This question can be answered in two ways. You can take certain medications without doctor's prescription and there are medications that you need doctor's prescription before you can take them. Over the counter medications (OTC) do not need prescription. OTC are for common illnesses like headache, common cold, muscle and joint pain. Examples of OTC are aspirin, ibuprofen, naproxen and acetaminophen.
Conditions like hypertension and high blood pressure are treated with medications that must be prescribed by a doctor.