Nitrofurantoin Pediatric Dose Calculator
Weight-based nitrofurantoin dosing for children, with maximum doses, age limits and sources. Enter age and weight for the dose in mg and syrup mL or capsules.
Pediatric dosing
Acute lower urinary tract infection (cystitis)
Recurrent UTI prophylaxis (selected children, specialist advice)
Nitrofurantoin dose chart by age and weight
Acute lower urinary tract infection (cystitis). Weights are WHO/IAP reference medians for age — always dose on the measured weight.
| Age | Weight | Dose (mg) | Suspension 25 mg/5 mL | Frequency |
|---|---|---|---|---|
| 3 months | 6.1 kg | 9.15 mg | 1.8 mL | Four times daily with food or milk |
| 6 months | 7.6 kg | 11.4 mg | 2.3 mL | Four times daily with food or milk |
| 9 months | 8.6 kg | 12.9 mg | 2.6 mL | Four times daily with food or milk |
| 1 year | 9.3 kg | 14 mg | 2.8 mL | Four times daily with food or milk |
| 18 months | 10.6 kg | 15.9 mg | 3.2 mL | Four times daily with food or milk |
| 2 years | 11.8 kg | 17.7 mg | 3.5 mL | Four times daily with food or milk |
| 3 years | 14.1 kg | 21.1 mg | 4.2 mL | Four times daily with food or milk |
| 4 years | 16.2 kg | 24.3 mg | 4.9 mL | Four times daily with food or milk |
| 5 years | 17.5 kg | 26.3 mg | 5.3 mL | Four times daily with food or milk |
| 6 years | 19 kg | 28.5 mg | 5.7 mL | Four times daily with food or milk |
| 8 years | 24.4 kg | 36.6 mg | 7.3 mL | Four times daily with food or milk |
| 10 years | 31.1 kg | 46.7 mg | 9.3 mL | Four times daily with food or milk |
| 12 years | 39.4 kg | 50 mg | 10 mL | Four times daily with food |
Strengths in the calculator
- Suspension 25 mg/5 mL (Oral)
- Capsule/tablet 50 mg (Oral)
- Capsule/tablet 100 mg (Oral)
- Modified-release capsule 100 mg (twice-daily form) (Oral)
Different strength on your bottle? Use “Different strength on the bottle?” under the result.
Safety
Contraindications and cautions
- eGFR below 45 mL/min/1.73 m² (ineffective, more toxicity); G6PD deficiency (haemolysis); infants under 3 months.
- Stop if breathlessness, cough, jaundice or numbness develops.
Pregnancy and breastfeeding
Legacy FDA category B. Used for UTI in pregnancy but avoid at term (36–42 weeks) and in labour — risk of neonatal haemolysis.
Avoid if the infant is under 1 month old or G6PD deficient.
Clinical notes
Brown discolouration of urine is harmless. Give with food to reduce nausea. Liquid availability varies by country — check local stock.
Adult and adolescent (≥40 kg) dose
50 mg four times daily, or 100 mg modified-release twice daily — Modified-release twice daily for 3 days (5–7 days in men) (max 100 mg per dose).
Other names and brands
- USA: Furadantin, Macrobid, Macrodantin
- UK: Macrobid, Macrodantin
Brand examples only — products and strengths vary by country. Always check the label.
Frequently asked questions
What is the nitrofurantoin dose for children?
Acute lower urinary tract infection (cystitis): <12 years: 1.25–1.75 mg/kg/dose · four times daily with food or milk · max 100 mg/dose; ≥12 years: 50 mg per dose · four times daily with food. Usual duration: 3–5 days. Always use the child's measured weight and check the strength on the bottle.
How many mL of suspension 25 mg/5 mL for an 11.8 kg child?
For acute lower urinary tract infection (cystitis), an 11.8 kg child (about 2 years) needs 17.7 mg per dose — 3.5 mL of Suspension 25 mg/5 mL, four times daily with food or milk. Recalculate with the child's actual weight.
From what age can nitrofurantoin be given?
Age range in PediaRx: ≥3 months. The calculator does not calculate a dose below 3 months. Each indication can have its own age and weight limits, shown with its regimen.
Is nitrofurantoin safe in pregnancy?
Legacy FDA category B. Used for UTI in pregnancy but avoid at term (36–42 weeks) and in labour — risk of neonatal haemolysis.
Sources and editorial process
- BNF for Children — Nitrofurantoin — NICE / BMJ Group / Royal Pharmaceutical Society
- Urinary tract infection (lower): antimicrobial prescribing (NG109) — National Institute for Health and Care Excellence
- Furadantin (nitrofurantoin oral suspension) — US prescribing information — DailyMed (U.S. National Library of Medicine)
Dosing data last updated 2026-09-28. PediaRx is built and maintained by Dr. Shounak Pal, MBBS (Medical Officer, Government of West Bengal, India — founder and developer of PediaRx). Every regimen is encoded with explicit units, maximum doses and age/weight limits and is checked by automated tests before publication. Report an error: hello@pediarx.com.
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Clinical disclaimer: reference tool for qualified health professionals. Verify every dose against current guidance and the product label before prescribing.
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