Nitrofurantoin monitoring

Before starting

Consider

• Baseline
  • Estimated glomerular filtration rate · if long-term prophylaxis or renal impairment suspected
  • Glucose-6-phosphate-dehydrogenase deficiency · contraindicated if deficiency
  • Liver function tests · if long-term prophylaxis
  • Porphyria · contraindicated

Interpreting renal function

Contraindicated if eGFR is less than 45mL/minute/1.73m². Risk of peripheral neuropathy and treatment may not be effective due to inadequate urine concentrations.
May be used with caution if eGFR 30 to 44 mL/min/1.73m² as a short course only (3 to 7 days) to treat uncomplicated lower urinary tract infection caused by suspected or proven multi-drug resistant bacteria where benefit outweighs risk.

Continued until stable

Consider

• Periodically
  • Estimated glomerular filtration rate · long-term prophylaxis contraindicated if less than 45mL/minute/1.73m²
  • Liver function tests · cholestatic jaundice can occur with short-term (usually up to 2 weeks) therapy
  • Pulmonary symptoms · New or worsening. May occur with short- or long-term use. Increased vigilance for acute pulmonary reactions needed in first week of therapy, especially important in elderly

Ongoing once stable

Consider

• Periodically
  • Estimated glomerular filtration rate · long-term prophylaxis contraindicated if less than 45mL/minute/1.73m²
  • Liver function tests · chronic active hepatitis, occasionally leading to hepatic necrosis, is possible with any duration but particularly with long-term prophylaxis (usually after 6 months)
  • Pulmonary symptoms · especially important in elderly

Abnormal results

Pulmonary toxicity

Stop nitrofurantoin immediately at the first signs of pulmonary symptoms, such as breathlessness and cough. Acute reactions tend to occur in the first week of therapy and are reversible with cessation. Chronic pulmonary reactions (including pulmonary fibrosis) can develop gradually and cause permanent injury if not detected early, even after cessation of therapy.

Hepatotoxicity

Stop nitrofurantoin immediately at first signs of hepatotoxicity. Onset of hepatitis may be gradual.

Haematological toxicity

Stop nitrofurantoin if any otherwise unexplained haematological disorder occurs.

Neurological toxicity

Stop nitrofurantoin immediately at the first signs of peripheral neuropathy (paraesthesia) or if any otherwise unexplained neurological syndromes occur

Urinary effects

People taking nitrofurantoin are susceptible to false positive urinary glucose (if tested for reducing substances).

Notes

Advice to patients

Advise patients to seek immediate medical advice if they develop any signs or symptoms of:

• respiratory toxicity, such as, cough, chest pain or shortness of breath
• fever and chills
• hepatotoxicity, onset can be gradual and non-specific, such as, nausea, rash, headache or flu-like symptoms
• peripheral neuropathy (sensory as well as motor involvement)
• haemolysis

Bibliography

• British National Formulary (online) London: BMJ Group and Pharmaceutical Press [cited 16/12/2025]
• Medicines and Healthcare products Regulatory Agency. Nitrofurantoin: reminder of the risks of pulmonary and hepatic adverse drug reactions – GOV.UK. Drug Safety Update, April 2023 [cited 16/12/ 2025]
• Advanz Pharma. Summary of Product Characteristics – Nitrofurantoin 100mg Capsules. Last revised 19/08/2025 [cited 16/12/2025]
• NICE Clinical Knowledge Summaries (CKS). Urinary tract infection – lower (women). Last revised Feb 2025 [cited 19/12/2025]
• National Institute for Health and Care Excellence (NICE). Urinary tract infection (recurrent): antimicrobial prescribing. Last updated Dec 2024 [cited 19/12/2025]
• National Institute for Health and Care Excellence (NICE). Urinary tract infection (lower): antimicrobial prescribing. Last updated Oct 2018 [cited 19/12/2025]

Update history