Doctors usually rely on the HbA1c blood test to see how well someone with diabetes has managed their blood sugar over time — but some experts are starting to question if it’s always accurate for everyone.

HbA1c might not give a true picture of blood sugar control in people with diabetes because things like how often blood sugar swings, different ethnic backgrounds, and other health problems can affect the results.

Sometimes, blood sugar tests that don’t use HbA1c might give a better picture of how well someone’s diabetes is managed—especially if things like blood disorders or other health issues make the standard HbA1c test less reliable.

HbA1c tells you how much sugar has been sticking to your blood cells over the past few months — it's like a long-term blood sugar report card.

If someone has certain blood conditions like sickle cell trait, their A1c test might show lower blood sugar levels than they actually have, which could trick doctors into thinking diabetes is under control when it's not — especially if they don't also check regular blood sugar tests.

HbA1c might show high blood sugar even in people who actually have normal levels, because some people's red blood cells live longer than usual.