Treats high blood pressure. These prescriptions are used to lower high blood pressure and work by relaxing blood vessels. Angiotensin II is a chemical that the body releases to cause the constriction of blood vessels. Candesartan blocks the action of angiotensin II, resulting in the relaxation of the blood vessels. This relaxation causes the blood pressure to decrease. It takes about 2 weeks for the drug to begin to the lower your blood pressure, and about 4 weeks for it to reach its full effect. Your doctor may choose to use this prescription for other conditions. If you're unsure why you are taking this prescription, contact your doctor.