Your doctor will tell you when to stop. But let your doctor know what other medicines you're taking. This is especially important for women on the birth control pill, and for anyone on methadone. And you should try to avoid alcohol while taking your TB medicine. In most cases, no.
Some people have a loss of appetite, or get a rash.
If you have either of these problems, or notice anything else unusual, tell your doctor or nurse. If you get a yellowing of the eyes, or have dark brown urine, stop taking your medicine and tell your doctor. The TB can come back even worse, and you might spread it to others. You might even die. If you think that taking your medicine is going to be hard to do, ask your doctor about programs that can help you follow your doctor's orders.