Is it normal that my platelet count has changed from 146 to 150 after 4 months of taking iron? isnt it slow ?

Same numbers: In the grand scheme of things, 146,000 and 150,000 are the same number when counting platelets. There is no difference. Life is not exact. Sometimes numbers like these make a difference to what a doctor is thinking, but generally not. For example, putting the same blood draw into 2 separate tubes and sending both tubes to the lab might give you 146,000 in one tube and 150,000 in the other tube.