If you have a urinary tract infection (UTI), you may be interested in learning more about nitrofurantoin. It’s a generic prescription antibiotic used to treat UTIs in adults and some children.

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

This article covers nitrofurantoin monohydrate/macrocrystal 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 details about its uses, see this in-depth article.

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

  • vomiting
  • gas
  • diarrhea
  • headache*
  • constipation*

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

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

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

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:

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

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. If you’d like to notify the FDA about a side effect you’ve had with nitrofurantoin, visit MedWatch.

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

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

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

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

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

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

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

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

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.

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

Body aches and joint pain

Nitrofurantoin can cause body aches and joint pain. Studies of the drug didn’t report how often these side effects occurred.

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

If you notice nausea from taking nitrofurantoin, tell your doctor. They can recommend ways to help prevent or treat your nausea. You might also try the home remedies discussed in this article.

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

Nausea may occur more often with nitrofurantoin monohydrate/macrocrystal capsules than with nitrofurantoin macrocrystal capsules.* If you’re experiencing nausea from nitrofurantoin monohydrate/macrocrystal, your doctor may recommend switching to nitrofurantoin macrocrystal.

* For more information about these two kinds of nitrofurantoin capsules, see the “FAQs about nitrofurantoin’s side effects” section above.

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.

Check out this article for a few tips that may also help relieve headache pain.

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, which is inflammation (swelling and damage) of the pancreas, 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).

You can also try some of the constipation remedies discussed in this article.

Allergic reaction

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

Symptoms can be mild to serious and may 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 nitrofurantoin, they’ll decide if you should continue taking 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 nitrofurantoin, they may have you switch to a different treatment.

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.

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:

* To learn more about this side effect, see the “Nitrofurantoin’s side effects explained” section above.

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.

In most cases, side effects from nitrofurantoin are mild. But serious side effects are also possible from taking this medication.

If you have any questions about side effects that nitrofurantoin can cause, ask your doctor. Knowing more about the drug’s side effects can help you and your doctor decide if it’s a good treatment option for you.

Here are a few questions you might want to ask:

  • Is my risk of side effects higher when I start taking nitrofurantoin?
  • How do the side effects of nitrofurantoin compare with other drugs to treat my condition?
  • Does nitrofurantoin cause any long-term side effects?
  • Are there any side effects I should tell you about right away?

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

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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.