In people with type 2 diabetes, certain blood traits like red blood cell size and count might change A1c levels — not because of blood sugar, but because of how those cells are made. So, your A1c might look high or low even if your sugar control is fine.

Men and women with type 2 diabetes show similar links between blood cell traits and A1c levels, so doctors can use the same A1c rules to monitor both.

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.

Type 2 diabetes means your blood sugar stays too high over time, and doctors check this with two tests: one after you've fasted and another called HbA1c that shows how much sugar has been sticking to your red blood cells over the past few months.

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.

In people with type 2 diabetes, a blood test measure called RDW doesn’t seem to be linked to their average blood sugar levels (A1c), so it probably doesn’t affect how doctors read those A1c results.