Key takeaways

  • Nitrofurantoin, an antibiotic for urinary tract infections, may cause common side effects like vomiting, gas, diarrhea, and headaches. These side effects are usually temporary.
  • Serious side effects from nitrofurantoin are rare but may include pancreatitis, nerve damage, liver problems, and severe allergic reactions. These serious side effects require immediate medical attention.
  • Taking nitrofurantoin may change the color of your urine and affect urine sugar test results. Individuals with preexisting conditions like kidney or liver problems should consult their doctor before use.

Nitrofurantoin, which is used to treat urinary tract infections (UTIs) in adults and some children, can cause side effects. This article will cover its more common, mild, and serious side effects and how to manage them.

Nitrofurantoin is a generic prescription antibiotic that comes as an oral capsule that you swallow. One kind of capsule contains two forms of the drug, nitrofurantoin monohydrate/macrocrystals. Another kind contains only nitrofurantoin macrocrystals. The drug also comes as an oral suspension, which is a kind of liquid mixture that you swallow.

This article covers nitrofurantoin monohydrate/macrocrystals capsules only. The brand-name version of this generic capsule is Macrobid. To learn more about other forms of nitrofurantoin, talk with your doctor or pharmacist.

Because nitrofurantoin is used to treat an infection, you’ll take the drug only for a short time.

This article describes nitrofurantoin’s side effects. For more information about nitrofurantoin, including its uses, dosage, and cost, see this nitrofurantoin overview article.

Some people may experience mild to serious side effects during their nitrofurantoin treatment. Examples of nitrofurantoin’s most commonly reported side effects include:

  • vomiting
  • gas
  • diarrhea
  • headache
  • constipation

For more information about some of these side effects, see “Tips for managing side effects.”

It’s possible to have mild side effects from taking nitrofurantoin. Examples of mild side effects that have been reported with nitrofurantoin include:

For more information about some of these side effects, see “Tips for managing side effects.”

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

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

Serious side effects from nitrofurantoin are possible but not common. Serious side effects that have been reported with nitrofurantoin include:

If you develop serious side effects while taking nitrofurantoin, 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 nitrofurantoin and want to tell the FDA about it, visit MedWatch or call 800-FDA-1088.

Allergic reaction

For some people, nitrofurantoin 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 keep taking nitrofurantoin.

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 nitrofurantoin, they may have you switch to a different treatment.

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

Body aches and joint pain

Nitrofurantoin can cause body aches and joint pain. But it’s not clear how often these side effects occurred in studies of the drug.

What might help

If you develop body aches or joint pain during your treatment with nitrofurantoin, tell your doctor. They may be able to recommend ways to ease any discomfort that you have. For example, they may suggest taking an over-the-counter (OTC) pain reliever such as Tylenol (acetaminophen) or Advil (ibuprofen).

Body aches may be a symptom of a fever, which can occur from a urinary tract infection (UTI), the condition nitrofurantoin is used to treat. If you have body aches, your doctor can check to make sure that the drug is working to treat your UTI.

Nausea

You may have nausea from taking nitrofurantoin. Nausea was one of the most common side effects that people taking nitrofurantoin reported in studies.

What might help

It’s recommended that you take nitrofurantoin with food. In addition to helping the drug work more effectively, it may also help prevent nausea.

If you notice nausea from taking nitrofurantoin, tell your doctor. They can recommend ways to help prevent or treat your nausea.

Learn more about how to get rid of nausea.

Headache

Nitrofurantoin can cause headache. In studies, this was one of the most commonly reported side effects of the drug.

What might help

If you have headaches from taking nitrofurantoin, tell your doctor. They can help recommend ways to treat this side effect. For example, they may suggest taking an OTC medication, such as Tylenol (acetaminophen), to lessen your headaches.

Stomach (belly) pain

It’s possible to have stomach (belly) pain from taking nitrofurantoin. But studies of the drug didn’t report how often this side effect occurred.

What might help

If you have belly pain during nitrofurantoin treatment, let your doctor know. In rare cases, this may be a symptom of a more serious side effect. Examples include pancreatitis and liver problems.

Your doctor will check to see what may be causing your belly pain. In addition, they can recommend ways to ease this pain.

Constipation

Nitrofurantoin can cause constipation, although studies did not report how often this side effect occurred.

Symptoms of constipation include straining when having a bowel movement or going to the bathroom less often than usual.

What might help

If you have constipation from taking nitrofurantoin, tell your doctor. They can recommend ways to decrease your constipation. For example, they may suggest increasing your fiber or taking an OTC medication such as MiraLAX (polyethylene glycol).

Learn more about tips and remedies for constipation relief.

Keeping track of side effects

During your nitrofurantoin 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 symptoms may have 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 nitrofurantoin affects you. They can then use this information to adjust your treatment plan if needed.

Here are answers to some frequently asked questions (FAQ) about nitrofurantoin’s side effects.

Will taking nitrofurantoin monohydrate/macrocrystals 100 mg increase my risk of side effects compared with taking nitrofurantoin macrocrystals 100 mg?

It’s probably unlikely. You should experience similar side effects from both nitrofurantoin monohydrate/macrocrystal capsules (Macrobid) and nitrofurantoin macrocrystals capsules (Macrodantin). This is because both drugs contain similar ingredients.

Nitrofurantoin capsules can contain one form of the drug, nitrofurantoin macrocrystals, or two forms of the drug, nitrofurantoin monohydrate/macrocrystals.

Both versions of nitrofurantoin come in a strength of 100 milligrams (mg). (Nitrofurantoin monohydrate/macrocrystals capsules contain 75 mg of nitrofurantoin monohydrate and 25 mg of nitrofurantoin macrocrystals.) Nitrofurantoin macrocrystals is also available in other strengths.

Both kinds of nitrofurantoin capsule are used to treat urinary tract infections (UTIs). But nitrofurantoin macrocrystals can also be used to help prevent UTIs.

Nausea may occur more often in people taking nitrofurantoin monohydrate/macrocrystals than in people taking nitrofurantoin macrocrystals. If you have nausea from taking the former, talk with your doctor about switching to nitrofurantoin macrocrystals.

This article covers side effects of only nitrofurantoin monohydrate/macrocrystals capsules. If you have questions or concerns about the side effects of nitrofurantoin macrocrystals capsules, talk with your doctor.

How long do nitrofurantoin side effects last?

In most cases, mild side effects of nitrofurantoin should be temporary and can be easily managed. But if you have any symptoms of mild side effects that are long lasting or bother you, talk with your doctor or pharmacist.

Serious side effects of nitrofurantoin can be dangerous and can have long-lasting health effects. Call your doctor right away if you have symptoms of these side effects. If you think you’re having a medical emergency related to nitrofurantoin side effects, immediately call 911 or your local emergency number.

Do older adults have a higher risk of side effects from nitrofurantoin?

It’s not known whether adults ages 65 years and older have a higher risk of side effects from nitrofurantoin. Studies of the drug did not include enough older adults to determine whether they may have a higher risk of side effects.

But older adults may have a higher risk of kidney problems than younger people. Since the kidneys work to break down nitrofurantoin, having kidney problems may cause the drug to build up in the body. This can increase the risk of side effects from nitrofurantoin.

If you’re an older adult and have concerns about your risk of nitrofurantoin’s side effects, talk with your doctor or pharmacist.

Could taking nitrofurantoin affect my urine?

Yes, it’s possible. For example, nitrofurantoin may cause your urine to turn brown. After you stop taking the medication, your urine will go back to its usual color.

Taking nitrofurantoin may also cause a false-positive urine sugar test. This is a test that can check for diabetes. If you need to have a urine sugar test during treatment with nitrofurantoin, tell your doctor that you’re taking this drug. They may be able to recommend a different test to check your sugar level.

Nitrofurantoin may not be right for you if you have certain medical conditions. These are known as drug-condition interactions. Other factors may also affect whether nitrofurantoin is a good treatment option for you.

Talk with your doctor about your health history before starting nitrofurantoin. Factors to consider include those described below.

Peripheral neuropathy. Nitrofurantoin can cause peripheral neuropathy. If you already have this kind of nerve damage, taking nitrofurantoin may make your condition worse. Before taking nitrofurantoin, tell your doctor if you have nerve damage. This will help them determine whether the drug is safe for you to take.

Liver conditions. Nitrofurantoin can cause liver problems, including liver damage. If you have a liver condition, taking this drug may worsen your condition. Let your doctor know about any liver problems you have before starting nitrofurantoin treatment. They’ll discuss with you whether it’s safe for you to take the drug.

Glucose-6-phosphate dehydrogenase deficiency (G6PD deficiency). If you have G6PD deficiency, tell your doctor before starting nitrofurantoin treatment. This genetic condition may increase your risk of hemolytic anemia if you take nitrofurantoin. Your doctor may monitor you more closely for this side effect during treatment. Or they may recommend a medication other than nitrofurantoin for your condition.

Allergic reaction. If you’ve had an allergic reaction to nitrofurantoin or any of its ingredients, your doctor will likely not prescribe nitrofurantoin. Ask them what other medications are better options for you.

Lung conditions. Although rare, it’s possible for nitrofurantoin to cause lung problems. If you already have a lung condition, the drug may increase your risk of this side effect. Tell your doctor about any lung conditions that you have before taking nitrofurantoin. This will help them determine whether nitrofurantoin may be safe for you to take.

Kidney problems. It may not be safe for people with certain kidney conditions to take this drug. If you have any kidney problems, tell your doctor before taking nitrofurantoin. They can determine whether nitrofurantoin is a good treatment option for you. Depending on how severe your kidney problem is, your doctor may recommend a different treatment for your condition.

Alcohol and nitrofurantoin

It might be safe to drink alcohol during your nitrofurantoin treatment. But drinking alcohol during your treatment with this medication may increase your risk of certain side effects. Examples include:

For more information about some of these side effects, see “Tips for managing side effects.”

If you’d like to drink alcohol while taking nitrofurantoin, talk with your doctor. They can let you know how much alcohol, if any, may be safe for you to consume during treatment.

Pregnancy and breastfeeding while taking nitrofurantoin

It’s not known whether it’s safe to take nitrofurantoin while pregnant. At this time, there aren’t enough studies to determine what risks nitrofurantoin may cause in someone taking the drug during pregnancy.

But it’s important to note that anyone who is pregnant should not take nitrofurantoin after week 37 of pregnancy. This drug can cause hemolytic anemia, a condition resulting from red blood cells being destroyed faster than they’re made. Due to this side effect, it’s thought that the drug may cause damage to red blood cells in a newborn.

As a result, doctors will usually prescribe nitrofurantoin during pregnancy only if no safer treatment options are available.

In addition, nitrofurantoin can pass into breast milk. Because of the risk of side effects in a child who is breastfed, doctors usually will not recommend breastfeeding while taking nitrofurantoin.

If you’re pregnant or breastfeeding, or planning to become pregnant or breastfeed, tell your doctor. They can answer any questions you may have about using nitrofurantoin during pregnancy or while breastfeeding.

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.