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What is Macrobid (nitrofurantoin)?

Macrobid is a prescription antibiotic used to combat bacteria in the body. It is mainly used to treat urinary infections.

The drug works by entering the urine and removing bacteria present in the urinary tract.

Nitrofurantoin is the generic name of Macrobid. The medication comes as an oral capsule.

What is Macrobid used to treat?

Macrobid is specifically formulated to help prevent and treat urinary tract infections caused by certain types of bacteria.

To maintain the effectiveness of Macrobid and lessen the development of drug-resistant bacteria, you should take this medication when preventing or treating infections that are tested or firmly suspected to be caused by bacteria.

How do you take Macrobid?

Your doctor will prescribe a Macrobid dosage depending on:

  • The condition being treated

  • The severity of your infection

  • Your age

  • How you respond to the first dose

  • Your other medical conditions (if applicable)

Macrobid is available as a 100mg oral capsule (75mg nitrofurantoin monohydrate and 25mg nitrofurantoin macrocrystals).

Adults and children over the age of 12 should usually take one 100mg capsule every 12 hours for up to one week.¹

Take Macrobid capsules with food to avoid suffering from an upset stomach.

Always take this medication as instructed by your doctor.

Seeing results

You can determine if Macrobid is working if your urinary tract infection symptoms improve during the first few days of taking the medication.

You should start feeling better within three to five days² of starting nitrofurantoin treatment, although it may take a week before you feel completely better.

Make sure you finish the entire course of medication, even if your symptoms subside.

Potential side effects of Macrobid

You may experience side effects when taking Macrobid, including:

  • Indigestion

  • Drowsiness

  • Vomiting

  • Gas

  • Vaginal itching or discharge

  • Headache

  • Joint or muscle pain

  • Itching

  • Weakness

  • Nausea

  • Dizziness

  • Loss of appetite

  • Rash

Tell your doctor about any adverse effects that worsen or do not ease after a few days.

Macrobid may also bring about severe side effects, affecting the nervous system, lungs, liver, red blood cells, and gastrointestinal system. These may include:

  • Vision problems

  • Pale skin

  • Severe stomach pain

  • Chills

  • Bloody or watery diarrhea

  • Cough

  • Difficulty breathing

  • Ringing in the ears

  • Fever

  • Swollen glands

  • Tingling, numbness, or burning in the feet or hands

  • Weakness

  • Severe headache

  • Chest pain

  • Muscle aches

  • Severe pain behind the eyes

  • Vomiting or nausea

  • Swelling, redness, or pain in the lower jaw

  • Dizziness

  • Dark urine

  • Jaundice

Severe adverse effects of Macrobid may be more likely to occur in debilitated or sick patients or older adults.

You should seek medical assistance at once if you experience severe side effects.

Long-term use of Macrobid

For uncomplicated urinary tract infections, Macrobid is commonly given for seven days for male patients and five days for female patients.³

Macrobid may be taken for a longer period of time to prevent infections.

Rarely, chronic lung problems may occur with long-term use of nitrofurantoin (typically for six months or more). Discuss the risks and benefits of long-term treatment with your doctor.

Missed doses

If you miss a dose, take it as soon as you remember. However, skip the missed dose if it is nearly time to take the next dose.

Do not take a double dose to make up for the missed dose. Taking a double dose may cause severe side effects.


Macrobid overdose symptoms can include nausea, gastric irritation, and vomiting.

If you believe you or someone else has taken too much Macrobid, get emergency medical help right away.

What to discuss with your doctor before taking Macrobid

Before taking Macrobid, inform your doctor if you have been diagnosed with:

  • Diabetes

  • Kidney disease

  • Any debilitating disease

  • Vitamin B deficiency or electrolyte imbalance

  • Anemia

  • Liver disease

  • Glucose-6-phosphate dehydrogenase (G6PD) deficiency

Keep in mind that you should not use Macrobid if you have urination problems, severe kidney disease, liver problems, or a history of jaundice caused by nitrofurantoin.

You should also tell your doctor about any medications (over-the-counter or prescription), herbal medicines, or supplements you’re currently taking or plan to take.

Tell your doctor if you’re pregnant, breastfeeding, or planning to become pregnant during Macrobid treatment.

Stopping Macrobid

If you suddenly stop using Macrobid or don’t take it, your urinary tract infection is more likely to worsen or persist. For the best chance of success, continue taking the medication as prescribed by your doctor.

If you suddenly stop using Macrobid, the bacteria causing your urinary tract infection may become resistant to this antibiotic. As a result, the drug will no longer work effectively for you.

Macrobid and pregnancy

Macrobid is an FDA pregnancy category B³ medication, meaning it’s not expected to be harmful to an unborn baby during pregnancy. While there are no exhaustive studies about using Macrobid during pregnancy, many pregnant women have safely used this drug.

However, you should not take Macrobid if you are in the last two to four weeks of pregnancy. Macrobid can intervene with the undeveloped enzyme systems in your baby’s red blood cells, impairing the cells and potentially causing anemia.

Use this medication with caution when breastfeeding, as nitrofurantoin enters breast milk. Talk to your doctor to get their advice.

If you become pregnant while using Macrobid, inform your doctor immediately.

Interactions with other drugs

Macrobid can interact with other drugs and supplements. Interactions with other medicines may alter how Macrobid works or prevent it from working efficiently.

Tell your doctor about any other medications you’re currently using to help avoid potentially harmful interactions.

Some drugs that could cause interactions with Macrobid include:

  • Sulfinpyrazone and probenecid

  • Live typhoid vaccine

  • Live tuberculosis vaccine

  • Antacids that contain magnesium trisilicate

Allergy information

Macrobid can cause severe allergic reactions in some patients.

Possible symptoms of an allergic reaction include:

  • Swelling of the face, tongue, lips, or throat

  • Difficulty breathing

Seek emergency medical help if you or someone else develops these symptoms.

Don’t take Macrobid if you have had an allergic reaction to it in the past. Using this medication again could be life-threatening.

Clinical trial history

The first double-blind, randomized, placebo-controlled nitrofurantoin trial⁴ (1995–1996) found the drug significantly more effective than placebo for treating uncomplicated urinary tract infections.

78 women aged 15–54 participated in the trial. 40 received nitrofurantoin and 38 received a placebo.

After three days, 27 out of 35 (77%) patients in the nitrofurantoin group were reported to have combined symptomatic improvement and cure. In the placebo group, this number was 19 out of 35 (54%).

After seven days, improvement and cure were observed in 30 out of 34 (88%) patients treated with nitrofurantoin, and 17 out of 33 (51%) in the placebo group.

Tips and advice for taking Macrobid

The following tips and advice can help you take Macrobid safely and effectively:

  • Tell your pharmacist or doctor if you have had allergic reactions to any drugs, including nitrofurantoin. You should not take Macrobid if this is the case as you could experience a life-threatening allergic reaction.

  • Before taking the medication, inform your doctor about any other medical conditions you have, and your medical history.

  • Discuss any medications, supplements, herbs, and vitamins you’re taking with your doctor before using Macrobid. Some may interact with Macrobid and cause complications.

  • Take Macrobid precisely as instructed by your doctor.

  • Read the prescription label carefully before taking this drug.

  • Do not stop taking Macrobid before your prescription runs out or your doctor tells you to.

  • Take Macrobid with food to avoid having an upset stomach.

Curious about clinical trials?

Access the latest treatments and medications. unavailable elsewhere - entirely free of charge. We make it easy to take part.


Here at HealthMatch, we’ve done our best to ensure that the information provided in this article is helpful, up to date, and, most importantly, accurate.

However, we can’t replace the one-to-one advice of a qualified medical practitioner or outline all of the possible risks associated with this particular drug and your circumstances.

It is therefore important for you to note that the information contained in this article does not constitute professional medical or healthcare advice, diagnosis or recommendation of treatment and is not intended to, nor should be used to, replace professional medical advice. This article may not always be up to date and is not exhaustive of all of the risks and considerations relevant to this particular drug. In no circumstances should this article be relied upon without independent consideration and confirmation by a qualified medical practitioner.

Your doctor will be able to explain all possible uses, dosages, precautions, interactions with other drugs, and other potential adverse effects, and you should always talk to them about any kind of medication you are taking, thinking about taking or wanting to stop taking.

Curious about clinical trials?

Access the latest treatments and medications. unavailable elsewhere - entirely free of charge. We make it easy to take part.