Nitrofurantoin (Generic Macrobid): Uses, Side Effects, Dosages, Contraindications, Warnings, Interactions & More

By Chesney Fowler, MD
Medically reviewed
April 21, 2021

Nitrofurantoin is an antibiotic used to treat infections of the urinary tract. While it’s best to talk to your healthcare provider if you have any questions about a medication, this article will provide some basics on this antibiotic, including how to take it, potential side effects and contraindications, and everything else to be aware of.

What Is Nitrofurantoin?

Nitrofurantoin is the generic name for an FDA-approved antibiotic sold under the brand names Macrobid, Macrodantin, and Furadantin. This prescription is usually taken in pill or capsule form. It works by killing the bacteria that cause urinary tract infections (UTIs) in the urethra, bladder, and/or kidneys. 

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What Is Nitrofurantoin Used For?

Nitrofurantoin serves one primary and important purpose: to kill the bacteria that cause UTIs. After taking it for several days in a row, UTI symptoms will start to subside. This is an indicator that your body has returned to its usual balance of healthy bacteria in your urinary tract.

Nitrofurantoin does not work against other bacterial infection such as sinus infections or strep throat. Nitrofurantoin does not treat any sexually transmitted infections (STIs). If you’re worried about STIs, you’ll need testing and different treatment.

What conditions can it treat? 

Nitrofurantoin is prescribed to treat UTIs, which fall into two major categories:

  • Lower tract UTIs: Also called bladder infections, these are the most common type of urinary tract infections and also the easiest to treat. They occur in the lower urinary tract, meaning the area from the urethra up to the bladder. 
  • Upper tract UTIs: These more serious forms of UTIs are also known as kidney infections. Upper UTIs usually result from untreated lower UTIs that spread upward to the kidneys. Symptoms include nausea, fever, body chills, and lower back or side pain. Kidney infections can be treated with antibiotics but in severe cases may require a trip to the hospital to prevent permanent organ damage or renal failure. 

Nitrofurantoin is primarily prescribed to treat uncomplicated lower urinary tract infections. A UTI is considered uncomplicated if someone has no urinary tract abnormalities or underlying health issues. If you are prone to recurrent UTIs—meaning you get two or more in six months or three or more in a year—your doctor might prescribe nitrofurantoin in a smaller dose over a longer period of time to prevent UTIs

Can You Get Nitrofurantoin Online?

While you need a doctor’s prescription to obtain nitrofurantoin, that doesn’t mean you need to set foot in a brick-and-mortar office to do so.

Services like K Health allow you to get your antibiotic prescription straight through your phone after scheduling an online consultation with a healthcare professional. If you use an online pharmacy to order medications, be sure the pharmacy is licensed.

What Forms Does Nitrofurantoin Come In?

Usually nitrofurantoin is taken as a capsule or a tablet. Children might be prescribed nitrofurantoin liquid, but this is not usually recommended for adults.

What Are Common Dosages of Nitrofurantoin?

To prevent or treat UTIs, doctors typically prescribe 50- or 100-milligram (mg) doses. Your prescription will have instructions from your doctor on how often to take the medication.

These will depend on how severe and symptomatic your UTI is. Typically, patients take nitrofurantoin one to four times a day for at least a week, but you may need the medication for a shorter or longer period of time depending on your specific situation. 

Side Effects 

Since nitrofurantoin is an antibiotic, it may affect your gut.

Antibiotics work by killing off the bad bacteria in your body. That inevitably means they kill some good bacteria as well. This can throw off the balance of bacteria in your gut microbiome, leading to nausea, vomiting, or loss of appetite.

This will go away on its own as the bacteria repopulates, so no need to panic, but it can be uncomfortable for a week or two. To speed the reintroduction of good bacteria into your gut, you may want to supplement with a probiotic under your doctor’s direction.

Nitrofurantoin may also turn your urine dark yellow or brown-ish color. 

How to Take Nitrofurantoin

Whether in capsule or liquid form, take your medication as prescribed. If it’s a pill, simply swallow it with a glass of water. For the liquid, measure out the appropriate dose with the provided measuring device. If you miss a dose, try to take the next dose as soon as you remember. If you miss multiple doses, contact your doctor. 

Nitrofurantoin can be kept at room temperature, so no need to refrigerate it unless you are specifically instructed to do so. 

Contraindications

Nitrofurantoin is safe for most people, including children who are at least one month old. However, if you fall into any of the below categories, tell your doctor before starting this prescription:

  • You are pregnant or breastfeeding
  • You have kidney disease or liver disease
  • You’re taking other antibiotics
  • You’re taking antacids that contain magnesium trisilicate
  • You’re taking an OTC remedy for cystitis or UTIs
  • You’re taking medication for gout

Lastly, people with a genetic condition called glucose-6-phosphate dehydrogenase (G6PD) deficiency should discuss using any antibiotic with their healthcare provider. People with G6PD deficiency are more susceptible to anemia (a lack of red blood cells), and sometimes their bodies can’t tolerate these medications.

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Warnings

In rare cases, nitrofurantoin can cause a potentially life-threatening allergic reaction or other serious side effects. If you notice any of the following, stop taking nitrofurantoin immediately and call your doctor.

  • Wheezing or trouble breathing
  • Tightness in the chest
  • Itchy, red, or pale skin
  • Swelling in the throat
  • Nausea, vomiting
  • Fainting, dizziness
  • Tingling or numbness in your fingers and toes
  • Muscle weakness
  • Excessive fatigue

How K Health Can Help

K Health provides a simple, accessible option for prescription treatment. Chat with a doctor on your phone to determine whether you need a prescription. Your doctor will then prescribe you medication, which can be picked up at a local pharmacy or shipped discreetly directly to you.

Frequently Asked Questions

What is nitrofurantoin used for?
Nitrofurantoin is a common antibiotic used for the treatment of urinary tract infections (UTIs). It’s sold under the brand names Macrobid, Macrodantin, and Furadantin.
How long does nitrofurantoin take to work for a UTI?
Your antibiotic should start working within three to five days, although it may take up to a week for symptoms to clear. Be sure to complete the full course of medication. That is the only way to ensure the infection completely goes away.
How long does nitrofurantoin stay in your system?
Nitrofurantoin stays in your body for about four to five hours.
What type of bacteria does nitrofurantoin kill?
Nitrofurantoin kills E. coli and other bacteria that lead to infections in the urinary tract.
K Health articles are all written and reviewed by MDs, PhDs, NPs, or PharmDs and are for informational purposes only. This information does not constitute and should not be relied on for professional medical advice. Always talk to your doctor about the risks and benefits of any treatment.

Chesney Fowler, MD

Dr. Fowler is an emergency medicine physician and received her MD from George Washington University. She completed her residency in emergency medicine at Christiana Care Health System. In addition to her work at K Health, Dr. Fowler is a practicing emergency medicine physician in Washington, DC.