Nitrofurantoin

Key facts

• Nitrofurantoin treats uncomplicated bladder infections only; it doesn't reach high enough levels in the blood or kidney tissue to treat a kidney infection.
• It's taken with food two to four times a day for three to seven days, and it can turn urine dark yellow or brown.
• Avoid it if your kidneys aren't working well, or from about 36 weeks of pregnancy onward: poor clearance lets it build up in the blood, and late pregnancy use risks a blood disorder in the newborn.
• Long-term or repeated use carries a rare risk of lung scarring or liver damage; seek urgent care for new breathlessness, a persistent cough, or yellowing skin.

What Nitrofurantoin treats

Nitrofurantoin treats uncomplicated cystitis, a lower urinary tract infection, and is sometimes used as a long-term, low-dose preventive for recurrent bladder infections under specialist direction. It's not appropriate for kidney infections, a suspected bloodstream infection, or prostate infections.

How Nitrofurantoin works

Nitrofurantoin is filtered by the kidneys and concentrates in the urine, where it's activated inside bacterial cells. The activated drug damages several bacterial systems at once, including DNA, cutting off multiple survival pathways, which is why resistance to it develops slowly.

Before you take it

• Do not take nitrofurantoin if you have significantly reduced kidney function; it can't reach effective levels in urine, and toxic levels build up in the blood instead.
• Avoid it from around 36 weeks of pregnancy through labour and delivery, it can cause a red blood cell disorder in the newborn.
• Tell your prescriber about G6PD deficiency, a red blood cell condition that raises the risk of anaemia with this drug.
• Tell your prescriber if you've had a previous lung or liver reaction to nitrofurantoin.

Side effects

Nausea and headache are common; urine may turn darker.

Stop and seek urgent medical care for any of these:

• New breathlessness, a persistent cough, or fever, especially after weeks of use.
• Yellowing of the skin or eyes, or dark urine with pale stools.
• Numbness or tingling in the hands or feet.
• Hives, facial swelling or difficulty breathing.

Safety essentials

• Nitrofurantoin is for lower urinary tract infections only; if you develop back pain, fever or feel generally unwell, tell your prescriber, this may be a kidney infection needing a different antibiotic.
• Avoid it with significantly reduced kidney function and in late pregnancy, from about 36 weeks, both raise the risk of harm.
• If you're on long-term low-dose prevention, have periodic checks for lung and liver problems, rare but serious effects that build up over months of use.
• Finish any treatment course exactly as directed; stopping early or reusing leftover doses adds to antibiotic resistance.

This page is educational and does not replace advice from a doctor or pharmacist who knows your health history.