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1. About losartan

Losartan is a medicine widely used to treat high blood pressure and heart failure, and to protect your kidneys if you have both kidney disease and diabetes.

Losartan helps to prevent future strokes, heart attacks and kidney problems.

It also improves your survival if you're taking it for heart failure or after a heart attack.

This medicine is only available on prescription. It comes as tablets.

2. Key facts

  • Losartan lowers your blood pressure and makes it easier for your heart to pump blood around your body.
  • It's often used as a second-choice treatment if you had to stop taking another blood pressure-lowering medicine because it gave you a dry, irritating cough.
  • If you have diarrhoea and vomiting from a stomach bug or illness while taking losartan, tell your doctor. You may need to stop taking it until you feel better.
  • The main side effects of losartan are dizziness and fatigue, but they're usually mild and shortlived.
  • Losartan is not normally recommended in pregnancy or while breastfeeding. Talk to your doctor if you're trying to get pregnant, you're already pregnant or you're breastfeeding.
  • Losartan is also called by the brand name Cozaar.

3. Who can and can't take losartan

Losartan can be taken by adults aged 18 years and over.

Children aged 6 years and older can take it, but only to treat high blood pressure.

Your doctor may prescribe losartan if you've tried taking similar blood pressure-lowering medicines such as ramipril and lisinopril in the past, but had to stop taking them because of side effects such as a dry, irritating cough.

Losartan isn't suitable for some people.

To make sure losartan is safe for you, tell your doctor if you:

4. How and when to take it

Take losartan tablets once a day.

Your doctor may suggest that you take your first dose before bedtime, because it can make you dizzy. After the very first dose, you can take losartan at any time of day. Try to take it at the same time every day.

You can take losartan tablets with or without food. Swallow the tablets with a drink of water.

How much will I take?

The dose of losartan you take depends on why you need the medicine. Take it as instructed by your doctor.

Usually, adults take:

  • 50mg to 100mg once a day to treat high blood pressure and to protect their kidneys
  • 12.5mg to 150mg once a day for heart failure

The dose may be lower if you've recently lost body fluids (for example, because of diarrhoea or being sick) or you're over the age of 75.

If your child needs losartan, your doctor will usually use your child's weight to work out the right dose.

Will my dose go up or down?

After a few weeks your doctor will check your blood pressure and ask you if you're getting any side effects. You may also have blood tests to check how well your kidneys are working and the amount of potassium in your blood. Your doctor will then decide whether to change your dose of losartan.

If losartan doesn't bring your blood pressure down, your doctor may want to increase the dose. If your blood pressure gets too low or you get side effects, your doctor may want to lower your dose.


Take losartan even if you feel well, as you will still be getting the benefits of the medicine.

What if I get sick while I'm taking it?

If you get severe diarrhoea or vomiting for any reason, contact your doctor or a pharmacist. They’ll be able to advise you about what to do.

They may recommend that you stop taking losartan until you’re better, and you’re able to eat and drink normally again.

What if I forget to take it?

If you miss a dose of losartan, take it as soon as you remember. Do not take a double dose to make up for a forgotten one.

If you often forget doses, it may help to set an alarm to remind you. You could also ask your pharmacist for advice on other ways of helping you remember your medicine.

What if I take too much?

If you take too many losartan tablets by accident, contact your doctor or go to your nearest hospital A&E department straight away.

An overdose of losartan can cause dizziness, sleepiness and a pounding heartbeat.

The amount of losartan that can lead to an overdose varies from person to person.

Urgent advice: Call a doctor or go to A&E as soon as possible if you take too much losartan

If you need to go to your nearest hospital A&E department, do not drive yourself - get someone else to drive you or call for an ambulance.

Take the losartan packet or leaflet inside it plus any remaining medicine with you.

5. Side effects

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

Common side effects

These common side effects happen in more than 1 in 100 people:

  • feeling dizzy or having a spinning sensation (vertigo)
  • headaches
  • feeling sick (nausea)
  • being sick (vomiting) or diarrhoea
  • pain in your joints or muscles

Talk to your doctor or pharmacist if these side effects bother you or don't go away.

Serious side effects

It happens rarely, but some people have serious side effects after taking losartan.

Call a doctor straight away if you have:

  • yellow skin or the whites of your eyes turn yellow - this can be a sign of liver problems
  • severe stomach pain - this can be a sign of an inflamed pancreas
  • pale skin, feeling tired, faint or dizzy, purple spots, any sign of bleeding, sore throat and fever - these can be signs of blood or bone marrow disorder
  • weakness, an irregular heartbeat, pins and needles and muscle cramps - these can be signs of changes in the sodium and potassium levels in your blood

Serious allergic reaction

In rare cases, losartan may cause a serious allergic reaction (anaphylaxis).

Urgent advice: Contact a doctor straight away if:

  • you get a skin rash that may include itchy, red, swollen, blistered or peeling skin
  • you're wheezing
  • you get tightness in the chest or throat
  • you have trouble breathing or talking
  • your mouth, face, lips, tongue or throat start swelling

These are warning signs of a serious allergic reaction. A serious allergic reaction is an emergency.

These are not all the side effects of losartan. For a full list, see the leaflet inside your medicines packet.


You can report any suspected side effect to the UK safety scheme.

6. How to cope with side effects

What to do about:

  • feeling dizzy - if losartan makes you feel dizzy when you stand up, try getting up very slowly or stay sitting down until you feel better. If you begin to feel dizzy, lie down so that you don't faint, then sit until you feel better. Do not drive or use tools or machines if you feel dizzy, have muscle cramps or muscle pain, or if you just feel a bit shaky.
  • headaches - make sure you rest and drink plenty of fluids. Do not drink too much alcohol. Ask your pharmacist to recommend a painkiller. Headaches should usually go away after the first week of taking losartan. Talk to your doctor if they last longer than a week or are severe.
  • feeling sick (nausea) - try taking your tablets with or after a meal or snack. It may also help if you don't eat rich or spicy food.
  • being sick (vomiting) or diarrhoea - drink plenty of fluids, such as water or squash, to prevent dehydration - if you're being sick, take small, frequent sips. Speak to a pharmacist if you have signs of dehydration, such as peeing less than usual or having dark, strong-smelling pee. If you get severe diarrhoea or vomiting from a stomach bug or illness, tell your doctor. You may need to stop taking losartan for a while until you feel better.
  • pain in your joints or muscles - if you get unusual muscle pain, weakness or tiredness which isn't from exercise or hard work, talk to your doctor. You may need a blood test to check what might be causing it.

7. Pregnancy and breastfeeding

Losartan is not normally recommended in pregnancy or when breastfeeding. However, your doctor may prescribe it if they think the benefits of the medicine outweigh the risks.

If you're trying to get pregnant or you're already pregnant, talk to your doctor about the benefits and possible harms of taking losartan. These will depend on how many weeks pregnant you are and the reason you need to take it. There may be other treatments that are safer for you.

For more information about how losartan can affect you and your baby during pregnancy, visit the Best Use of Medicines in Pregnancy (BUMPS) website.

Losartan and breastfeeding

Small amounts of losartan may get into breast milk. This can cause low blood pressure in the baby. Talk to your doctor, as other medicines might be better while you are breastfeeding.

Non-urgent advice: Tell your doctor if you're:

  • trying to get pregnant
  • pregnant
  • breastfeeding

8. Cautions with other medicines

Some medicines interfere with the way losartan works.

Tell your doctor if you're taking:

  • other medicines to help lower your blood pressure, including aliskiren, enalapril, captopril, lisinopril or ramipril
  • painkillers such as ibuprofen, naproxen, diclofenac, celecoxib or etoricoxib
  • aspirin (if you are taking more than 3g a day)
  • potassium supplements or salt substitutes which contain potassium
  • heparin (a blood thinning medicine)
  • tablets which make you pee more (diuretics)
  • lithium (a medicine for mental health problems)
  • spironolactone (a medicine to treat heart failure)

Mixing losartan with herbal remedies or supplements

There's very little information about taking herbal remedies and supplements with losartan.


For safety, tell your doctor or pharmacist if you're taking any other medicines, including herbal remedies, vitamins or supplements.

9. Common questions

How does losartan work?

Losartan is a type of blood pressure-lowering medicine called an angiotensin receptor blocker.

Like other angiotensin receptor blockers, losartan relaxes and widens your blood vessels. This lowers your blood pressure and makes it easier for your heart to pump blood around your body.

In diabetic kidney disease, it helps to protect your kidneys and slows down the disease. It does this by reducing the amount of protein you lose through your kidneys and by reducing high blood pressure.

How long does losartan take to work?

Losartan starts to reduce high blood pressure after about 6 hours but it may take 3 to 6 weeks to fully take effect.

If you have high blood pressure, you may not have any symptoms. In this case, you may not feel any different when you take losartan. This doesn't mean that the medicine isn't working, and it's important to keep taking it.

How long will I take it for?

Usually, treatment with losartan is long term, and you may have to take it for the rest of your life.

Is it safe to take for a long time?

Losartan is generally safe to take for a long time. In fact, it works best when you take it for a long time.

However taking losartan for a long time can sometimes cause your kidneys not to work as well as they should. Your doctor will check how well your kidneys are working with regular blood tests.

What will happen if I stop taking it?

Talk to your doctor if you want to stop taking losartan.

Stopping losartan may cause your blood pressure to rise - and this can increase your chances of having a heart attack or stroke.

If you're bothered by side effects, your doctor may be able to prescribe you a different blood pressure-lowering medicine.

Can I come off losartan now my blood pressure is lower?

Even if your blood pressure is successfully lowered by losartan, it's best to carry on taking it. If you stop taking losartan, your blood pressure could rise back up again.

If you need blood pressure-lowering medicines, you'll probably need to take them for the rest of your life.

Remember, by keeping your blood pressure low, you're protecting yourself against having a heart attack or stroke in the future.

Can taking sartans increase the risk of getting cancer?

In July 2018, the European Medicines Agency (EMA) recalled some packs of valsartan produced by a manufacturer in China. Some samples contained traces of a chemical (NDMA). NDMA may be linked to a very small increased risk of developing cancer.

Since then the EMA have also found traces of a similar chemical (NDEA) in batches of losartan, irbesartan and valsartan. They have recalled any affected batches from the manufacturers while they investigate further.

In the meantime the EMA advise that there’s no immediate risk to patients. It’s important to continue your treatment for high blood pressure and you should keep taking your medicine as usual.

If you have any worries or concerns about the medicine that you’re taking, speak to your doctor or pharmacist.

Can I drink alcohol with losartan?

Drinking alcohol can increase the blood pressure-lowering effect of losartan, which can make you feel dizzy or light-headed.

During the first few days of taking losartan or after a dose increase, it is best to stop drinking alcohol until you see how the medicine affects you.

If you find losartan makes you feel dizzy it's best to stop drinking alcohol.

Is there any food or drink I should avoid?

Do not use salt substitutes such as Lo-Salt. This is because they are high in potassium. When mixed with losartan they may make the level of potassium in your blood too high.

There's nothing else you need to avoid while taking losartan. Eating a healthy, balanced diet can help if you have high blood pressure.

Are there similar medicines to losartan?

There are several other angiotensin receptor blockers that work in the same way as losartan. They include candesartan, irbesartan and valsartan.

There are other types of blood pressure-lowering medicines:

  • calcium channel blockers - for example amlodipine
  • angiotensin converting enzyme (ACE) inhibitors - for example ramipril
  • beta blockers - for example bisoprolol
  • tablets which make you pee more (diuretics) - for example bendroflumethiazide

The blood pressure-lowering medicine you're prescribed depends on your age and ethnicity:

  • if you're under 55 - you'll usually be offered an ACE inhibitor or an angiotensin receptor blocker
  • if you're 55 or older, or you're any age and of African Caribbean or black African origin - you'll usually be offered a calcium channel blocker

Many people need to take a combination of different blood pressure-lowering medicines.

What are the differences between losartan and other medicines for high blood pressure?

Losartan works as well as other angiotensin receptor blockers when it's used to lower blood pressure. Its side effects are also similar.

It also works as well as ramipril and other angiotensin converting enzyme (ACE) inhibitors to lower blood pressure.

Losartan can be taken by people who have tried ramipril or other ACE inhibitors but had to stop taking them because of side effects such as a dry, irritating cough.

Can I take losartan before surgery?

If you're going to be put to sleep for an operation using a general anaesthetic, tell your doctor that you're taking losartan.

Losartan can reduce your blood pressure when it's used with general anaesthetics.

Your doctor will probably advise you to stop taking losartan 24 hours before surgery.

Can I take losartan for migraines?

There's some evidence that losartan might help prevent migraines.

However, losartan is not officially approved for migraine. Your doctor will probably advise you to try other medicines first.

Can I take losartan for Raynaud's phenomenon?

At present, medicines like nifedipine are used first for Raynaud's phenomenon. But if your condition doesn't improve, your doctor might try losartan.

Can I take losartan to protect myself against Alzheimer's disease?

There have been some studies which have looked at whether blood pressure medicines could help protect people against Alzheimer's. However, at the moment, there is not enough evidence to recommend taking losartan or other similar medicines for Alzheimer's.

There are steps you can take that may reduce your risk of Alzheimer's. If you are worried about getting Alzheimer's disease in the future or have a family history of this condition, speak to your doctor.

Is losartan addictive?

No, there's no evidence that losartan is addictive.

Will it affect my sex life?

Losartan won't affect your sex life.

Will it affect my fertility?

There's no firm evidence to suggest that taking losartan will reduce fertility in either men or women.

However, if you're trying to get pregnant, talk to your doctor first. This medicine is usually not recommended in pregnancy.

Will it affect my contraception?

Losartan won't affect any type of contraception.

However, some types of hormonal methods of contraception, such as the combined contraceptive pill and contraceptive patch, aren't usually recommended for women with high blood pressure. Talk to your doctor if you're taking a combined hormonal contraceptive.

Can I drive or ride a bike?

Losartan can make you feel dizzy - especially when you first start taking it or after taking a bigger dose. If this happens to you, do not drive a car, ride a bike, or use tools or machinery until you feel better.

Can lifestyle changes help?

You can boost the health of your heart by making some key lifestyle changes. These will also help if you have high blood pressure or heart failure.

  • Quit smoking - smoking increases your heart rate and blood pressure. Quitting smoking brings down your blood pressure and relieves heart failure symptoms. Try to avoid secondhand smoke too.
  • Cut down on alcohol - drinking too much alcohol raises blood pressure over time. It makes heart failure worse too. Try to keep to the recommended guidelines of no more than 14 units of alcohol a week. A standard glass of wine (175ml) is 2 units. A pint of lager or beer is usually 2 to 3 units of alcohol.
  • Exercise - regular exercise lowers blood pressure by keeping your heart and blood vessels in good condition. It doesn't need to be too energetic - walking every day will help.
  • Eat well - aim to eat a diet that includes plenty of fruit and veg, wholegrains, fat-free or low-fat dairy products and lean proteins. It's a good idea to cut down on salt too. Eating too much salt is the biggest cause of high blood pressure - the more salt you eat, the higher your blood pressure will be. Aim for no more than 6g of salt a day.
  • Deal with stress - when you're anxious or upset, your heart beats faster, you breathe more heavily and your blood pressure often goes up. This can also make heart failure worse. Find ways to reduce stress in your life. To give your heart a rest, try napping or putting your feet up when possible. Spend time with friends and family to be social and help keep stress at bay.
  • Vaccinations - if you have heart failure, you should have a flu jab every year and a pneumonia vaccination every 5 years. Ask your doctor about these vaccinations. You can have them free on the NHS.

Page last reviewed: 13 December 2018
Next review due: 13 December 2021