Sounds like ' low-SAR-tan'

Losartan is used to treat high blood pressure and heart failure and to prevent kidney problems in people with diabetes. Find out how to take it safely and 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
  • diabetic kidney disease (diabetic nephropathy) to protect your kidneys and help them to function.

Losartan can work quickly for high blood pressure (hypertension). If you have heart failure it may be a few weeks before you notice an improvement in your symptoms. Once you have started losartan you will generally keep taking it for life unless you have a side effect. In New Zealand losartan is available as tablets.


Losartan tablets come in different strengths: 12.5 mg, 25 mg, 50 mg and 100 mg.

  • The dose of losartan will be different for different people. Your doctor will tell you the dose that is right for you. Your dose of losartan will depend on what it is being used for.
  • 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 unwanted side effects.
  • Losartan is usually taken once a day.
  • 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.
  • Losartan tablets are available in different strengths. If your tablets look different to your last supply speak with your doctor or pharmacist for advice.

How to take losartan

  • Timing: Take losartan, once a day, at the same time each day. It is best taken in the morning. You can take losartan with or without food.
  • Limit drinking alcohol while you are taking losartan. Alcohol can increase your chance of side effects such as dizziness and lightheadedness.
  • 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..

Precautions – before taking losartan

  • Are you pregnant or planning a pregnancy?
  • Are you breastfeeding?
  • Do you have problems with your kidneys or liver?
  • Have you ever had an allergic reaction with swelling of your lips, eyes or tongue (called angioedema)?
  • Are you are taking or using any other medicines? This includes any medicines you are using which are available to buy from a pharmacy, supermarket or natural health store without a prescription.

If so, it’s important that you tell your doctor or pharmacist before you start taking losartan. Sometimes a medicine isn’t suitable for a person with certain conditions, or it can only be used with extra care.

Cautions while you are taking losartan

Have a sick day plan

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

Be careful when taking some pain relief medicines

Losartan help to protect your kidneys from damage if you have diabetes. In most cases losartan is protective but if you are taking losartan and diuretics (water pills), the combination of these with NSAIDs (anti-inflammatory pain relief medication) can be very harmful to your kidneys. It can cause acute kidney injury. This combination is called the dangerous trio or triple whammy. You have a higher risk of harm to your kidneys if you are also elderly or are dehydrated. 

If you are taking losartan with a diuretic, do not use NSAIDs for pain relief. Ask your doctor or pharmacist for a safer option. Read more about NSAIDs and protecting your kidneys.

Examples of diuretics Examples of NSAIDs
  • bendroflumethiazide (Arrow-Bendrofluazide)
  • chlorthalidone (Hygroton)
  • indapamide (Dapa-Tabs, Napamide)
  • metolazone (Zaroxolyn)
  • furosemide (Diurin)
  • ibuprofen (Ibugesic, I-Profen, Nurofen)
  • diclofenac (Voltaren)
  • naproxen (Noflam, Naprosyn)
  • mefenamic acid (Ponstan)
  • celecoxib (Celebrex)

Side effects

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 elderly.
  • 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
  • Changes in your heartbeateat (either fast, slow or irregular)
  • Tell your doctor.
  • Allergic reaction such as skin rash, itching, swelling of the lips, face, and mouth or difficulty breathing such as chest tightness, or wheezing
  • 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
  • Tell your doctor immediately or ring HealthLine 0800 611 116


  • Losartan may interact with a few medications and herbal supplements so check with your doctor or pharmacist before starting losartan or before starting any new medicines.
  • Also, check with your pharmacist before taking over-the-counter medicines such as anti-inflammatories such as diclofenac (e.g. Voltaren Rapid), ibuprofen (e.g. Nurofen), naproxen (e.g. Naprogesic).

Learn more

The following links have more information on losartan:

New Zealand Formulary Patient Information: losartan


  1. Losartan New Zealand Formulary
Credits: Sandra Ponen, Pharmacist. Reviewed By: Angela Lambie, Pharmacist, Auckland Last reviewed: 15 Nov 2018