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Angiotensin II receptor blocker (ARB)

Losartan: uses, side effects & precautions

Also known as Cozaar, Losacar, Lortaan.

This information is for general guidance only and does not constitute medical advice. Always consult a qualified healthcare professional for personal medical concerns. In an emergency, call your local emergency number.

What it is used for

  • High blood pressure (hypertension)
  • Protecting the kidneys in people with type 2 diabetes
  • Reducing stroke risk in people with high blood pressure and an enlarged heart
  • Heart failure in some people

How it works

Losartan blocks the action of a hormone (angiotensin II) that tightens blood vessels. By stopping that hormone from working, blood vessels stay relaxed and wider, which lowers blood pressure and eases strain on the heart and kidneys.

How it is taken

Taken by mouth as a tablet, usually once a day with or without food. Take it exactly as your doctor or pharmacist directs and follow the label. Do not stop on your own; your clinician may check your kidney function and potassium with blood tests.

No doses here on purpose. The right strength and schedule depend on you — only a doctor or pharmacist should set them. Always follow your prescription and the label.

Common side effects

  • Dizziness, especially when standing
  • Tiredness
  • Headache
  • Mild rise in blood potassium
  • Stuffy nose or cold-like symptoms

Serious effects — get help

  • Swelling of the face, lips, tongue or throat, or trouble breathing (angioedema) — seek emergency care
  • Fainting
  • Signs of high potassium such as muscle weakness or irregular heartbeat
  • Reduced urination or signs of kidney problems

If a reaction is severe — for example trouble breathing, swelling of the face or throat, or collapse — go to the nearest emergency room now or call your local emergency number. Do not wait for an online consultation.

Interactions to watch

  • Potassium supplements and potassium-containing salt substitutes
  • Potassium-sparing diuretics such as spironolactone
  • Other blood pressure medicines, especially ACE inhibitors (avoid combining without advice)
  • Non-steroidal anti-inflammatory drugs such as ibuprofen
  • Lithium

Who should take care

  • Do NOT use in pregnancy — it can harm the unborn baby; tell your doctor if you become or plan to become pregnant
  • Tell your clinician about kidney disease or narrowing of the kidney arteries
  • Avoid potassium-based salt substitutes unless advised
  • Dizziness risk is higher if dehydrated or also taking a water pill
  • Discuss liver problems with your clinician

Frequently asked questions

How is losartan different from lisinopril?
Both lower blood pressure by acting on the same hormone system, but losartan (an ARB) blocks the hormone's receptor and rarely causes the dry cough seen with ACE inhibitors. Your clinician chooses based on your needs.
Can I take it during pregnancy?
No. Like ACE inhibitors, ARBs can harm a developing baby. Tell your doctor right away if you are or may become pregnant.
Will it make me cough like some other BP pills?
A dry cough is much less likely with losartan than with ACE inhibitors, which is one reason it is sometimes preferred. Report any persistent cough anyway.
Do I need blood tests on this medicine?
Yes, your clinician may check kidney function and potassium periodically to make sure the medicine remains safe for you.
Is Losartan safe to take?
For most people it is safe when taken exactly as a doctor or pharmacist advises and as printed on the label. Tell your clinician about your other medicines and health conditions, and seek urgent care for any serious reaction.

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