Sounds like ' low-SAR-tan'

Losartan is used to treat high blood pressure and heart failure. It also helps protects the kidneys in people with diabetic kidney disease. Find out how to take it safely and the possible side effects. Losartan is also called Cozaar.

Type of medicine Also called
  • Belongs to a group of medicines called angiotensin receptor blockers (ARBs)
  • Losartan Actavis®
  • Cozaar®

What is losartan?

Losartan has many different effects on the body and is used to treat a variety of conditions. It belongs to a group of medicines called ARBs. Losartan may be used for:

  • High blood pressure (hypertension) by relaxing the blood vessels and lowering your blood pressure.
  • Heart failure to help your heart pump blood more easily. This can help to relieve symptoms such as shortness of breath and swelling of feet, legs and abdomen. It can also help prevent strokes and heart attacks.
  • Diabetic kidney disease (diabetic nephropathy) to protect your kidneys and help them to function.


In Aotearoa New Zealand losartan is available as tablets, which come in different strengths: 12.5 mg, 25 mg, 50 mg and 100 mg. Losartan is also available as a combination tablet with hydrochlorothiazide. For more information see losartan plus hydrochlorothiazide. 

  • The dose of losartan will be different for different people. Your dose of losartan will depend on what it is being used for. Your doctor will tell you the dose that is right for you.
  • Your doctor will usually start you on a low dose and increase the dose depending on how you respond. This allows your body to get used to the medicine and reduces side effects.
  • Always take your losartan exactly as your doctor has told you. The pharmacy label on your medicine will tell you how much losartan to take, how often to take it, and any special instructions.

How to take losartan

  • Timing: Take your dose at about the same time each day. You can take losartan with or without food.
  • Stay hydrated and make sure you drink enough water. This is especially important during exercise and hot weather, which can increase your risk of dehydration. If you do not drink enough water you may feel faint, light-headed or sick. 
  • Limit alcohol while taking losartan. Having the occasional drink while you are taking losartan is safe. However, regularly drinking excessive amounts increase your chance of side effects and reduce the effects of losartan.
  • Missed dose: If you forget to take your dose, take it as soon as you remember that day. But if it is nearly time for your next dose, just take the next dose at the right time. Do not take double the dose.

Cautions while you are taking losartan

Be careful when taking pain relief medicines

Check with your healthcare provider before taking anti-inflammatory pain relief medication such as ibuprofen, while you are taking losartan. This combination can be very harmful to your kidneys and can cause acute kidney injury. You have a higher risk of harming your kidneys if you are taking diuretics (water pills), if you are elderly or if you are dehydrated. Ask your doctor or pharmacist for a safer pain relief options. Read more about NSAIDs and protecting your kidneys.

Examples of NSAIDs
  • Ibuprofen (Ibugesic, I-Profen, Nurofen)
  • Diclofenac (Voltaren)
  • Naproxen (Noflam, Naprosyn)
  • Mefenamic acid (Ponstan)
  • Celecoxib (Celebrex)

Have a sick day plan

If you have diarrhoea and/or vomiting from a stomach bug, or have dehydration from other causes, it’s important to let your doctor know. They may advise you to stop taking losartan for a few days and restart when you feel better. The reason for this is that this medicine can increase the level of potassium salts in your blood, particularly if you are dehydrated.

Pregnant or planning a pregnancy

Do not take losartan if you are pregnant, or if there is a chance you could become pregnant. Losartan can cause birth defects and is harmful to unborn babies. Talk to your healthcare provider about alternative blood pressure medicines.

Losartan and other medicines or supplements

Losartan can interact with some medications, herbal supplements and rongoā Māori, so check with your doctor or pharmacist before starting losartan and before starting any new products.

What are the side effects of losartan?

Like all medicines, losartan can cause side effects, although not everyone gets them. Often side effects improve as your body gets used to the new medicine.

Side effects What should I do?
  • Dizziness
  • Feeling lightheaded
  • Feeling faint when you stand up
  • This is quite common when you first start taking losartan and usually goes away with time.
  • Be careful when getting up from either lying down or sitting to avoid falls. These effects put you at risk of falls and injuries, especially if you are an older person.
  • Stand up slowly. If you do feel dizzy, sit-down or lie down for a few moments.
  • Avoid alcohol.
  • Tell your doctor if this continues.
  • Muscle cramps
  • Muscle weakness
  • This is less common and may be a sign of rising potassium levels.
  • Tell your doctor – you may need a blood test to check the amount of potassium in your blood.
  • Allergic reaction such as skin rash, itching, swelling of the lips, face, and mouth or difficulty breathing such as chest tightness, or wheezing
  • Allergic reactions are rare but serious.
  • Tell your doctor immediately or ring Healthline 0800 611 116.
  • Signs of problems with your liver such as yellowing of the skin or eyes, dark urine, pain in the abdomen
  • Liver problems are rare but serious.
  • Tell your doctor immediately or ring Healthline 0800 611 116.

Did you know that you can report a side effect to a medicine to CARM (Centre for Adverse Reactions Monitoring)? Report a side effect to a product.

Learn more

The following links have more information on losartan:


  1. Losartan NZ Formulary, NZ

Additional resources for healthcare professionals

Losartan actavis Medsafe, NZ
Medicines and hyperkalaemia Medsafe, NZ, 2015
Hypertension in adults – the silent killer BPAC, NZ, 2013
Managing patients with heart failure in primary care BPAC, NZ, 2013

Credits: Sandra Ponen, Pharmacist. Reviewed By: Maya Patel, MPharm PGDipClinPharm, Auckland Last reviewed: 02 Apr 2022