High blood pressure, protection of the kidneys in type 2 diabetes with protein in the urine, heart failure, and reducing the risk of stroke in people with high blood pressure and a thickened heart muscle.

The body makes a hormone called angiotensin II that tightens blood vessels and holds on to salt and water, both of which push blood pressure up. Losartan blocks the receptor angiotensin II acts on, so the vessels stay relaxed, the kidneys let go of excess salt and water, and the pressure inside the kidney's filters falls.

Dizziness, especially with the first doses or on standing up, tiredness, headache and a raised potassium level on blood tests. Unlike ACE inhibitors it rarely causes a cough.

Do not take losartan in pregnancy: it can seriously harm the baby, and anyone who could become pregnant should discuss this before starting. Blood tests check kidney function and potassium, so keep to them, and avoid potassium supplements or salt substitutes unless your doctor agrees. Take care with NSAIDs such as ibuprofen, which blunt the effect and strain the kidneys, and stand up slowly at first. It is a prescription medicine in Pakistan.