High HbA1c Levels Do Not Always Lead to Diabetes

Prediabetes is an asymptomatic condition preceding type 2 diabetes. It is characterized by hyperglycemia, which is defined as a blood glucose level that is higher than normal but below the level for a clinical diagnosis of diabetes.

Glycated hemoglobin (HbA1c) values increase with age amongst diabetes‐free subjects, and low glucose level may increase mortality in old age. Questions remain on which factors are related to the reversion from prediabetes to normoglycemia, independently of mortality amongst the older population.


Scientists at the Karolinska Institute (Stockholm, Sweden) followed 2,575 men and women aged 60 and older without diabetes for up to 12 years. At the start of the study, 918 people, or 36% of the group, did have higher-than-normal blood sugar levels that were still below the threshold for diabetes.

HbA1c was collected at regular interval and until December 2010, HbA1c was assessed with Swedish Mono‐S filament High Performance Liquid Chromatography, and 1.1% was added to the individual's values to render them equal to international values in accordance with National Glycohemoglobin Standardization Program (NGSP; HbA1c in %). Since 1 January 2011, HbA1c has been assessed with the International Federation of Clinical Chemistry (IFCC) reference method. A standard equation (NGSP = [0.9148 * IFCC] + 2.152) was applied to convert IFCC HbA1c (in mmol mol−1) to NGSP value (in %), to render HbA1c results from all waves comparable.

The scientists reported that only 119 people, 13% of those who started out with elevated blood sugar, went on to develop diabetes. Another 204, or 22%, had blood sugar levels drop enough to no longer be considered prediabetic. Obese adults with prediabetes were more likely to progress to full-blown diabetes. Ying Shang, MMSc, of the Aging Research Center at the Karolinska Institute and first author of the study, said, “Progressing to diabetes is not the only destination. In fact, the chance to stay prediabetic or even revert back to (normal blood sugar) is actually pretty high (64%), without taking medication. Lifestyle changes such as weight management or blood pressure control may help stop prediabetes from progressing.” The study was published on June 4, 2019, in the Journal of Internal Medicine.

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Karolinska Institute