why do i have flat fingernails

Hello and thank you for sharing your question.

Four common reasons for flat nails are thyroid conditions, vitamin B12 deficiency, protein deficiency, and/or anemia.  There are other less common reasons, but I suggest you start with these.  You can start taking Vitamin B12 and oral Iron pills right away.  Then perhaps get your thyroid examine and also be test for protein deficiency.

If none of these seem to be the cause than it could be Diabetes, or Psoriasis.  But I suggest you rule out the first possibilities before looking at these.

Faith