Telmisartan is an angiotensin II receptor blocker (ARB) used primarily to treat high blood pressure (hypertension) and to reduce the risk of heart attack or stroke. It works by blocking the action of angiotensin II, a hormone that causes blood vessels to constrict, thereby relaxing blood vessels and lowering blood pressure. Telmisartan can also be used in combination with other antihypertensive agents to manage more difficult cases of high blood pressure.