Macrobid For Urinary Tract Infections: Effectiveness, Symptoms, Dosage, And Side Effects

Have you recently been diagnosed with a urinary tract infection (UTI) and prescribed Macrobid (nitrofurantoin)? You may want to learn more about the drug and why you’re taking it.

This article will provide all the information you need to understand your symptoms and infection, plus what to expect from Macrobid treatment.

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What causes a urinary tract infection?

The urinary tract is normally sterile, but bacteria can enter through the urethra (the tube that carries urine from the bladder to the outside of the body) and multiply in the bladder. This usually happens when there is a breakdown in the body’s natural defenses against infection.

E. coli is the most common culprit. It usually lives in the digestive tract. However, other bacteria can also cause UTIs. If the bacteria are not stopped at the bladder and travel up to the kidneys, this can lead to a kidney infection called pyelonephritis.

Anyone can get a UTI, but they are more common in women.

The following factors may increase your risk of developing a UTI:¹

Female anatomy

UTIs are much more common in women due to the female anatomy.

Women have a much shorter urethra than men, meaning bacteria have less distance to travel from outside the body to the bladder and kidneys.

Post-menopausal women are also more prone to UTIs because they produce less estrogen. This causes changes, such as vaginal dryness and weaker pelvic floor muscles.

Sexual activity

Sexually active people get more UTIs. This is because sex increases the risk of bacteria from outside the body entering the urinary tract.

Having a new sexual partner or using spermicide-based contraception also increase your risk.

It’s important to remember UTIs are not sexually transmitted infections (STIs). However, the bacteria involved in STIs, like gonorrhea, chlamydia, and syphilis, can also lead to UTIs and affect the sexual organs.

Enlarged prostate and prostate cancer

The prostate is a small gland in men that sits below the bladder and surrounds the urethra. It produces fluid that helps nourish and protect sperm.

As men age, the prostate can become enlarged (prostatic hyperplasia). This can cause urine retention in the bladder, raising the risk of UTIs. Having an enlarged prostate does not mean you have prostate cancer.

Prostate cancer is another risk factor for UTIs.

A study² found urinary catheterization was strongly linked to the occurrence of UTIs in people with enlarged prostates and prostate cancer.

Urinary catheter

A urinary catheter is a small plastic tube inserted into the bladder to drain urine. Catheters are commonly used during surgery or after an injury. They can also be used to treat certain long-standing urinary conditions, such as incontinence or blockages.

Catheters are generally safe but can increase your risk of developing a UTI. They are one of the most common causes of UTIs in a hospital setting,³, and the risk is higher with indwelling catheters. Indwelling catheters are those left in place continuously.

Urethral stricture

A urethral stricture is a narrowing of the urethra. It can block the flow of urine and cause UTIs. Injury, surgery, inflammation, or scar tissue formation can cause urethral strictures.

Being immunosuppressed

Taking immunosuppressive medications, or having diabetes and conditions that impair the body’s immune system, can lead to more bacterial infections in general, including UTIs.

UTI symptoms

The symptoms of a UTI can vary depending on the location of the infection. A UTI that affects the bladder (cystitis) may cause the following symptoms:

  • Cloudy or bloody urine

  • Fever between 98.7°F and 101°F (37.05°C and 38.3°C)

  • Urge to urinate more often than usual

  • Pain or burning sensation when urinating

A UTI that affects the urethra (urethritis) may cause the following symptoms:

  • Cloudy or bloody urine

  • Strong or foul-smelling urine

  • Difficulty urinating

  • Pain or a burning sensation when urinating

A UTI that affects the kidneys (pyelonephritis) may cause the following symptoms:

  • Fever above 101°F (38.3°C)

  • Nausea and vomiting

  • Pain in the side, back, or groin

  • Chills or shaking

  • Pain in the lower back, side, or groin

  • Cloudy or bloody urine

  • Foul-smelling urine

  • Frequent urination

  • Urgently needing to urinate

  • Difficulty urinating

Seek medical advice if you develop any of these symptoms. Untreated UTIs can lead to serious kidney infections that can be life-threatening.

A healthcare professional will usually ask about your symptoms and medical history. They may also order a urine test to look for bacteria, blood, or white blood cells in the urine. If the urine test results are positive, you may be given a course of antibiotics.

Sometimes, a healthcare provider may also order imaging tests, such as a CT scan or ultrasound, to look for signs of infection in the kidneys.

What is Macrobid?

Macrobid is the brand name for nitrofurantoin, a prescription-only drug. It comes as a 100mg oral capsule.

Nitrofurantoin is a type of antibiotic known as a urinary tract disinfectant. It works by preventing bacteria (usually E. coli, Klebsiella, Enterococci, and Staphylococcus aureus) from growing and multiplying in the urinary tract. The drug won’t affect bacteria growing in other parts of your body.

While the urinary tract includes the kidneys, ureters, and bladder, infections are usually found in the lower urinary tract consisting of the urethra and bladder. Bacteria can sometimes travel up to the kidneys, resulting in a more severe infection.

Macrobid is an effective antibiotic for most people, causing few side effects. However, as with all medications, this drug carries potential risks.

How effective is Macrobid (nitrofurantoin) for UTIs?

Your doctor may prescribe Macrobid to prevent or treat uncomplicated UTIs.

If your symptoms improve within the first few days of taking Macrobid, you can tell it’s working. You should start to feel better after three to five days.

You must keep taking your prescription until it runs out or your doctor tells you to stop, even if you feel better.

Some bacterial strains are resistant to nitrofurantoin. Your doctor may prescribe a different antibiotic if you have a recurrent UTI or your infection does not respond to Macrobid. 

If your UTI has progressed to a kidney infection, your antibiotic will also be changed because Macrobid has poor tissue uptake in the kidneys. Macrobid is still an effective antibiotic for most people with UTIs.

How to take Macrobid

Your doctor will prescribe a Macrobid (nitrofurantoin) dosage based on you and your infection. Always follow your doctor and pharmacist’s instructions carefully.

Typical dosage to prevent UTIs (adults and children over the age of 12)

Your doctor may recommend taking a single dose of 100mg after a trigger event (sexual intercourse, for example).

Alternatively, you may need to take a regular dose of 50 to 100mg at night. You would not usually be asked to take Macrobid for more than six months at a time.

Typical dosage to treat UTIs (adults and children over the age of 12)

The usual dose is 50 to 100mg twice a day for three to seven days. Take Macrobid with food.

Possible side effects of Macrobid

Macrobid is generally well-tolerated, but it can cause side effects in some people.

Common side effects

The most common side effects of Macrobid are:⁴

  • Nausea

  • Headache

  • Gas

Serious side effects

Macrobid comes with the following warnings of serious side effects:⁴ ⁵

Respiratory reactions

The Federal Drug Administration (FDA) warns Macrobid can cause respiratory reactions in some people.

Acute pulmonary reactions may occur within the first week of treatment. Your doctor will advise you to stop taking Macrobid immediately if you have a reaction like this.

Acute pulmonary reactions usually present as cough, difficulty breathing, chest pain, fever, and chills. It may cause fluid in the lungs (pulmonary infiltration with consolidation/pleural effusion) and excess white blood cells in the blood (eosinophilia).

Chronic pulmonary reactions are rare. You have a higher risk if you are older or have been taking Macrobid for at least six months. Seek medical help if you experience trouble breathing, a cough, or you generally feel unwell.

Liver problems

Macrobid may (rarely) cause liver problems, including hepatitis (inflamed liver), cholestatic jaundice, or hepatic necrosis.

Seek medical help if you experience intense itching, dark-colored urine, light-colored bowel movements, abdominal pain, nausea, weakness, or tiredness.

Neuropathy (nerve damage)

Rarely, Macrobid may cause damage to your peripheral nerves (peripheral neuropathy). This could cause you to feel pain, weakness, or numbness.

Macrobid may also cause optic neuritis (damage to your optic nerve), nystagmus, vertigo, dizziness, or drowsiness.

Clostridium difficile (C.diff)-associated diarrhea

Many antibiotics like Macrobid allow the bacteria Clostridium difficile (C.diff) to grow in the intestines. This could cause mild diarrhea or a more serious condition called pseudomembranous colitis.

Pseudomembranous colitis symptoms include:

  • Pain and cramps in your stomach

  • Diarrhea

  • Fever


Anemia occurs when your body does not produce enough red blood cells.

See your doctor immediately if you experience fatigue, weakness, pale skin, or shortness of breath.

Allergic reactions

Macrobid can cause serious allergic reactions.

Seek medical help immediately if you develop a swollen face, tongue, lips, or throat or if you have trouble breathing.

Stevens-Johnson syndrome

This is a rare but severe condition that can cause a blistering rash, fever, and difficulty breathing. Symptoms include joint pain, high temperature, sore throat, cough, and a rash. The rash may look like circular sores that are darker in the middle.

Many people who develop Stevens-Johnson syndrome also have a severe underlying illness. If you experience any of these symptoms, seek urgent medical attention.

Seek medical help if you develop symptoms of a more serious adverse reaction to Macrobid. Many of these serious side effects can be stopped by discontinuing the drug, so seeing a doctor as soon as you can is vital.

Does Macrobid interact with other medications?

Macrobid interacts with around 170 drugs. Taking Macrobid with other drugs could change how the drugs work or alter the amount of the drugs in your body. These interactions can be harmful, so you should never take medication without your doctor’s advice.

The following drugs can interact with Macrobid:

  • Other antibiotics, such as amoxicillin (Amoxil or Moxtag), ciprofloxacin (Cipro), and levofloxacin

  • Antacids

  • Vitamins and supplements

  • Heart rhythm medications, such as quinidine and procainamide

  • Seizure medications, such as phenytoin (Dilantin or Phenytek) and carbamazepine (Epitol, Carbatrol, Equetro, or Tegretol) 

  • Muscle relaxants, such as cyclobenzaprine (Amrix)

  • Drawing agents used to treat constipation, such as docusate

  • Water pills (diuretics)

This list is not exhaustive.

Remember to tell your doctor or pharmacist about any other medications (over-the-counter or prescription) you are currently taking or plan to start taking during Macrobid treatment.

I have another health condition — should I take Macrobid?

Tell your doctor or pharmacist about any other health conditions you have. They may make it dangerous for you to take Macrobid.

These conditions include:

  • Renal failure

  • Colitis

  • Diabetes

  • Glucose-6-phosphate dehydrogenase (G6PD) deficiency

  • Hepatotoxicity

  • Peripheral neuropathy

Can I take Macrobid while pregnant?

You must tell your doctor if you are pregnant, planning to become pregnant, or breastfeeding. It may not be safe for you to take Macrobid.

Your doctor will also need to know if you become pregnant while taking Macrobid. They may tell you to stop taking your medication.

Macrobid is an FDA pregnancy category B medication. It is not expected to harm an unborn baby during pregnancy, but research is limited.

Do not take Macrobid after 36 weeks of gestation. Macrobid could cause anemia in your baby, as it intervenes with the undeveloped enzyme systems in their red blood cells. It may also cause jaundice and increase the risk of kernicterus (a potentially fatal brain disorder) in your newborn.

Other treatment options for UTIs

If you are allergic to Macrobid, are pregnant, or have reduced liver or kidney function, you may need to take a different antibiotic to treat your UTI. These include:

  • Sulfonamides

  • Fluoroquinolones

  • Cephalosporins

  • Trimethoprim/sulfamethoxazole

  • Amoxicillin/clavulanate

When to see a doctor

Untreated urinary tract infections can lead to kidney infections, long-term kidney damage, or even kidney failure.

If you develop any UTI symptoms, make an appointment to see your doctor as soon as possible. Early diagnosis and treatment are critical to a successful outcome.

The lowdown

Macrobid is an effective antibiotic for urinary tract infections. The drug’s dosage and side effects may vary depending on the person taking it. You must follow your doctor’s instructions carefully and be aware of the risks and warnings associated with this medication.

Seek medical help right away if you experience a UTI symptom. There are many treatment options for UTIs, so please consult your doctor if you think you might have one.

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