Losartan is a medicine that is commonly used to treat high blood pressure and heart failure. It is also used to protect your kidneys if you have diabetes or kidney disease. Your doctor may prescribe losartan to help prevent kidney disease, strokes and heart attack.


How does Losartan work?

Losartan belongs to a class of medication called angiotensin II receptor antagonists. Angiotensin II is a chemical in your body that enters your blood stream and causes your blood vessels to begin to constrict. That thickens and stiffens the walls of your blood vessels and heart. It also causes a hormone in your body to make your body retain water. More fluid or sodium and water in your body together with the restricted space will cause your blood pressure to rise. Angiotensin II receptor antagonists work by blocking the production of this chemical in the blood. Hence, they relax and widen blood vessels which allows blood to flow through. It also reduces the volume of fluid and ultimately lower your blood pressure.

Who can I take Losartan?

Most adults over 18 can take Losartan.

Children who are aged 6 years and over can take also take it for treatment of high blood pressure only.

Some doctors will switch you from a class of medication called ACE inhibitors (e.g. Lisinopril or Ramipril) to Losartan if you are not able to take them because you experience a dry irritating cough which is a known side effect of that class of medicines.

Losartan isn’t suitable for some people.

Who can’t take Losartan

Losartan is not the most suitable medicines for certain people. It is important that you tell your doctor if you:

  • are planning to get pregnant, pregnant or breastfeeding.
  • have previously had an allergic reaction to losartan
  • have hypotension (low blood pressure)
  • are on a low salt diet
  • have diabetes
  • have liver, heart or kidney disease
  • have had a kidney transplant
  • have diarrhoea or vomiting

How to take Losartan

Losartan is usually taken once a day. It is advised that you take the first dose at bedtime as Losartan may cause you to feel dizzy. You can usually take the subsequent doses at any time of day. It is advised that you take it at the same time of day every day. Losartan can be taken with or without food

Take Losartan as directed by your doctor. Do not stop taking it even if you feel better.

What dose would I take?

The dose of losartan you will be prescribed will depend on weather you are taking it to treat hypertension of heart failure. Your doctor will usually tell you the dose you need.

Usually, adults’ dose for high blood pressure is 50mg to 100mg and between 12.5mg to 150mg once a day for heart failure

For children, the weight may be used to calculate the dose.

Why does my dose go up or down?

Your dose may need adjusting. After a few weeks of starting Losartan, you doctor may check you to see how well it is working and make any dose adjustment. Your doctor will measure your blood pressure, check for side effects, do a blood test to see the effect of Losartan on your kidneys and to check the levels of potassium. Based on all these, your doctor may decide to either increase or reduce the dose.  

What if I forget to take it?

Take it as soon as you remember if you forget to take your medicine but do not take a double dose to make up for a dose that you forgot to take.

What if I take too much?

See your doctor immediately if you take too much.

Side effects

Losartan just like all medicines can cause side effects. Not everyone will get these side effects and the side effects may reduce or stop when your body adjusts to the medication. Some common side effect includes:

  • Hyperkalaemia (High level of potassium
  • Hypotension (low blood pressure) and postural hypotension (low blood pressure on standing)
  • Asthenia (abnormal physical weakness or lack of energy)
  • Vertigo (Feeling like everything around you is spinning)
  • Nausea (feeling sick)
  • Vomiting (actually being sick)
  • Diarrhoea
  • Dizziness
  • Back pain
  • Renal impairment (Kidney problems)

Let your doctor or pharmacist know about any side effects that bothers you or persists.


Sometimes but very rarely, Losartan can cause angioedema which is an allergic reaction that causes swelling around the eyes, lips and tongue, hands, feet and genitals. In severe cases, the swelling can involve the inside of your throat and bowels. If it affects your throat, this can make you have breathing or swallowing difficulty.  You must contact your doctor immediately if you experience this.


Losartan isn’t recommended during pregnancy. However, your doctor might prescribe you it if they feel it is the best option for you or if they think the benefit of taking it outweighs the risk.

Losartan passes into breast milk and may cause the baby to have low blood pressure. Your doctor may prescribe an alternative medicine while breastfeeding.

What medicines interact with Losartan?

  • Pain medication called Nonsteroidal anti-inflammatory drugs (NSAIDs) when used together with losartan may affect your kidneys. Examples of NSAIDs include naproxen, ibuprofen, celecoxib, diclofenac, etoricoxib
  • Other medicines used to treat blood pressure.
  • Aspirin (if you are taking more than 3g a day).
  • Potassium supplements or salt substitutes which contain potassium.
  • Heparin which is a medicine that thins your blood.
  • Water tablets called diuretics.
  • Lithium which is used to treat some mental health problems.
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