For how long do you have to take medicines for paranoia?

Lifetime: If your paranois is the result of schizophrenia, it is likely that you would benefit from treatment throughout your lifetime. Please follow the advice and recommendations of your psychiatrist. Having a thought disorder is a very frightening experience but there is treatment that can help you live your life well and successfully.

It depends: As in many instances paranoia itself doesn't require medications. Treatment options depend very much on what's causing the paranoia, other associated symptoms like hallucinations, and dysfunction related to this.