Treat Uncomplicated Urinary Tract Infection With Nitrofurantoin

Nitrofurantoin is a first-line antibiotic for treating uncomplicated lower urinary tract infections (UTIs/cystitis) in women, as recommended by NICE. It is available as 50 mg and 100 mg capsules, with the modified-release formulation (Macrobid 100 mg) being the most commonly prescribed. Nitrofurantoin works by damaging bacterial DNA, and it achieves high concentrations in urine, making it particularly effective for bladder infections. Through the NHS Pharmacy First service, pharmacists can assess UTI symptoms and supply nitrofurantoin directly without a GP appointment.

Modified-release (Macrobid): 100 mg twice daily for 3 days (uncomplicated UTI in women). Standard release: 50 mg four times daily for 3 days, or 100 mg four times daily for 3 days for more severe infections. Take with food or milk to improve absorption and reduce nausea. The modified-release formulation is preferred due to twice-daily dosing and fewer gastrointestinal side effects. Complete the full 3-day course.

Nitrofurantoin is first-line because of very low bacterial resistance rates (less than 5% of UK E. coli isolates are resistant — compared to much higher resistance rates for trimethoprim). It concentrates in urine rather than blood, making it highly effective for bladder infections with minimal impact on gut bacteria. It has been used for decades with consistently low resistance, making it a cornerstone of UTI treatment.

Yes, the NHS Pharmacy First service allows pharmacists to assess UTI symptoms in women aged 16–64 and supply nitrofurantoin without a GP appointment. The pharmacist will ask about your symptoms, check for any red flag features requiring GP referral (such as fever, loin pain, or recurrent UTIs), and supply a 3-day course of nitrofurantoin if appropriate. This is a free NHS service.

Common side effects include nausea (reduced by taking with food), diarrhoea, and loss of appetite. The urine may turn dark yellow or brown — this is harmless. Uncommon side effects include headache, dizziness, and drowsiness. Rare but important side effects include pulmonary reactions (shortness of breath, cough — more common with long-term use) and peripheral neuropathy (tingling in hands/feet). Nitrofurantoin should not be used in patients with significant kidney impairment (eGFR <45 mL/min) as it will not achieve adequate urine concentrations.

Nitrofurantoin is not suitable for patients with significant renal impairment (eGFR below 45 mL/min), G6PD deficiency, or at term pregnancy (risk of neonatal haemolysis). It should not be used for upper urinary tract infections (pyelonephritis) as it does not achieve adequate blood levels. The pharmacist will check these before supplying. If nitrofurantoin is unsuitable, trimethoprim may be offered as an alternative.

Many women notice symptom improvement within 24–48 hours of starting nitrofurantoin. Burning and frequency should improve within the first day or two. Complete the full 3-day course even if symptoms resolve earlier, to ensure the infection is fully cleared. If symptoms are not improving after 48 hours, or if they worsen, return to the pharmacy or see your GP.