Can a doctor tell if you've been masturbating?
Usually, a doctor cannot tell if a girl or guy has been masturbating. The only way it might show is if masturbation has irritated the penis or vaginal area enough that there is obvious redness.
If a girl inserts something into her vagina and tears her hymen, a doctor will probably notice that. But the doctor won't know what caused the hymen to tear.
Masturbation isn't something to be embarrassed about or ashamed of. If you have questions about it, your doctor is the best person to ask. There are lots of myths out there about masturbation. (No, it doesn't stunt your growth, and it won't make you blind, although these rumors keep going around!) Your doctor is the best person to give you the correct information when it comes to masturbation or any other health issue.