# Quick Hb1Ac question

#### merrio

Hb1Ac is generally measured in mmol/mol, although often also in percentages.
What I don't get is why the mmol/mol isn't simply a tenfold of the percentage. mmol/mol basically means 1/1000th right? And percentage means 1/100th. Or am I missing something?

#### Ismet

##### PGY-almost done!
Moderator Emeritus
7+ Year Member
No....that is not how it works.

You can't just multiply a % HbA1c by 10 and magically come up with mmol/mol. Units don't work that way.

The equation for conversion is HbA1c (in mmol/mol) = ( HbA1c (%) - 2.15 ) x 10.929

That said, I've never encountered anyone who uses the mmol/mol format in clinical medicine in the United States.

mistafab

#### SurfingDoctor

##### "Hooray, I'm useful"
10+ Year Member
What I don't get is why the mmol/mol isn't simply a tenfold of the percentage. mmol/mol basically means 1/1000th right? And percentage means 1/100th. Or am I missing something?
Molarity is a concentration based on a molecular weight. Without knowing the actually number, I assume glycosylated hemoglobin has a higher molecular weight than non-glycosylated hemoglobin, so you can't just divide by 1000. Percentage doesn't account for differences in weight and thus is a straight ratio of one to the other. That is why the two measurement don't exactly match.

#### Donald Juan

7+ Year Member
What the hell?? mmol/mol?

mistafab