Key takeaways

  • Furosemide can cause side effects that range from mild to serious. More common side effects include dizziness, headache, nausea, and increased urination.
  • If furosemide side effects become difficult to tolerate, talk with your doctor about coping tips or other treatment options.
  • Older adults may have an increased risk of experiencing side effects from furosemide. This could be due to other health conditions they may have or the increased risk of having reduced kidney function.

Furosemide is a generic prescription drug used to treat:

Furosemide comes as an oral tablet and an oral liquid solution. It also comes in injectable forms, but those are not covered in this article.

This article describes furosemide’s side effects (also called adverse effects). For more information about furosemide, including its uses, see this in-depth article.

Furosemide has a boxed warning. A boxed warning is the most serious warning from the Food and Drug Administration (FDA). For details, see the “Boxed warning for furosemide” section.

Furosemide 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. Talk with your doctor if side effects do not go away, get worse, or become too difficult to tolerate.

Examples of the drug’s more commonly reported side effects include:

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Furosemide can cause mild side effects. Examples that have been reported include:

In most cases, these side effects should be temporary. And some may be easily managed. But if you have symptoms that are ongoing or bother you, talk with your doctor or pharmacist. And do not stop taking furosemide unless your doctor recommends it.

Furosemide may cause mild side effects other than those listed above. See the drug’s prescribing information for details.

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

Serious side effects that have been reported include:

If you develop serious side effects while taking furosemide, 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.

Note: After the Food and Drug Administration (FDA) approves a drug, it tracks and reviews side effects of the medication. Sharing your experience helps make medication safer for everyone by giving doctors and researchers more information about how the drug works in real life. If you develop a side effect while taking furosemide and want to tell the FDA about it, visit MedWatch or call 800-FDA-1088.

Allergic reaction

For some people, furosemide can cause an allergic reaction.

In general, symptoms of an allergic reaction can be mild or serious.

What might help

If you have mild symptoms of an allergic reaction, such as a mild rash, call your doctor right away. They may suggest a treatment to manage your symptoms and can determine whether you should continue furosemide treatment.

If you have symptoms of a severe allergic reaction, such as swelling or difficulty breathing, call 911 or your local emergency number right away. These symptoms could be life threatening and require immediate medical care.

If your doctor confirms you’ve had a serious allergic reaction to furosemide, they may have you switch to a different treatment.

Doctors prescribe furosemide to treat edema in children of all ages. In general, side effects of furosemide in children are similar to those seen in adults who take the drug. Examples are described throughout this article.

Premature infants or children under 4 years of age who take furosemide may have an increased risk of developing kidney stones.

If you have questions or concerns about furosemide’s side effects in children, talk with your child’s doctor.

Furosemide is removed from your body by your kidneys. If your kidneys don’t work well, furosemide can build up in your system. This can increase your risk of side effects. Older adults (ages 65 years and above) are more likely to have reduced kidney function than younger people.

Older people are also more likely to have other health conditions that could increase their risk of side effects with furosemide. And they’re more likely to take other medications that could interact with furosemide and cause side effects.

If you’re age 65 years or older, be sure to tell your doctor about any medical conditions you have and any medications you take before starting furosemide. To be safe, your doctor will likely prescribe a furosemide dosage that’s lower than usual. They may also monitor your kidney function during treatment.

Get answers to some frequently asked questions about furosemide’s side effects.

Does the risk of side effects with furosemide depend on the strength (such as 20-mg vs. 40-mg tablets)?

As with many medications, the risk of side effects with furosemide depends on the dosage you take. You’re more likely to have side effects with a higher dose.

But many other factors can also affect your risk of side effects. These include how well your kidneys work, other medical conditions you have, and other medications you take.

Talk with your doctor if you’re concerned about the risk of side effects with the dosage of furosemide they prescribe.

Does furosemide cause hair loss?

No, it’s not known to. Hair loss hasn’t been reported with furosemide. Certain other blood pressure medications have been reported to cause hair loss in some people. For example, certain beta-blockers and ACE inhibitors can sometimes cause hair loss or thinning.

If you have hair loss that’s bothersome to you, talk with your doctor. They can help you to determine a possible cause.

Are there any long-term side effects of furosemide?

Furosemide can cause some long-term side effects, but these are rare. For example, it might cause tinnitus (ringing in your ears) or hearing problems that could last for a long time or even be permanent. But this is rare.

And certain other rare side effects may last a long time after stopping treatment. Examples include liver problems and problems with your blood cells. But these problems are very unlikely to affect you.

Most of furosemide’s side effects are easily managed or get better quickly as your body gets used to the drug. Others may continue during treatment but get better soon after you stop taking the drug.

If you take furosemide for a long period of time, your doctor will order blood and urine tests to monitor you for side effects.

If you’re concerned about long-term side effects with furosemide, talk with your doctor.

Furosemide has a boxed warning for the risk of dehydration. A boxed warning is the most serious warning from the Food and Drug Administration (FDA). It alerts doctors and patients about drug effects that may be dangerous.

Furosemide works by increasing urination. Taking too much furosemide can cause your body to lose excessive amounts of water and electrolytes (minerals such as potassium and sodium) in your urine. This can lead to dehydration.

Symptoms of dehydration include:

Dehydration can be mild to severe. Severe dehydration needs to be treated in a hospital. If not treated, it can lead to dangerous complications such as kidney failure and shock.

If you have diarrhea or vomiting while taking furosemide, this can increase your risk of dehydration. Sweating more than usual (if you have a fever, for example) can also increase your risk.

What might help

It’s important to drink enough fluids to avoid dehydration while taking furosemide. This is especially important in hot weather or if you’re exercising heavily. This usually means drinking enough to quench your thirst.

You’re likely drinking enough if you’re not thirsty for long periods of time and your urine is pale in color. But how much you should drink will depend on the reason you’ve been prescribed furosemide. Your doctor may recommend limiting how much you drink if you have heart failure or kidney problems. Be sure to talk with them about how much fluid you should drink while taking this drug.

Your doctor will monitor any health conditions you may have while you’re taking furosemide. If needed, they may reduce your dosage of the drug to make sure you’re not at risk of dehydration.

If you become ill with diarrhea, vomiting, or increased sweating while taking furosemide, talk with your doctor right away. They may recommend pausing furosemide until you recover.

If you have symptoms of dehydration, talk with your doctor right away. They’ll advise you on the best course of action, depending on your symptoms and your reason for taking furosemide.

There may be things you can do to help make certain furosemide side effects more manageable. If you have ongoing, worsening, or bothersome side effects, talk with your doctor or pharmacist. They can suggest tips for managing them or recommend other available treatment options for your condition.

Low potassium levels

Furosemide can sometimes cause hypokalemia (low potassium levels in your blood). Potassium is a mineral that helps your muscles, nerves, and organs (especially your heart) work correctly.

Symptoms of hypokalemia can include:

Hypokalemia can be mild to severe. If not treated, severe hypokalemia can lead to dangerous complications such as increased blood pressure, breathing problems, and irregular heart rhythms.

If you have diarrhea or vomiting while taking furosemide, this can increase your risk of hypokalemia. Taking certain other drugs, such as laxatives or corticosteroids, can also increase your risk of this side effect.

What might help

Your doctor will likely order blood tests to monitor your potassium levels while you take furosemide. They may also recommend eating foods high in potassium, such as bananas, avocados, and green leafy vegetables. This can help prevent hypokalemia.

If you have diarrhea, vomiting, or symptoms of hypokalemia while taking furosemide, talk with your doctor right away. If you do have hypokalemia, they may lower your dosage of furosemide. They may also prescribe a potassium supplement to help correct the problem.

Orthostatic hypotension

Furosemide can sometimes cause orthostatic hypotension. This is a temporary drop in your blood pressure that can happen when you get up from a sitting or lying position. It can make you feel dizzy or lightheaded. This can be dangerous because it could make you fall or even faint.

You may have an increased risk of orthostatic hypotension if you’re dehydrated. Taking certain other drugs, especially blood pressure medications, can also increase your risk of this side effect.

What might help

While you’re taking furosemide, move slowly when you’re changing positions. And if you feel dizzy or lightheaded, sit or lie down until the feeling passes.

If you frequently feel dizzy while taking furosemide, talk with your doctor. They may lower your dosage of the drug. Or they may recommend switching to a different treatment for your condition.

Increased urination

Furosemide works by increasing the amount of urine your body produces. So you may need to urinate more often than usual while taking it. Increased urination usually starts about 1 hour after taking a dose and lasts about 6 hours. Depending on when you take furosemide, this could sometimes be inconvenient for you.

What might help

Talk with your doctor about the best time for you to take furosemide. This depends on how often you need to take the drug and how it affects you. In general, it’s best to avoid taking a dose in the late afternoon or evening because it could interrupt your sleep with the need to urinate.

Consider the following important information before starting furosemide.

Furosemide has a boxed warning. A boxed warning is the most serious warning from the FDA. For details, see the “Boxed warnings for furosemide” section.

Other precautions

Before taking furosemide, discuss your health history with your doctor. Furosemide may not be right for you if you have certain medical conditions or other factors affecting your health. Be sure to talk with your doctor if any of the following apply to you:

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 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.