Question 1

Do I need to fast for a CBC?

Accepted Answer

No. Food does not affect a CBC. If ferritin, iron or other tests are drawn at the same time, your clinician may ask you to fast or come in the morning.

Question 2

Can I have iron deficiency with a normal hemoglobin?

Accepted Answer

Yes. Iron stores run down before hemoglobin falls, so ferritin can be low while the CBC still looks normal. Tiredness, hair shedding or restless legs can appear at this stage.

Question 3

What is the difference between MCV and MCH?

Accepted Answer

MCV is the average size of your red cells; MCH is the average amount of hemoglobin in each one. They usually move together: both are low in iron deficiency and both are high when B12 or folate is low.

Question 4

Should I take iron or B12 if my CBC is off?

Accepted Answer

Not before the cause is known. Iron taken when you do not need it can build up in the body, and starting iron or B12 can blur later tests. Talk to your clinician about which test comes next.