1. Losartan oral tablet is available as a brand-name drug and a generic drug. Brand name: Cozaar.
  2. Losartan comes only as a tablet you take by mouth.
  3. Losartan is used to treat hypertension (high blood pressure). It’s also used to help your kidneys work better if you have diabetes. In addition, it’s used to reduce your risk of a stroke if you have high blood pressure and the heart condition called left ventricular hypertrophy.

FDA warning: Use during pregnancy

  • This drug has a black box warning. This is the most serious warning from the Food and Drug Administration (FDA). A black box warning alerts doctors and patients about drug effects that may be dangerous.
  • You shouldn’t take this drug if you’re pregnant or planning to become pregnant. Losartan can harm or end your pregnancy. If you become pregnant, stop taking this medication right away and call your doctor.

Losartan is a prescription drug. It comes as an oral tablet.

Losartan is available as the brand-name drug Cozaar. It’s also available as a generic drug. Generic drugs usually cost less than the brand-name version. In some cases, they may not be available in every strength or form as the brand-name drug.

Losartan may be taken as part of a combination therapy with other medications to lower your blood pressure.

Losartan is used for three main purposes. It’s used to:

  • treat high blood pressure
  • reduce your risk of a stroke if you have high blood pressure and left ventricular hypertrophy (LVH), a condition that causes the walls in the heart’s left ventricle to thicken
  • treat diabetic nephropathy, which is kidney disease caused by diabetes

Losartan belongs to a class of drugs called angiotensin receptor blockers (ARBs). A class of drugs is a group of medications that work in a similar way. They’re often used to treat similar conditions. Other ARBs include olmesartan, valsartan, and telmisartan. Like losartan, these drugs can be used to treat high blood pressure.

Losartan works by blocking the action of angiotensin II, a chemical in your body that causes your blood vessels to tighten and narrow. Losartan helps relax and widen your blood vessels. This lowers your blood pressure. This helps treat high blood pressure as well as the other two conditions losartan is usually prescribed for.

High blood pressure and LVH increase your risk of stroke, so lower blood pressure reduces your risk. Lower blood pressure also reduces your risk of kidney damage. This is because high blood pressure raises your risk of kidney damage that’s caused by the high blood sugar levels linked with diabetes.

Losartan doesn’t cause drowsiness, but it can cause other side effects.

More common side effects

The more common side effects that can occur with losartan include:

  • upper respiratory infections, such as the common cold
  • dizziness
  • stuffy nose
  • back pain
  • diarrhea
  • fatigue
  • low blood sugar
  • chest pain
  • high or low blood pressure

If these effects are mild, they may go away within a few days or a couple of weeks. If they’re more severe or don’t go away, talk to your doctor or pharmacist.

Serious side effects

Call your doctor right away if you have serious side effects. Call 911 if your symptoms feel life-threatening or if you think you’re having a medical emergency. Serious side effects and their symptoms can include the following:

  • High potassium blood levels. Symptoms can include:
    • heart rhythm problems
    • muscle weakness
    • slow heart rate
  • Allergic reactions. Symptoms can include:
    • swelling of your face, lips, throat, or tongue
  • Low blood pressure. Symptoms can include:
    • feeling faint or dizzy
  • Kidney disease. Symptoms can include:
    • swelling in your feet, ankles, or hands
    • unexplained weight gain

Disclaimer: Our goal is to provide you with the most relevant and current information. However, because drugs affect each person differently, we can not guarantee that this information includes all possible side effects. This information is not a substitute for medical advice. Always discuss possible side effects with a healthcare provider who knows your medical history.

Losartan oral tablet can interact with other medications, vitamins, or herbs you may be taking. An interaction is when a substance changes the way a drug works. This can be harmful or prevent the drug from working well.

To help avoid interactions, your doctor should manage all of your medications carefully. Be sure to tell your doctor about all medications, vitamins, or herbs you’re taking. To find out how this drug might interact with something else you’re taking, talk to your doctor or pharmacist.

Examples of drugs that can cause interactions with losartan are listed below.

Bipolar disorder drug

Taking lithium with losartan may increase the levels of lithium in your body. This effect can be dangerous.

Blood pressure drugs

Taking losartan with other medications that lower your blood pressure and work on your renin-angiotensin system has risks. Taking these drugs together raises your risk of high blood potassium levels, kidney damage, and low blood pressure. An example of these drugs is:

  • aliskiren

Nonsteroidal anti-inflammatory drugs (NSAIDs)

Using losartan with NSAIDs raises your risk of kidney damage. Your risk may be higher if you have poor kidney function, are a senior, take a water pill, or are dehydrated. NSAIDs may also reduce the blood pressure-lowering effects of losartan. This means that losartan may not work as well if you take it with an NSAID.

Examples of NSAIDs include:

  • naproxen
  • ibuprofen

Tuberculosis drug

Taking rifampin with losartan can increase how quickly your body removes losartan. This means that losartan may not work as well to lower your blood pressure if you take it with these drugs.

Diuretics (water pills)

Losartan can cause low blood pressure. Your risk of low blood pressure is increased if you also take diuretics. Symptoms of low blood pressure can include dizziness or feeling faint, or chest pain. Examples of diuretics include:

  • hydrochlorothiazide
  • furosemide
  • spironolactone

Drugs that contain potassium

Losartan can increase the levels of a substance called potassium in your blood. Taking losartan with drugs that contain potassium, or salt substitutes with potassium, can increase your risk of hyperkalemia (high levels of potassium).

Examples of these drugs include:

  • potassium chloride (Klor-Con, Klor Con M, K-Tab, Micro-K)
  • potassium gluconate
  • potassium bicarbonate (Klor-Con EF)

Disclaimer: Our goal is to provide you with the most relevant and current information. However, because drugs interact differently in each person, we can not guarantee that this information includes all possible interactions. This information is not a substitute for medical advice. Always speak with your healthcare provider about possible interactions with all prescription drugs, vitamins, herbs and supplements, and over-the-counter drugs that you are taking.

This drug comes with several warnings.

Allergy warning

Losartan can cause a severe allergic reaction. Symptoms include:

  • trouble breathing
  • swelling of your throat or tongue
  • hives

If you develop these symptoms, call 911 or go to the nearest emergency room.

Don’t take this drug again if you’ve ever had an allergic reaction to it. Taking it again could be fatal (cause death).

Alcohol interaction warning

Using drinks that contain alcohol while taking losartan can cause a sedative effect. This means you may have slowed reflexes, poor judgment, and sleepiness. This can be dangerous if you drive or use other machinery. Alcohol can also increase the blood-pressure lowering effect of losartan. This increases the chance of your blood pressure getting too low.

Low blood pressure warning

This drug may cause low blood pressure, which can make you to feel faint or dizzy. If this happens, lie down and call your doctor right away.

Warnings for people with certain health conditions

For people with an active renin-angiotensin system: Tell your doctor if you have heart failure, low blood pressure, or renal artery stenosis (narrowing of the arteries that carry blood to your kidneys). With these conditions, your kidneys depend on the renin-angiotensin system. Taking this drug can also activate this system. If you take losartan when your renin-angiotensin system is activated, you can damage your kidneys.

For people with kidney problems: This medication can make kidney disease worse. Symptoms of worsening kidney disease include:

  • swelling in your hands, feet, or ankles
  • unexplained weight gain

Warnings for other groups

For pregnant women: Losartan is a category D pregnancy drug. That means two things:

  1. Studies show a risk of adverse effects to the fetus when the mother takes the drug.
  2. The benefits of taking the drug during pregnancy may outweigh the potential risks in certain cases.

This drug can harm or end your pregnancy. Tell your doctor if you’re pregnant or plan to become pregnant. Losartan should be used during pregnancy only if the potential benefit justifies the potential risk.

For women who are breastfeeding: It isn’t known if losartan passes into breast milk. If it does, it may cause side effects in a child who is breastfed. Talk to your doctor if you breastfeed your child. You may need to decide whether to stop breastfeeding or stop taking this medication.

For seniors: Older adults may process drugs more slowly. A typical adult dosage may cause levels of this drug to be higher than normal. If you’re a senior, you may need a lower dosage or a different treatment schedule.

For children: This medication should not be used in children younger than 6 years.

All possible dosages and forms may not be included here. Your doctor will tell you what dosage is right for you. Your dose, form, and how often you take it will depend on:

  • your age
  • the condition being treated
  • how severe your condition is
  • other medical conditions you have
  • how you react to the first dose

What are you taking this medication for?

The dosage information below is for the conditions that losartan is most often prescribed to treat. This list may not contain all conditions that your doctor can prescribe this drug for. If you have questions about your prescription, talk with your doctor.

Drug forms and strengths

Generic: Losartan

  • Form: oral tablet
  • Strengths: 25 mg, 50 mg, 100 mg

Brand: Cozaar

  • Form: oral tablet
  • Strengths: 25 mg, 50 mg, 100 mg

Dosage for high blood pressure (hypertension)

Adult dosage (ages 18–64 years)

The typical starting dosage is 50 mg once daily. Dosages range between 25 and 100 mg per day. You take losartan once or twice per day.

Child dosage (ages 6–17 years)

The dosage is based on your child’s weight. The usual dosage is around 0.7 mg/kg of body weight taken once per day. Your child’s doctor will increase or decrease the dosage depending on your child’s response to the medication.

Child dosage (ages 0–5 years)

This drug should not be used in children younger than 6 years.

Senior dosage (ages 65 years and older)

There are no specific recommendations for senior dosage. Older adults may process drugs more slowly. If you’re a senior, you may need a lower dosage or a different schedule. A normal adult dosage may cause levels of this drug to be higher than normal in your body.

Dosage for diabetic nephropathy

Adult dosage (ages 18–64 years)

The typical starting dosage is 50 mg once daily. Your doctor may increase your dosage to 100 mg per day if needed. You take losartan once or twice per day.

Child dosage (ages 6–17 years)

The dosage is based on your child’s weight. The usual dosage is around 0.7 mg/kg of body weight taken once per day. Your child’s doctor will increase or decrease the dosage depending on your child’s response to the medication.

Child dosage (ages 0–5 years)

This drug should not be used in children younger than 6 years.

Senior dosage (ages 65 years and older)

There are no specific recommendations for senior dosage. Older adults may process drugs more slowly. If you’re a senior, you may need a lower dosage or a different schedule. A normal adult dosage may cause levels of this drug to be higher than normal in your body.

Dosage to reduce stroke risk in people with high blood pressure and left ventricular hypertrophy

Adult dosage (ages 18–64 years)

The typical dosage is 50 mg taken once daily. Your doctor may increase your dosage to 100 mg per day if needed.

Child dosage (ages 0–17 years)

This drug should not be used in children younger than 17 years for this condition.

Senior dosage (ages 65 years and older)

There are no specific recommendations for senior dosage. Older adults may process drugs more slowly. If you’re a senior, you may need a lower dosage or a different schedule. A normal adult dosage may cause levels of this drug to be higher than normal in your body.

Special dosage considerations

For people with liver problems: If you have mild-to-moderate liver problems, your doctor may lower your starting dosage to 25 mg per day.

Disclaimer: Our goal is to provide you with the most relevant and current information. However, because drugs affect each person differently, we can not guarantee that this list includes all possible dosages. This information is not a substitute for medical advice. Always speak with your doctor or pharmacist about dosages that are right for you.

Losartan is used for long-term treatment. It comes with serious risks if you don’t take it as prescribed.

If you don't take it at all: Losartan lowers high blood pressure. If you don’t take it, your blood pressure will stay high. This will increase your risk of a stroke or heart attack.

If you don't take it on schedule: Your blood pressure may not improve or may get worse. You may increase your risk of a heart attack or stroke.

What to do if you miss a dose: If you forget to take your dose, take it as soon as you remember. If it’s just a few hours until the time for your next dose, wait and only take one dose at that time. Never try to catch up by taking two doses at once. This could cause dangerous side effects.

If you take too much: If you take too much losartan, you may have these symptoms:

  • feeling like your heart is pounding
  • weakness
  • dizziness

If you think you’ve taken too much losartan, call your doctor or local poison control center. If your symptoms are severe, call 911 or go to the nearest emergency room right away.

How to tell if the drug is working: Your blood pressure should be lower. Your doctor will monitor your blood pressure at your checkups. You can also check your blood pressure at home.

You may not be able to tell if this drug is helping your kidney function or reducing your risk of stroke. That doesn’t mean that the drug isn’t working. Keep taking this drug unless your doctor tells you to stop.

Keep these considerations in mind if your doctor prescribes losartan for you.

General

You can cut or crush losartan tablets.

Storage

  • Store losartan at room temperature between 59°Fand 86°F(15°C and 30°C).
  • Don’t freeze this drug.
  • Keep this medication away from light.
  • Don’t store this medication in moist or damp areas, such as bathrooms.

Refills

A prescription for this medication is refillable. You should not need a new prescription for this medication to be refilled. Your doctor will write the number of refills authorized on your prescription.

Travel

When traveling with your medication:

  • Always carry your medication with you. When flying, never put it into a checked bag. Keep it in your carry-on bag.
  • Don’t worry about airport x-ray machines. They can’t harm your medication.
  • You may need to show airport staff the pharmacy label for your medication. Always carry the original prescription-labeled container with you.
  • Don’t put this medication in your car’s glove compartment or leave it in the car. Be sure to avoid doing this when the weather is very hot or very cold.

Self-management

You may need to check your blood pressure at home. To do this, you may need to buy a home blood pressure monitor. You should keep a log with the date, the time of day, and your blood pressure readings. Bring this log with you to your doctor appointments.

Clinical monitoring

During treatment with losartan, your doctor may check your:

  • blood cell levels
  • potassium levels
  • kidney function
  • blood pressure

Hidden costs

You may need to buy a blood pressure monitor to check your blood pressure at home. These monitors are available at most pharmacies.

Are there any alternatives?

There are other drugs available to treat your condition. Some may be better suited for you than others. Talk to your doctor about other options that may work for you.

Do not stop taking losartan without talking to your doctor. Stopping it suddenly can cause your blood pressure to increase quickly. This raises your risk of a heart attack or stroke. If you want to stop taking losartan, talk with your doctor. They will slowly taper your dosage so that you can stop using the drug safely.

Disclaimer: Healthline has made every effort to make certain that all information is factually correct, comprehensive, and up-to-date. However, this article should not be used as a substitute for the knowledge and expertise of a licensed healthcare professional. You should always consult your doctor or healthcare professional before taking any medication. The drug information contained here in is subject to change and is not intended to cover all possible uses, directions, precautions, warnings, drug interactions, allergic reactions, or adverse effects. The absence of warnings or other information for a given drug does not indicate that the drug or drug combination is safe, effective, or appropriate for all patients or all specific uses.