I have hair loss problem. and dandruff on my head. can't get rid of dandruff. is my hair fall due to dandruff? thyroid is ok. no heredity of hair fall

Separate problems.: The real name for "dandruff" is seborrheic dermatitis. Effective otc shampoos all contain either tar, salicylic acid, zinc pyrithione, selenium sulfide, or a combination of them, so look for those ingredients. Dandruff does not cause hair loss, so that is a separate issue, with many possible causes. Your dermatologist will have to run some tests to determine the cause.