Irbesartan is in a group of drugs called angiotensin II receptor antagonists. Irbesartan keeps blood vessels from narrowing, which lowers blood pressure and improves blood flow. Irbesartan is used to treat high blood pressure (hypertension). It is sometimes given together with other blood pressure medications. Irbesartan is also used to treat kidney problems caused by type 2 diabetes. Irbesartan may also be used for purposes not listed in this medication guide.