Losartan potassium (Cozaar) is a generic prescription medication used to treat the following conditions:

Losartan comes as an oral tablet. It’s typically a long-term treatment. As with other drugs, losartan can cause side effects (also called adverse effects).

Read on to learn about potential common, mild, and serious side effects of losartan. For a general overview of losartan, including details about its uses, refer to this article. Your doctor can also tell you more about losartan.

Losartan can cause certain side effects, some of which are more common than others. These side effects may be temporary, lasting a few days to weeks. However, if the side effects last longer than that, bother you, or become severe, be sure to talk with your doctor or pharmacist.

These are just a few of the more common side effects reported by people who took losartan in clinical trials. These side effects can vary depending on which condition the drug is being used to treat.

More common side effects of losartan in people with high blood pressure include:

More common side effects of losartan in people with diabetic nephropathy include:

* For more information about this side effect, see “Side effect specifics” below.

Mild side effects can occur with losartan use. These side effects can vary depending on which condition the drug is being used to treat.

This list doesn’t include all possible mild side effects of losartan. For more information, you can refer to the drug’s prescribing information.

Mild side effects that have been reported with losartan when taken for high blood pressure include:

Mild side effects that have been reported with losartan when taken for diabetic nephropathy include:

Mild side effects have not specifically been reported with losartan when taken to lower the risk of stroke.

These side effects may be temporary, lasting a few days to weeks. However, if the side effects last longer than that, bother you, or become severe, be sure to talk with your doctor or pharmacist.

Note: After the Food and Drug Administration (FDA) approves a drug, it tracks side effects of the medication. If you develop a side effect while taking losartan and want to tell the FDA about it, visit MedWatch.

* For more information about this side effect, see “Side effect specifics” below.

Losartan may cause serious side effects. The list below may not include all possible serious side effects of the drug. For more information, you can refer to losartan’s prescribing information.

If you develop serious side effects while taking losartan, call your doctor right away. If the side effects seem life threatening or you think you’re having a medical emergency, immediately call 911 or your local emergency number.

Serious side effects that have been reported and their symptoms include:

  • Low blood pressure. Symptoms can include:
    • fatigue
    • lightheadedness
    • clammy skin
    • blurred vision
  • Anemia (low level of red blood cells). Symptoms can include:
    • pale-looking skin
    • lightheadedness
    • shortness of breath
  • Hyperkalemia (high blood potassium level).*
  • Risk of fetal harm or pregnancy loss.†
  • Severe allergic reaction.‡

* For more information about this side effect, see “Side effect specifics” below.
Losartan has a boxed warning for this side effect. This is the most serious warning from the Food and Drug Administration (FDA). To learn more, see “Pregnancy and breastfeeding while taking losartan” in the “Losartan precautions” section below.
‡ An allergic reaction is possible after taking losartan. This side effect wasn’t reported in clinical trials. However, it has been reported since losartan became available as a prescription. To learn more, see the “Side effect specifics” section below.

The drug manufacturer of losartan doesn’t specify which side effects occurred with the 25-milligram (mg), 50-mg, and 100-mg tablets in clinical trials. In general, the side effects of losartan are expected to be the same regardless of the strength you take.

For details about specific side effects that may occur, see “Losartan: Mild side effects” and “Losartan: Serious side effects” above.

The side effects of losartan may be similar to those of losartan/hydrochlorothiazide (HCTZ), which is available as a brand-name drug called Hyzaar. This is because both medications contain losartan as an active ingredient. So both medications could be expected to cause side effects that happen with losartan.

For details about specific side effects that may occur, see the “Losartan: Mild side effects” and “Losartan: Serious side effects” sections above.

In addition, losartan/HCTZ may cause side effects that occur with HCTZ. (This is a diuretic drug used to treat high blood pressure and other heart conditions.) Examples include weakness and skin sensitivity to the sun. To learn more about the side effects that may occur with HCTZ, see this article.

If you have questions about how the side effects of losartan compare with those of losartan/HCTZ, talk with your doctor.

Losartan may cause several side effects. Here are some frequently asked questions about the drug’s side effects and their answers.

Does losartan cause weight gain or weight loss?

No, losartan isn’t known to cause weight changes. Weight gain and weight loss weren’t reported as side effects in clinical trials of the drug.

However, edema (swelling caused by water retention) is a less common side effect of losartan. And edema may lead to weight gain for some people.

To learn more about weight gain or weight loss and losartan, talk with your doctor. They can advise you on ways to reach or maintain a weight that is healthy for you.

What are the rare side effects of losartan?

Certain side effects of losartan may be less common than others.

A few side effects that were less common in clinical trials of losartan included:

If you have questions about rare side effects of losartan, talk with your doctor or pharmacist.

Does losartan cause leg pain?

It’s possible that Losartan may indirectly cause leg pain, although this side effect wasn’t reported in clinical trials of the drug.

Losartan is known to cause side effects that may lead to leg pain. For example, losartan may cause muscle pain or joint pain.* These side effects can affect the legs, which may be the cause of leg pain.

Losartan may also cause hyperkalemia (high blood potassium level).* Muscle cramps are a symptom of this condition. These cramps may occur in your legs and can be painful.

If you have leg pain with losartan, talk with your doctor. They can tell you whether the leg pain may be caused by losartan or related to another side effect of the drug. Your doctor can also recommend ways to ease leg pain.

* For more information about this side effect, see “Side effect specifics” below.

Learn more about some of the side effects that losartan may cause. To find out how often side effects occurred in clinical trials, see the prescribing information for losartan.

Dry cough

Taking losartan may cause a dry cough for certain people.

Specifically, losartan may cause a dry cough for people who already had a dry cough after taking another class of medications. These drugs are called angiotensin converting enzyme (ACE) inhibitors. ACE inhibitors are used to treat high blood pressure and other heart conditions. These medications commonly cause dry cough as a side effect.

If you had a dry cough while taking an ACE inhibitor, it’s possible you may also have a dry cough with losartan. However, your risk of this side effect is lower with losartan than with an ACE inhibitor.

What you can do

If you’re concerned about a dry cough with losartan, talk with your doctor. They can advise you on your risk of this side effect. Your doctor can also tell you what to do if you have a dry cough with losartan.

Joint pain

Joint pain may occur with losartan. Joint pain was a less common side effect of losartan when the drug was used to treat diabetic nephropathy in clinical trials. This side effect wasn’t reported when losartan was used to treat high blood pressure or lower the risk of stroke. However, joint pain could still occur with any of losartan’s uses.

With joint pain, you may have stiffness, swelling, or tenderness in the affected joint.

What you can do

If you have joint pain with losartan, talk with your doctor. They can recommend ways to ease this side effect. For example, they may recommend an over-the-counter (OTC) pain reliever such as Tylenol (acetaminophen).

However, taking losartan with certain OTC pain relievers can increase the risk of acute (sudden) kidney failure. Specifically, this risk is increased when losartan is taken with nonsteroidal anti-inflammatory drugs (NSAIDs). Examples of NSAIDs include Advil, Motrin (ibuprofen), and Aleve, Naprosyn (naproxen). For this reason, your doctor will likely recommend that you avoid NSAIDs while taking losartan.

Hyperkalemia

Taking losartan may lead to hyperkalemia (high blood potassium level). In clinical trials, this side effect was common in people with diabetic nephropathy. Hyperkalemia wasn’t reported when losartan was used to treat high blood pressure or lower the risk of stroke. However, hyperkalemia is still possible with any of losartan’s uses.

Hyperkalemia may not cause any symptoms unless it’s severe. Possible symptoms can include:

The risk of hyperkalemia with losartan is increased when the drug is taken with other medications that cause high potassium. Examples include potassium-sparing diuretics such as Aldactone (spironolactone) and Inspra (eplerenone).

What you can do

Before taking losartan, tell your doctor about all other medications you take. They can tell you if any of these medications may increase your risk of hyperkalemia. If you take these treatments with losartan, your doctor may check your blood potassium level frequently.

If you have symptoms of hyperkalemia with losartan, tell your doctor right away. They’ll recommend whether you need treatment to lower your potassium level.

Allergic reaction

As with most drugs, losartan can cause an allergic reaction in some people. This side effect wasn’t reported in clinical trials. However, there have been rare reports of allergic reactions to losartan since the drug became available through prescription.

Symptoms can be mild or serious and can include:

  • skin rash
  • itching
  • flushing
  • swelling under your skin, typically in your eyelids, lips, hands, or feet
  • swelling of your mouth, tongue, or throat, which can make it hard to breathe

What you can do

For mild symptoms of an allergic reaction, call your doctor right away. They may recommend ways to ease your symptoms and determine whether you should keep taking losartan. However, if your symptoms are serious and you think you’re having a medical emergency, immediately call 911 or your local emergency number.

Keep reading to learn more about losartan warnings, which may affect whether you can safely take the medication.

Boxed warning: Fetal harm or pregnancy loss

This drug has a boxed warning for the risk of fetal harm or pregnancy loss. This is a serious warning from the Food and Drug Administration (FDA). For details, see “Pregnancy and breastfeeding while taking losartan” below.

Other precautions

Be sure to talk with your doctor about your health history before you take losartan. This drug may not be the right treatment option for you if you have certain medical conditions or other factors that affect your health. These are known as drug-condition or drug-factor interactions. The conditions and factors to consider include:

Liver problems. Before starting losartan, tell your doctor if you have liver problems. An example is liver failure. If you have liver problems, your body may not break down losartan as well as it should. This could lead to a high level of losartan in your body, which could increase your risk of side effects. To reduce your risk of side effects, your doctor may give you a lower dosage of losartan than is typical. To learn more about losartan’s dosage, see this article.

Kidney problems. Losartan may cause acute (sudden) kidney failure in people who already have kidney problems. Examples include chronic kidney disease and renal artery stenosis. If you have kidney problems, be sure to tell your doctor before taking losartan. They’ll recommend whether it’s safe for you to take losartan. In some cases, they may prescribe a different treatment option for you instead.

Allergic reaction. If you’ve had an allergic reaction to losartan or any of its ingredients, your doctor will likely not prescribe losartan. Taking losartan could cause you to have another allergic reaction. Ask your doctor what other medications may be better options for you.

Taking aliskiren with diabetes. Before taking losartan, tell your doctor if you take a blood pressure drug called Tekturna (aliskiren) and have diabetes. Taking these medications together can increase your risk of certain side effects of losartan. These include hyperkalemia (high blood potassium level), low blood pressure, and acute (sudden) kidney failure. Your doctor will likely prescribe a drug other than losartan for you.

Alcohol with losartan

There is no known interaction between alcohol and losartan.

However, alcohol and losartan may cause some of the same side effects. Your risk of these side effects could be increased if you consume alcohol while taking losartan.

Examples of the side effects that both alcohol and losartan may cause can include:

If you drink alcohol, talk with your doctor before starting losartan treatment. They can tell you whether there’s an amount that’s safe to drink while taking the drug.

* Losartan has a boxed warning for this side effect. This is the most serious warning from the Food and Drug Administration (FDA). To learn more, see “Pregnancy and breastfeeding while taking losartan” below.

Pregnancy and breastfeeding while taking losartan

Below is important information about taking losartan while pregnant or breastfeeding.

Pregnancy

Losartan is not safe to take during pregnancy. The drug has a boxed warning for the risk of fetal harm or pregnancy loss. This is a serious warning from the FDA. It alerts doctors and patients about drug effects that may be dangerous.

If taken during pregnancy, losartan may cause harm to a fetus. Below are examples of problems that may occur in a fetus:

In some cases, these problems may lead to long-term side effects in the infant after birth. These problems could also be fatal for the fetus and lead to pregnancy loss.

The risk of fetal harm with losartan is highest during the second and third trimesters of pregnancy. If you become pregnant during losartan treatment, stop taking the drug. Tell your doctor about the pregnancy right away.

If you’re planning to become pregnant, talk with your doctor before starting losartan treatment. They’ll likely advise you to use an effective form of birth control while taking the drug.

Breastfeeding

It isn’t known whether losartan is safe to take while breastfeeding. Animal trials have shown that the drug can pass into breast milk. However, animal trials don’t always predict what will happen in humans.

If you’re breastfeeding or planning to breastfeed, talk with your doctor before taking losartan. They can discuss the risks and benefits of taking losartan if you are considering breastfeeding.

Both mild and serious side effects may occur with losartan. However, most of the drug’s side effects are expected to be mild and should go away with time. If you have side effects that are bothersome during losartan treatment, talk with your doctor.

If you’d like to learn more about losartan, talk with your doctor or pharmacist. They can help answer any questions you have about side effects of taking the drug. You can also ask them about Cozaar, the brand-name version of losartan.

A generic drug and its brand-name version contain the same active ingredient, so they’re expected to have the same side effects. Referring to the following articles about losartan can provide you with additional information:

Disclaimer: Medical News Today 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 another 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.