What to Know About Cozaar (Losartan)

A Medication for Treating High Blood Pressure

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Cozaar (losartan potassium, also known as losartan), is a commonly used oral medication for treating high blood pressure (hypertension) and complications of other diseases affected by high blood pressure. It is not a cure for the condition, simply a way to manage it.

Researchers are also looking into its possible uses to treat complications of COVID-19, although its effectiveness is not yet known. Cozaar (losartan) belongs to a class of medications known as angiotensin II receptor blockers (ARBs). It is taken in tablet form.

As an angiotensin II receptor blocker, losartan helps your blood vessels to relax in order to lower your blood pressure and make it easier for your heart to pump blood through your body. It does this by blocking the action of the hormone angiotensin II, which otherwise works to narrow your veins and arteries, increase blood pressure, and cause your body to retain more fluid and sodium.

Nurse checking blood pressure for person taking losartan for high blood pressure
 vitapix / E+ / Getty Images


Losartan is FDA-approved to lower blood pressure that is too high, meaning that you have a systolic pressure in your arteries (when your heart is beating) of 130 mm Hg or higher or a diastolic pressure (between heartbeats) of 80 mm Hg or higher.

The drug is also FDA-approved to lower the risk of stroke in people who have high blood pressure and left ventricular hypertrophy, a heart condition also known as an having an enlarged heart. However, it may not lower the risk of stroke in Black people who have those conditions.

Further, losartan is FDA-approved to treat kidney damage in people who have type 2 diabetes, a condition that occurs when the body does not use insulin effectively and blood glucose (sugar) rises too high.

Off-Label Uses

Patients with serious COVID-19-related lung damage have been observed to have higher than normal levels of angiotensin II in their bodies. That hormone constricts your blood vessels, increases blood pressure, and causes your body to retain more fluid. Losartan helps to block those actions by angiotensin II in people with hypertension.

This is among the reasons why researchers looking into losartan for treating COVID-19 patients, though there isn’t enough data yet to confirm its effectiveness. Among them is a clinical trial for hospitalized patients that is scheduled to conclude in April 2021.

Before Taking

If you have the following conditions, you may be prescribed losartan alone or in combination with other medications:

  • High blood pressure
  • Type 2 diabetes and kidney damage
  • High blood pressure and enlargement of the heart

Talk to your healthcare provider about all medications, supplements, and vitamins that you currently take. While some drugs pose minor interaction risks, others may outright contraindicate use or prompt careful consideration as to whether the pros of treatment outweigh the cons in your case.

Precautions and Contraindications

People who are pregnant or planning to become pregnant should not take this medication, as it may cause death or serious injury to a fetus during the last six months of pregnancy. This also applies when losartan is also taken in combination with the diuretic hydrochlorothiazide, under the brand name Hyzaar.

You should tell your healthcare provider if you have ever had kidney or liver disease, heart failure, as this information will guide your practitioner on how and whether to prescribe it. Also, disclose if you are allergic to losartan or you have diabetes and also take aliskiren (under the brand name Tekturna, and in Amturnide, Tekamlo, Tekturna HCT). You will likely be directed not to take losartan under those circumstances.

Tell your healthcare provider if you are breastfeeding, as small amounts of the drug may end up in your breast milk and could lower the blood pressure of your infant.

Not everyone reacts to ARBs such as losartan in the same manner. A 2018 review of hypertension studies noted that Black patients are, on average, less responsive to ARB medications (when used alone) than White patients.

However, ARB treatment was found to be just as effective in Black people when used in combination with one or both of the following blood pressure-lowering medications: thiazide diuretics, which cause you to shed body fluid by increasing urine flow; and calcium channel blockers, which relax narrowed blood vessels.

There also is evidence that losartan may not lower the risk of stroke in Black people who have both hypertension and enlarged hearts.

Other Angiotensin Receptor Blockers

Other angiotensin receptor blockers (ARBs) have similar contraindications. They include:

  • Atacand (candesartan)
  • Avapro (irbesartan)
  • Benicar (olmesartan)
  • Diovan (valsartan)
  • Edarbi (azilsartan)
  • Micardis (telmisartan)
  • Teveten (eprosartan)


Losartan is typically taken by mouth in the following dosages, according to the condition being treated.


  • Adults: 50 milligrams (mg) a day
  • Children: Starting at 0.7 mg per kilogram of weight per day, up to 50 mg.

Hypertensive patients with enlarged heart have a usual starting dose of 50 mg a day. Type 2 diabetes patients with kidney disease have a usual dose of 50 mg a day

All listed dosages are according to the drug manufacturer. Check your prescription and talk to your healthcare provider to make sure you are taking the right dose for you.

How to Take and Store

Losartan should be taken exactly as prescribed by your healthcare provider. It can be taken with or without food. If you miss a dose, take it as soon as you remember; but, if it is close to your next dose, don’t take the missed dose. Just take the next dose at the regular time.

If you take too much losartan, call your healthcare provider or a poison control center or seek emergency medical attention.

Keep losartan in a tightly closed container that protects the medication from light. It should be stored at a temperature between 59 F and 86 F (between 15 C and 30 C). Keep it out of the reach of children.

Side Effects


The more common side effects of taking Losartan include the following:

  • Dizziness or vertigo
  • Headache
  • Nausea
  • Vomiting
  • Diarrhea
  • Joint pain
  • Muscle aches


Rare, but serious side effects may include:

  • Jaundice: Skin turns yellowish.
  • Inflamed pancreas: Severe stomach pain is a symptom.
  • Blood or bone marrow disorders: Fatigue, fever, paleness or purple spots may be signs.
  • Changes in the sodium and potassium levels in your blood: Can cause muscle cramps or irregular heartbeat.
  • A serious allergic reaction: Wheezing, difficulty breathing, rashy skin, swollen tongue or throat are signs of anaphylaxis, a potentially life-threatening condition.
  • Low blood pressure
  • Damage to fetus

See your healthcare provider about any side effects and if you are having an allergic reaction, seek emergency medical attention.

Warnings and Interactions

Black Box Warning

The FDA has a black box warning (the strongest warning the agency issues on its labels) against for losartan for fetal toxicity. Discontinue this medication (also known as Cozaar), or any medication containing losartan, such as Hyzaar, as soon as a pregnancy is detected.

Possible Drug Interactions

As well, the following medications may interfere with the way losartan works, so let your healthcare provider know if you also take:

  • Other blood pressure drugs, including aliskiren, enalapril, captopril, lisinopril or ramipril
  • Non-steroidal anti-inflammatory drugs (NSAID) pain relievers, such as ibuprofen, naproxen, diclofenac, celecoxib, or etoricoxib
  • More than 3 grams of aspirin a day
  • Potassium supplements or salt substitutes containing potassium
  • Spironolactone and other diuretics (water pills)
  • The blood thinner heparin
  • The psychiatric medication lithium


Losartan was among a number of drugs subject to FDA recalls between 2018 and 2020 because they were found to contain unacceptably high levels of a nitrosamine, a potentially cancer-causing substance. The impurities are thought to have been introduced during the manufacturing process.

The FDA has an ARB Recalls List database you can check to see if any bottle of losartan in your medicine cabinet is among the recalled lots.

In the meantime, the FDA recommends that you do not stop taking your medicine, even if it is among the recalled lots. Instead, let your pharmacist know so they can provide a replacement or a different treatment option. Not all bottles of losartan have the impurity, so you can find an option that does not contain the impurity.

10 Sources
Verywell Health uses only high-quality sources, including peer-reviewed studies, to support the facts within our articles. Read our editorial process to learn more about how we fact-check and keep our content accurate, reliable, and trustworthy.
  1. Society for Endocrinology. Angiotensin.

  2. American Heart Association. What is high blood pressure?

  3. MedlinePlus. Losartan.

  4. Yeager A. Blood pressure meds point the way to possible COVID-19 treatment. TheScientist.

  5. University of Minnesota. Losartan for patients with COVID-19 requiring hospitalization. U.S. National Library of Medicine. ClinicalTrials.gov Identifier: NCT04312009.

  6. DailyMed. HYZAAR- losartan potassium and hydrochlorothiazide tablet, film coated. [Package insert.] Merck Sharp & Dohme Corp.

  7. U.S. Food and Drug Administration. COZAAR (losartan potassium) tablets, for oral use. [Package Insert]. Merck & Co., Inc.

  8. Helmer A, Slater N, Smithgall S. A review of ACE inhibitors and ARBs in Black patients with hypertension. Ann Pharmacother. 2018;52(11):1143-1151. doi:10.1177/1060028018779082

  9. U.S. Food and Drug Administration. Angiotensin receptor blockers (ARBs) information.

  10. U.S. Food and Drug Administration. Recalls of angiotensin II receptor blockers (ARBs) including valsartan, losartan and irbesartan.

By Sheryl Huggins Salomon
Sheryl Huggins Salomon is a veteran editor and health journalist specializing in coverage of metabolic health, skin conditions, and BIPOC health trends.