How To Use Nitrofurantoin
Nitrofurantoin is an antibiotic used to treat urinary tract infections (UTIs). Available in 50mg and 100mg capsules.
Key Takeaways
- Administration: Always take with food or milk to improve absorption and reduce stomach upset
- Treatment Duration: Typically 7 days for infections, longer for prevention
- Dosage: 50-100mg 4 times daily for infections; 50-100mg at bedtime for prevention
- Missed Dose: Take as soon as remembered unless close to next dose; never double dose
- Contraindications: Not for children under 3 months, late pregnancy, or severe kidney impairment
- Urine Changes: May turn dark yellow/brown - this is normal
How to Take Nitrofurantoin Correctly
Note: Nitrofurantoin may turn your urine dark yellow or brown. This is a normal effect of the medication and not a cause for concern.
Nitrofurantoin Dosage Guidelines
| Purpose | Adult Dosage | Duration | Special Notes |
|---|---|---|---|
| Treatment of UTI | 50-100mg capsule 4 times daily |
7 days | Continue full course even if symptoms improve |
| Prevention of recurrent UTIs | 50-100mg capsule at bedtime |
Long-term as prescribed | Monitor for side effects with prolonged use |
| Surgical prophylaxis | 50mg capsule 4 times daily |
Day of surgery + 3 days | Start on day of operation |
| Children (3 months+) | Based on weight: 5-7 mg/kg/day in divided doses |
As prescribed | Maximum 400mg/day Not for children under 3 months |
Special Populations
- Elderly patients: Use with caution; may require dose adjustment due to reduced kidney function
- Kidney impairment: Not recommended if eGFR <60 mL/min; contraindicated in severe impairment
- Pregnancy: Avoid during labour/delivery; use only if benefits outweigh risks in early pregnancy
- Breastfeeding: Avoid if baby has G6PD deficiency; consult doctor
Treatment Timeline & What to Expect
Medication begins to be absorbed; take with food to enhance bioavailability
Maximum antibiotic levels in urine achieved
Reduction in UTI symptoms like burning sensation and urgency
Significant reduction in pain, frequency, and urgency of urination
Finish full course even if symptoms have resolved to prevent recurrence
Important: If symptoms worsen or don't improve within 2-3 days, consult your healthcare provider as you may need a different antibiotic.
Managing Missed Doses
Tip: Set reminders on your phone or use a pill organizer to help maintain your dosing schedule.
Overdose: What to Do
- Seek immediate medical attention or call 111 for NHS advice
- Go to the nearest A&E department
- Take the medication packaging with you
Symptoms of Overdose
- Nausea and vomiting
- Dizziness or drowsiness
- Headache
- Confusion or disorientation
- Bluish skin discoloration (cyanosis)
There is no specific antidote for Nitrofurantoin overdose. Treatment is supportive and may include gastric lavage or activated charcoal if administered soon after ingestion.
Important Precautions When Using Nitrofurantoin
Before Starting Treatment
- Inform your doctor about any kidney problems
- Mention if you have G6PD deficiency (common in people of African, Mediterranean, or Asian descent)
- Disclose all medications you're taking, including supplements
- Report any history of lung disease or liver problems
During Treatment
- Avoid antacids containing magnesium trisilicate
- Limit alcohol consumption as it may increase side effects
- Be aware Nitrofurantoin may cause false-positive urine glucose tests
- Monitor for signs of lung problems (cough, shortness of breath)
Who Should Avoid Nitrofurantoin
- Infants under 3 months old
- People with severe kidney impairment (eGFR <30 mL/min)
- Individuals with known hypersensitivity to nitrofurans
- Pregnant women during labour or delivery
- Breastfeeding mothers if baby has G6PD deficiency
Potential Side Effects of Nitrofurantoin
- Difficulty breathing or shortness of breath
- Chest pain or palpitations
- Severe allergic reaction (swelling of face/lips, hives)
- Yellowing of skin/eyes (jaundice)
- Severe abdominal pain or persistent vomiting
Common Side Effects (affect up to 1 in 10 people)
- Nausea or loss of appetite
- Headache
- Dizziness or drowsiness
- Mild stomach discomfort
- Dark yellow or brown urine (harmless)
Less Common Side Effects
- Diarrhoea
- Cough or shortness of breath
- Skin rash or itching
- Fatigue or weakness
- Temporary hair loss
Rare But Serious Side Effects
- Lung inflammation or fibrosis
- Peripheral neuropathy (nerve damage)
- Liver inflammation (hepatitis)
- Severe blood disorders
- Autoimmune reactions
Frequently Asked Questions
Can I drink alcohol while taking Nitrofurantoin?
It's best to avoid alcohol while taking Nitrofurantoin. Alcohol may increase the risk of side effects like nausea, dizziness, and drowsiness. Additionally, alcohol can irritate the bladder, potentially worsening UTI symptoms.
What should I do if my urine turns brown?
Nitrofurantoin commonly causes urine to turn dark yellow or brown. This is a harmless side effect and not a reason to stop treatment. However, if you experience pain or other symptoms along with urine discoloration, consult your doctor.
How long does it take for Nitrofurantoin to work?
Most people notice improvement in UTI symptoms within 24-48 hours. However, it's essential to complete the full 7-day course even if you feel better sooner to ensure the infection is completely cleared and to prevent antibiotic resistance.
Can I take Nitrofurantoin if I'm pregnant?
Nitrofurantoin may be used during early pregnancy if benefits outweigh risks, but should be avoided during the last month (after 38 weeks) and during labour/delivery. Always consult your doctor before taking any medication during pregnancy.
Need Treatment for Urinary Tract Infection?
If you're experiencing symptoms of a urinary tract infection, our UK-registered doctors can help determine if Trimethoprim is appropriate for your condition after a thorough online consultation.
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Medical Content Manager
Nabeel is a co-founder and medical content manager of Chemist Doctor. He works closely with our medical team to ensure the information is accurate and up-to-date.
Medical Doctor
Dr. Feroz is a GMC-registered doctor and a medical reviewer at Chemist Doctor. He oversees acute condition and urgent care guidance.
Medical Director
Usman is a co-founder and medical director of Chemist Doctor. He leads the organisation's strategic vision, bridging clinical and operational priorities.
Review Date: 18 October 2025
Next Review: 20 March 2026
Published on: 18 October 2025
Last Updated: 19 October 2025
