My 4 year old hemoglobin is 6.6, hematocrit 24.6, and rdw is 21.5. need your opinion on whats is going on. thank you ?

Anemic: It is obvious the kid is anemic to a degree many consider transfusion as appropriate treatment. You get this anemic from: Blood loss either short term or over time; failure to make blood to replace what wares out; or blood break down. Beyond this, your post does not provide enough information for any other analysis.

Agree with Dr. F: The hemoglobin of your child is too low and you ought to consult a doctor at your earliest. It is not feasible to provide a meaningful opinion without additional history, physical examination and may be some tests.