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Nitrofurantoin is an antibiotic that concentrates in urine and treats selected uncomplicated lower urinary tract infections. It is activated inside bacterial cells by bacterial nitroreductases (NfsA and NfsB), which reduce the nitro group to produce reactive intermediates that damage DNA, RNA, protein synthesis, and the Krebs cycle — a multi-target mechanism that makes acquired resistance uncommon. It is not suitable for suspected kidney infection, and a doctor screens for that before prescribing it.
Form: tablet or capsule · Frequency: usually multiple daily doses · Status: prescription only · Results: symptoms should begin easing within days.

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What it is

Nitrofurantoin is a prodrug: bacterial nitroreductases (NfsA and NfsB) reduce its nitro group to highly reactive intermediates that attack multiple bacterial targets — the ribosome (protein synthesis), the citric acid cycle, DNA and RNA synthesis, and cell wall assembly. Because it damages several essential processes at once, a bacterium must acquire multiple independent mutations to become resistant, which is why resistance has remained rare after seven decades of clinical use. It targets susceptible bacteria in the lower urinary tract, at the concentrations it reaches in urine.

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Dose and course

Regimens vary by immediate- or modified-release formulation, so the exact schedule depends on the product prescribed — the doctor selects the formulation, frequency and duration rather than using a single generic schedule.
A common prolonged-release regimen is 100 mg twice daily for a product-specific course; immediate-release products may use a different frequency. It is normally taken with food or milk, which improves absorption and tolerance, and the full prescribed course should be completed — use the same formulation throughout rather than substituting schedules.
1

Assessment

Confirm a lower, uncomplicated UTI is likely. Fever, flank pain and systemic illness prompt a different care route.
2

Course

Take each dose with food or milk, as prescribed, spaced evenly.
3

Review

Escalate persistent, worsening or systemic symptoms rather than continuing unchanged.

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What has been reported

Rare but serious reactions can involve the lungs, liver, nerves or a severe allergic response: new cough, breathlessness, fever, chest pain, yellow skin or eyes, numbness, tingling, weakness, or a severe rash need prompt assessment.

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Who it is not suitable for

  • You may have pyelonephritis (kidney infection) or a systemic infection
  • Your estimated creatinine clearance is below 30 mL/min — nitrofurantoin concentrates in urine only when kidneys excrete it adequately; at low clearance, urinary concentrations fall below the therapeutic range while systemic levels rise, increasing the risk of peripheral neuropathy. This is a pharmacokinetic contraindication: the medicine cannot reach effective urinary concentrations when glomerular filtration is substantially impaired, so the balance of risk exceeds any likely benefit
  • You are in the third trimester of pregnancy or breastfeeding a baby with glucose-6-phosphate dehydrogenase (G6PD) deficiency
  • You previously had a serious lung, liver, or nerve reaction to it

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Contact your doctor if

  • Fever with flank or back pain, vomiting, confusion, pregnancy, or feeling acutely unwell
  • New breathing symptoms, jaundice, severe rash, numbness, tingling, or weakness — stop and seek prompt advice
  • Symptoms worsen, fail to improve within 2–3 days, or return after the course
For emergencies — severe, sudden or unexpected symptoms — call your local emergency number or go to the nearest emergency department, then let your doctor know through your account chat. Related option: fosfomycin, another antibiotic used for uncomplicated lower UTIs.

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How Hi-Doctor handles it

An EU-licensed doctor reads your questionnaire and answers within 24 hours. If the doctor decides it is not safe to prescribe, the consultation fee is refunded in full. Follow-up happens in the private chat inside your account. See how the consultation works, how we handle safety and eligibility, and pricing. For the underlying condition, see urinary tract infection.

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Sexual health consultation

Answer the sexual health questionnaire and a registered doctor reviews it. They decide whether treatment is appropriate, which one, and at what dose — and declining is a normal outcome. See what it costs and how the review works.
This page is reference information, not medical advice and not a prescription. Whether a medicine is appropriate for you is decided by a registered doctor after reviewing your consultation.