If you have high blood pressure or edema (fluid buildup), you may be interested in learning more about furosemide. It’s a generic prescription drug used to treat:

Your doctor may recommend taking furosemide on a long-term or short-term basis. This depends on your reason for taking furosemide and how your body responds to the drug.

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.

Some people may experience mild to serious side effects during their furosemide treatment. Examples of the drug’s more commonly reported side effects include:

* To learn more about this side effect, see the “Side effects explained” section below.

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

* To learn more about this side effect, see the “Side effects explained” section below.

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.

Note: After the Food and Drug Administration (FDA) approves a drug, it tracks side effects of the medication. If you’d like to notify the FDA about a side effect you’ve had with furosemide, visit MedWatch.

Serious side effects have been reported with furosemide. These 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.

* To learn more about this side effect, see the “Side effects explained” section below.

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.

Possibly. 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.

Learn more about some of the side effects furosemide may cause.

Risk of dehydration

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.

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.

Allergic reaction

Like most drugs, furosemide can cause an allergic reaction in some people.

Symptoms can be mild to serious and can include:

  • skin rash
  • itchiness
  • flushing (temporary warmth, redness, or deepening of skin color)
  • swelling under your skin, usually in your eyelids, lips, hands, or feet
  • swelling of your mouth, tongue, or throat, which can make it hard to breathe

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. Examples include:

  • an antihistamine you take by mouth, such as Benadryl (diphenhydramine)
  • a product you apply to your skin, such as hydrocortisone cream

If your doctor confirms you’ve had a mild allergic reaction to furosemide, they’ll decide whether you should continue using it.

If you have symptoms of a severe allergic reaction, such as swelling or trouble 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.

Keeping track of side effects

During your furosemide treatment, consider taking notes on any side effects you’re having. You can then share this information with your doctor. This is especially helpful when you first start taking new drugs or using a combination of treatments.

Your side effect notes can include things such as:

  • what dose of the drug you were taking when you had the side effect
  • how soon you had the side effect after starting that dose
  • what your symptoms were
  • how it affected your daily activities
  • what other medications you were taking
  • any other information you feel is important

Keeping notes and sharing them with your doctor will help them learn more about how furosemide affects you. They can then use this information to adjust your treatment plan if needed.

Furosemide comes with several warnings, including a boxed warning.

Boxed warning: Risk of dehydration

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).

To learn more, see the “Side effects explained” section above.

Other warnings

Furosemide may not be right for you if you have certain medical conditions. This is known as a drug-condition interaction. Other factors may also affect whether furosemide is a good treatment option for you. Talk with your doctor about your health history before starting furosemide. Factors to consider include those described below.

Allergic reaction. If you’ve had an allergic reaction to furosemide or any of its ingredients, your doctor will likely not prescribe it for you. If you’ve had a past allergic reaction to a sulfonamide (sulfa) drug, you may also be allergic to furosemide. Talk with your doctor about other medications that might be better options for you.

Kidney problems. Furosemide is removed from your body by your kidneys. If you have kidney problems, furosemide could build up in your body, which could increase your risk of side effects. Your doctor will likely prescribe a furosemide dosage that’s lower than usual if you have kidney problems. And they’ll likely monitor your kidney function during treatment to make sure the medication remains safe for you.

Urinary retention. Furosemide increases the amount of urine your kidneys produce. If you have urinary retention (trouble fully emptying your bladder), taking furosemide could cause urine to build up in your bladder. This could be dangerous. If you have urinary retention or trouble urinating (due to an enlarged prostate, for example), talk with your doctor about whether furosemide is right for you. If you’re not urinating at all, your doctor will likely not prescribe this drug. Ask them what other medications might be better options for you.

Electrolyte imbalance. Furosemide can cause electrolyte imbalances, such as low levels of sodium, potassium, magnesium, or calcium in your blood. If you already have an electrolyte imbalance, furosemide could make it worse. Your doctor will likely prescribe medication to correct any electrolyte imbalances before you start taking furosemide.

Diabetes. Furosemide can increase your blood sugar levels, which could make diabetes harder to manage. If you have diabetes, talk with your doctor about whether furosemide is right for you. They may want to monitor your blood sugar more often while you’re taking this drug.

Gout. Furosemide can increase the level of uric acid in your blood, which could worsen gout. If you have gout, talk with your doctor about whether this drug is right for you.

Liver problems. If you have liver problems such as cirrhosis or ascites, you may have an increased risk of electrolyte imbalance with furosemide. Electrolyte imbalance could increase your risk of liver damage. Due to this risk, you’ll likely start treatment with furosemide in the hospital. Your doctor will monitor your fluid and electrolyte balance during treatment to make sure the drug remains safe for you.

Thyroid problems. If you have a thyroid problem, taking high doses of furosemide could make your condition worse. Talk with your doctor about whether furosemide is right for you.

Alcohol and furosemide

Drinking alcohol with furosemide may increase your risk of certain side effects. These include:

If you drink alcohol, talk with your doctor about whether it’s safe to do so while you’re taking furosemide. They may recommend limiting your alcohol intake or avoiding it altogether while you’re taking this drug.

Pregnancy and breastfeeding while taking furosemide

It’s not known if furosemide is safe to take during pregnancy. If you’re pregnant or planning to become pregnant, talk with your doctor about the possible risks and benefits of taking this drug.

Furosemide can pass into breast milk and may cause side effects in a child who is breastfed. If you’re breastfeeding or planning to breastfeed, talk with your doctor about other healthy ways to feed your child while taking this drug.

Most of furosemide’s side effects are mild and easily managed. But, like many medications, furosemide can cause serious side effects in rare cases. If you have questions about side effects this drug can cause, talk with your doctor.

You can also ask them about Lasix, which is the brand-name version of furosemide. A generic drug and its brand-name version are expected to have the same side effects because they contain the same active ingredient. (An active ingredient is what makes a drug work.)

Examples of some questions you might want to ask your doctor include:

  • Do I have a high risk of side effects with furosemide due to medical conditions I have or other drugs I take?
  • Does the dose of furosemide I need come with a high risk of side effects?
  • How do furosemide’s side effects compare with other treatment options for my condition?
  • What monitoring will I need while taking this drug?

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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 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.