Synopsis
Choose an antimicrobial only when its expected benefit justifies treatment, prescribe an infection-specific regimen and reassess the diagnosis, route and duration as evidence develops.
- Establish the infection site and severity before choosing an antimicrobial or interpreting a positive sample.
- Check allergy phenotype, pregnancy possibility, recent antibiotics, previous susceptibility results, renal function and interactions.
- Use an infection-specific regimen with route, dose, interval and total course documented from the start.
Key red flags
Fever, flank pain or systemic deterioration in a patient treated for lower UTI requires reassessment for upper-tract or complicated infection; a bladder-directed regimen may be inadequate.
Investigation priorities
Define the suspected syndrome and identify immediate physiological risk.
Management branches
A 32-year-old non-pregnant woman has dysuria and frequency without vaginal symptoms, fever or flank pain. She is stable, can take oral medicine, has eGFR 82 mL/min/1.73 m² and no relevant allergy, G6PD deficiency or recent resistant isolate.
- Confirm that the findings fit lower urinary infection and do not suggest a different diagnosis or upper-tract disease. Discuss immediate versus back-up treatment according to symptom burden, complication risk and preference; make the observation and escalation plan explicit.
- If immediate treatment is chosen, nitrofurantoin is a NICE first-choice option for this setting. Select the modified-release preparation and prescribe the complete three-day regimen shown in the prescribing section; the formulation determines the dosing interval.
Key medicines
Nitrofurantoin for uncomplicated lower UTI in non-pregnant adult womenNICE NG109 regimen: 100 mg modified-release orally twice daily for 3 days when eGFR is at least 45; if that formulation is unavailable, 50 mg orally four times daily for 3 days.Take with food or milk. Exclude upper-tract infection; avoid G6PD deficiency, previous nitrofurantoin liver injury and relevant hypersensitivity. Pregnancy and eGFR below 45 require a different individual assessment; stop and investigate new respiratory or hepatic symptoms.
Doxycycline when antibiotics are indicated for adult acute coughNICE NG120: 200 mg orally on day 1, then 100 mg orally once daily for 4 further days, giving a 5-day course in total.Avoid in pregnancy; review interactions and administration instructions, including swallowing with water while upright and separating relevant mineral-containing products according to product advice.