Nitrofurantoin — a practical guide for bladder infections

Nitrofurantoin is a common antibiotic used mainly for uncomplicated bladder infections (cystitis). It works by attacking bacteria inside the urine and bladder. Doctors often pick it because it targets the urinary tract well and usually causes fewer gut and yeast problems than some broad-spectrum antibiotics.

How nitrofurantoin is used

For uncomplicated cystitis the usual prescription is nitrofurantoin monohydrate/macrocrystals (brand: Macrobid) 100 mg twice a day for 5 days. Another form, nitrofurantoin macrocrystals (sometimes called Macrodantin), is often given as 50–100 mg four times a day for 5–7 days. For prevention of repeat UTIs some doctors prescribe 50–100 mg at bedtime, but that’s a special case and needs close follow-up.

Take nitrofurantoin with food to help absorption and reduce stomach upset. Keep taking it for the full course even if symptoms improve after a day or two — stopping early can let the infection return or become resistant.

Side effects, warnings, and what to watch for

Common side effects are nausea, headache, and the harmless but noticeable brownish urine color. Less common but serious problems include lung reactions (new cough, shortness of breath), nerve damage (numbness or tingling in hands/feet), and liver injury. If you get new breathing problems, persistent cough, or tingling, stop the drug and contact a provider right away.

Avoid nitrofurantoin if you have severe kidney disease — generally if creatinine clearance is under about 30 mL/min it won’t reach effective levels in the bladder. Don’t give it to newborns or pregnant people at term (around delivery), and be cautious with anyone who has G6PD deficiency because of risk for hemolytic anemia.

Tell your prescriber about all medicines you take and any allergies. Some drugs and health conditions change how nitrofurantoin works or raise risks. If you’re unsure, ask your pharmacist — they can check interactions quickly.

Practical tips: keep fluids up while you have a UTI, don’t skip doses, and save the prescription info or pill bottle if you need to call your doctor. If symptoms don’t start to improve within 48–72 hours, or if you develop fever, back pain, or vomiting, seek medical care — the infection might be more serious or in the kidneys.

Want more detailed comparisons, brand info, or alternatives? Check trusted resources or talk to your healthcare provider for options tailored to your situation.