Who will know?
Generally, medical information is kept confidential between the patient and health care provider. Positive results for some STDs, like HIV or syphilis, may be shared with state or city health departments for tracking purposes, but there are laws preventing health departments from sharing your test results with your family, friends, or employer. If you use health insurance to get tested, you should consider who else has access to that information (like a parent or partner if you share health insurance). Be sure to ask your health care provider who will know that you got tested and who will know your results, especially if you are using insurance. Ask questions and stay informed.
If you are under 18, there are places where you can get confidential testing without parental permission, meaning your parents don’t need to give permission for you to be there, and they won’t be contacted by the clinic. Your parents won’t even know that you were there. When making your appointment for STD testing, ask about the health center’s privacy policies: Will they call you at home with test results? Will they send a bill to you? Will they send other mail? Every facility works differently—it’s OK to ask.