Rethinking Diabetes Diagnosis in Obese Population with Suspected Prediabetes: Screening Tool or Final Word?

Dr Ashok Kumar, Dept. of Endocrinology, Cedar Clinic, Panipat, Haryana, India

In obesity-driven prediabetes, HbA1c alone may underestimate progression, making OGTT essential to accurately detect those who have already developed diabetes.

As obesity continues to drive the global rise in type 2 diabetes, clinicians are increasingly relying on HbA1c as a convenient diagnostic shortcut. But new research suggests that in people living with obesity, that shortcut may not always tell the full story.

A recent single-center study evaluated 139 adults with obesity referred for suspected prediabetes between 2020 and 2022. The average participant was 45 years old, and more than 80% were women. Nearly half met the criteria for morbid or super obesity.

When researchers performed the standard 75-gram oral glucose tolerance test (OGTT), the results were sobering. While 37.4% had isolated impaired fasting glucose and 45.3% had combined fasting and post-load abnormalities, 17.3% were newly diagnosed with overt type 2 diabetes. These were not borderline cases—they were individuals whose diabetes may have gone undetected without formal glucose tolerance testing.

HbA1c did correlate with fasting glucose levels, and a threshold of 6.15% provided the best balance for detecting diabetes confirmed by OGTT, with a strong negative predictive value of 95.8%. Yet the broader message is clear: HbA1c is a useful screening signal, but it is not foolproof.

In an era that prioritizes efficiency, it is tempting to treat HbA1c as definitive. But in patients with obesity, where metabolic complexity is the rule rather than the exception, precision matters. The oral glucose tolerance test may be less convenient, but it remains a crucial safeguard against missed diagnoses.

The takeaway is not to abandon HbA1c, but to resist overconfidence in a single number. When it comes to diabetes detection in obesity, confirmation still counts.

(Source: Budak A, Solmaz I, Alakuş ÖF, Başgöz BB. Diagnostic Performance of HbA1c for Detecting OGTT-Diagnosed Diabetes in Obese Individuals with Suspected Prediabetes. Journal of Clinical Medicine. 2026 Jan 4;15(1):374. )