and other medicines?

Metformin was shown to delay diabetes in the DPP. According to the NIDDK, it worked best in women with a history of gestational diabetes, younger adults and people with obesity. The USPSTF adds that metformin is effective for this purpose but is not FDA approved for it, so prescribing is a judgment call between you and your clinician. Metformin often causes stomach upset, particularly at first. In the DPP, digestive symptoms were more frequent with metformin than with placebo. Taking it with food and building up slowly, as your prescriber directs, can help.

Newer weight-loss medicines can also lower blood sugar, but they are prescribed for weight, not for prediabetes itself. If weight is a major driver of your numbers, that is a conversation to have with your doctor.

Beware of supplements marketed for "reversing" prediabetes. The NIDDK states there is no clear proof that specific foods, herbs, spices or supplements manage diabetes, and some can interact with medicines.

Questions to ask your doctor or pharmacist

• Is my A1C result enough on its own, or do I need a repeat or another test?
• Could anything, such as anemia, sickle cell trait or kidney disease, make my A1C misleading?
• Do any of my medicines raise blood sugar?
• Is there a diabetes prevention program near me or online, and can you refer me?
• Would metformin make sense in my situation?
• When should I be retested?
• What targets should I set for weight, activity and food?

If you'd like the full guide, my book Reverse Prediabetes and Insulin Resistance goes deeper into understanding your blood results and lowering your A1C with a practical 30-day plan.

Sources

• National Institute of Diabetes and Digestive and Kidney Diseases. Insulin resistance and prediabetes
• National Institute of Diabetes and Digestive and Kidney Diseases. The A1C test and diabetes
• National Institute of Diabetes and Digestive and Kidney Diseases. Diet, eating and physical activity (diabetes)
• Centers for Disease Control and Prevention. Prediabetes: your chance to prevent type 2 diabetes
• Centers for Disease Control and Prevention. Diabetes data and research
• US Preventive Services Task Force. Prediabetes and type 2 diabetes: screening, final recommendation statement (2021)
• Diabetes Prevention Program Research Group. Reduction in the incidence of type 2 diabetes with lifestyle intervention or metformin. N Engl J Med. 2002;346(6):393-403.
• Diabetes UK. Prediabetes
• NHS England. NHS Diabetes Prevention Programme
• NHS. High blood sugar (hyperglycaemia)