Why Your A1c Doesn’t Tell the Whole Story About Insulin Resistance
Point One: A1c is not a measure of insulin resistance
Hemoglobin A1c has become the go-to test for diabetes screening. It tells you your average blood sugar over the past two to three months, which is valuable — but it says nothing about how hard your body is working behind the scenes to keep those numbers steady. You can have a perfectly normal A1c while your pancreas is secretly pumping out two or three times the normal amount of insulin. That hidden strain is insulin resistance, and A1c simply doesn’t capture it.
Point Two: Where the misconception comes from
So why do so many people — including doctors — assume A1c reflects insulin resistance? Three reasons:
Convenience: A1c is cheap, standardized, and widely available. It became the routine screening tool, and what’s routine is often mistaken for comprehensive.
Messaging: Public health campaigns frame diabetes as a “high blood sugar problem,” not a “high insulin problem.” That language blurs the distinction between outcomes (glucose levels) and causes (insulin resistance).
Correlation confusion: People with high A1c often also have insulin resistance, so the two get lumped together. But plenty of people have normal A1c and significant resistance — they just haven’t tipped over yet.
Point Three: When A1c is high, the next step is an OGTT
If your A1c is 6.0 or above, that means there is already too much glucose circulating in your blood. At that point, you need a deeper look — and that’s where the Oral Glucose Tolerance Test (OGTT) comes in.
Here’s how it works:
You fast overnight.
A baseline blood sample is taken.
You drink a standardized glucose solution (usually 75 grams).
Your blood is drawn again at one and two hours after the drink.
What the results show:
In someone with good insulin sensitivity, blood sugar rises modestly and returns near baseline within two hours.
In someone with insulin resistance, the body responds with an exaggerated insulin surge — glucose rises higher and often stays elevated longer. Even if glucose falls back to normal by two hours, unusually high insulin levels reveal the hidden struggle.
That’s the critical difference: the OGTT shows how your body handles stress, not just where it sits at rest. It’s the practical way to measure insulin resistance before diabetes has fully set in.
Conclusion
A1c is a valuable tool, but don’t mistake it for a full picture of metabolic health. Insulin resistance develops quietly and can exist long before A1c drifts upward. If your A1c hits 6.0 or higher, don’t stop there — an OGTT will tell you whether your body is fighting a hidden battle with insulin, and give you a much clearer map of where your metabolism stands.