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About olmesartan

Olmesartan is a medicine used to treat high blood pressure (hypertension).

It lowers your blood pressure and makes it easier for your heart to pump blood around your body.

Treating high blood pressure helps prevent future strokes, heart attacks and kidney problems.

It's only available on prescription and comes as tablets.

Key facts

  • It usually takes about a week for olmesartan to start reducing high blood pressure. It may take 2 to 8 weeks to take effect fully. The main side effects of olmesartan are feeling dizzy, headaches and flu-like symptoms, but they're usually mild and only last for a short time.
  • If you're being sick (vomiting) or have severe diarrhoea because of a stomach bug or illness while taking olmesartan, tell your doctor. You may need to stop taking it until you feel better.
  • If you're going to be put to sleep (have a general anaesthetic) for an operation or dental procedure, tell the doctor or dental surgeon that you're taking olmesartan. General anaesthetics can reduce your blood pressure.
  • Do not use salt substitutes such as Lo-Salt. This is because they are high in potassium. When mixed with olmesartan, they may make the level of potassium in your blood too high.

Page last reviewed: 14 February 2022
Next review due: 14 February 2025