Mu daughter has just turn 15 and have not have her period yet she is ver heslthy. when should i consider taking her. to the doctor?

Depends: May sound weird but, depends on breasts. If she has started having secondary sex characteristics (breast buds) then it could be normal not to have a period until age 16. If she has not yet started to develop breast buds then she probably should go see a doctor sooner to make sure nothing else is going on.

Yes: Failure to have breast buds by 13 and/or menses by 15 is a good reason for a complete history/exam and appropriate testing.Do it soon.