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 a heart condition called left ventricular hypertrophy.

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.

What’s losartan used for?

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 drug class

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.

How losartan works

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 action helps treat high blood pressure as well as the other two conditions losartan is usually prescribed for. High blood pressure and left ventricular hypertrophy (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 can cause mild or serious side effects. The following list contains some of the key side effects that may occur while taking losartan. This list does not include all possible side effects.

For more information on the possible side effects of losartan, or tips on how to deal with a troubling side effect, talk with your doctor or pharmacist.

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

These effects 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
Edema (or swelling) of the hand

Losartan can interact with several other medications. Different interactions can cause different effects. For instance, some can interfere with how well a drug works, while others can cause increased side effects.

Below is a list of medications that can interact with losartan. This list does not contain all drugs that may interact with losartan.

Before taking losartan, be sure to tell your doctor and pharmacist about all prescription, over-the-counter, and other drugs you take. Also tell them about any vitamins, herbs, and supplements you use. Sharing this information can help you avoid potential interactions.

If you have questions about drug interactions that may affect you, ask your doctor or pharmacist.

Lithium

Taking losartan with lithium, a drug used to treat bipolar disorder, may increase the levels of lithium in your body. This can increase your risk of dangerous side effects.

If you need to take these drugs together, your doctor may reduce your lithium dosage.

Blood pressure drugs

Taking losartan with other drugs that work in the same way may increase your chance of low blood pressure, high potassium levels in your blood, and kidney damage.

Examples of these drugs include:

  • angiotensin receptor blockers (ARBs), such as:
    • irbesartan
    • candesartan
    • valsartan
  • angiotensin-converting enzyme (ACE) inhibitors, such as:
    • lisinopril
    • fosinopril
    • enalapril
    • aliskiren

Nonsteroidal anti-inflammatory drugs (NSAIDs)

You shouldn’t take NSAIDs with losartan. 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
  • 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

Rifampin

Taking losartan with rifampin, a drug used to treat tuberculosis, 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 or supplements that contain potassium

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

Examples of drugs that contain potassium include:

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

The losartan dosage your doctor prescribes will depend on several factors. These include:

  • the type and severity of the condition you’re using losartan to treat
  • your age
  • your weight
  • other medical conditions you may have, such as liver damage

Typically, your doctor will start you on a low dosage and adjust it over time to reach the dosage that’s right for you. They’ll ultimately prescribe the smallest dosage that provides the desired effect.

The following information describes dosages that are commonly used or recommended. However, be sure to take the dosage your doctor prescribes for you. Your doctor will determine the best dosage to suit your needs.

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. As a result, a normal adult dosage may cause levels of this drug to be higher than normal in your body. If you’re a senior, you may need a lower dosage, or a different dosing schedule.

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 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. As a result, a normal adult dosage may cause levels of this drug to be higher than normal in your body. If you’re a senior, you may need a lower dosage, or a different dosing schedule.

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. You may take losartan once or twice per day.

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. As a result, a normal adult dosage may cause levels of this drug to be higher than normal in your body. If you’re a senior, you may need a lower dosage, or a different dosing schedule.

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.

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.

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

Consuming alcoholic drinks while taking losartan can cause a sedative effect. This means you may have slowed reflexes, poor judgment, and sleepiness. This effect can be dangerous if you drive or use other machinery.

Alcohol can also increase the blood pressure-lowering effect of losartan. This increases the risk of your blood pressure getting too low.

Low blood pressure warning

This drug may cause low blood pressure, which can make you 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 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. As a result, a normal adult dosage may cause levels of this drug to be higher than normal in your body. If you’re a senior, you may need a lower dosage, or a different dosing schedule.

For children: This medication should not be used in children younger than 6 years with high blood pressure.

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. High blood pressure increases 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 symptoms such as:

  • feeling like your heart is pounding
  • weakness
  • dizziness

If you think you’ve taken too much of this drug, call your doctor or seek guidance from the American Association of Poison Control Centers at 1-800-222-1222 or through their online tool. But 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°F and 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.

Shop for blood pressure monitors.

Clinical monitoring

During treatment with losartan, your doctor may check your:

  • 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.

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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 herein 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.