What does your HbA1c tell you about your risk of diabetes and ageing?
An elevated HbA1c, even well below the official diabetes threshold, is associated with a greater risk of diabetes, kidney damage, eye complications and possibly dementia. Have your HbA1c checked regularly and discuss with your doctor what a healthy target value is for you.
HbA1c is a measure of your average blood sugar over the past two to three months. A value of 5.7% or higher in children and young adults (ages 10-19) increases the likelihood of developing type 2 diabetes later in life by four to seven times compared with peers who have an HbA1c of 5.3% or lower. Notably, HbA1c predicted that risk just as well as a fasting blood glucose measurement or an oral glucose tolerance test.
Once you have diabetes, what matters is not only how high your HbA1c is, but also how stable it remains over time. Large fluctuations are associated with a 26 to 53% higher risk of kidney function loss, regardless of the average value. Stable blood sugar control is therefore at least as important as achieving a good average value. In addition, a high HbA1c is one of nine factors that predict whether someone with diabetes will develop early kidney complications, based on data from more than 41,000 patients.
A chronically high HbA1c also has consequences for other organs. In people with type 2 diabetes who start blood-sugar-lowering medication (SGLT2 inhibitors), one observational study found that an HbA1c of 9% or higher was associated with a greater risk of dementia, particularly caused by vascular damage in the brain. This association weakened considerably after correction for other factors, so it does not yet constitute a proven cause-and-effect relationship. Serious eye complications (sight-threatening retinopathy) are also associated with a higher HbA1c, alongside diabetes duration and blood pressure.
Good news: a small study (47 participants, without a control group) showed that continuous glucose monitoring in people with type 2 diabetes who do not use insulin produced measurable improvements in blood sugar, weight, blood pressure and cholesterol. Placebo effects and extra medical attention may have played a role, so this result calls for confirmation in larger studies.
Finally: even in people who have had a kidney transplant, an HbA1c of 5.3% or higher proved sufficient to identify a high-risk group for post-operative diabetes. This was investigated retrospectively at a single hospital, but it shows that being 'still normal' on the standard scale does not automatically mean there is no elevated risk.
Claims are based on multiple large associational studies and meta-analyses (up to 41,271 participants). Cause and effect has not been proven; virtually all findings involve associations. The continuous glucose monitoring study has no control group (n=47). The kidney transplant study is retrospective and single-centre.
What is a healthy HbA1c value?
In healthy adults, a normal HbA1c falls between roughly 4.79% and 6.15%, with an average of 5.47%. If your value is above this, discuss it with your general practitioner to rule out prediabetes or diabetes.
How often should you have your HbA1c measured?
In stable diabetes, measuring twice a year is standard; when values fluctuate or treatment has changed, four times a year is the norm. Discuss the frequency that suits you best with your doctor.
Can your HbA1c also be too low?
An HbA1c below 5.0% is associated with an increased risk of death in people without diabetes, although this is likely a signal of an underlying condition. Always have a strikingly low value investigated by your doctor.
Does someone with diabetes age faster biologically?
Yes, diabetes noticeably accelerates biological ageing: the risk of cardiovascular disease, dementia, and premature death increases, and keeping blood sugar well under control is the most direct way to slow that process.
How do you lower a high HbA1c?
Several medications demonstrably lower HbA1c: the weekly semaglutide injection has the strongest evidence base, but oral combinations involving empagliflozin or semaglutide also offer good evidence. Discuss with your doctor which option suits your situation, side-effect profile and reimbursement coverage.
How do I know if my blood sugar is healthy (prediabetes)?
Prediabetes can be measured reliably, but no single blood test provides complete certainty on its own. If in doubt, have multiple values measured and discuss with your doctor whether a lifestyle programme or medication is worthwhile, because that difference has been proven to matter.