Olmesartan: What It Does and How to Use It

Olmesartan is a prescription drug used to lower high blood pressure. It belongs to a group called angiotensin II receptor blockers (ARBs). If your doctor prescribes olmesartan, the goal is simple: reduce strain on your heart and lower the risk of stroke or heart attack over time.

How olmesartan works

Olmesartan blocks a hormone (angiotensin II) that tightens blood vessels. When those vessels relax, blood flows easier and pressure drops. Most people start on a low dose—often 20 mg once daily—and the doctor may increase it to 40 mg if needed. You can take it with or without food, but try to take it the same time every day so you don't forget.

Expect to see blood pressure improvements in a few weeks, but full effects can take longer. Keep using it even if you feel fine; high blood pressure often has no symptoms, and stopping suddenly can undo the benefit.

Safety tips and monitoring

Common side effects include dizziness, tiredness, and sometimes stomach upset. Less common but important issues are high potassium and changes in kidney function. Your doctor will usually check blood tests for potassium and creatinine before starting and after dose changes.

Don't use olmesartan if you're pregnant. ARBs can harm a developing baby. If you plan to become pregnant or discover you're pregnant, tell your doctor right away so they can switch your medicine.

Tell your doctor about other medicines you take. Combining olmesartan with potassium supplements, potassium-sparing diuretics, or certain blood pressure drugs can raise potassium too much. Also mention NSAIDs, lithium, or any herbal supplements—some combinations affect kidney function or reduce how well olmesartan works.

If you have kidney problems, liver issues, or a history of low blood pressure, your doctor will pick the safest dose and monitor you more closely. Older adults may be more sensitive to dizziness or drops in blood pressure when standing up, so stand slowly and be cautious at first.

There’s a rare but serious intestinal side effect called sprue-like enteropathy, which causes severe, persistent diarrhea and weight loss. It’s uncommon, but if you get those symptoms and they don’t stop, contact your doctor and mention olmesartan as a possible cause.

Want quick practical tips? Take olmesartan at the same time daily, avoid sudden position changes, keep track of home blood pressure readings, and bring a current medicine list to appointments. Never share prescriptions and always check with your prescriber before stopping or changing the dose.

If you need help deciding whether olmesartan fits your situation, talk to your doctor or pharmacist. They can explain how it compares to other blood pressure meds and help you find the safest option for your needs.