Got a simple bladder infection and your doctor mentioned nitrofurantoin? This page tells you what nitrofurantoin does, how people usually take it, what to watch for, and when it isn’t a good choice. No fluff—just the facts you need to make sense of the medicine and stay safe.
Nitrofurantoin is an antibiotic mainly used for uncomplicated lower urinary tract infections (cystitis). It works by damaging bacteria’s ability to make essential proteins and DNA, which stops the infection. It’s most useful when the infection is limited to the bladder—nitrofurantoin doesn’t reach high levels in the bloodstream, so it’s not the right pick for kidney infections (pyelonephritis) or sepsis.
Typical dosing depends on the formulation. For the common combination called Macrobid (nitrofurantoin monohydrate/macrocrystals), the usual adult dose is 100 mg twice daily for five days for uncomplicated cystitis. Other nitrofurantoin products (macrocrystals like Macrodantin) may be dosed 50–100 mg four times daily for 5–7 days. Always follow your prescriber. Take it with food to reduce stomach upset and help absorption.
Most people tolerate nitrofurantoin fine, but watch for these issues. Common side effects: nausea, loss of appetite, headache, and dark or brown urine (this is harmless but can be surprising). More serious but less common problems include:
Kidney function matters. Nitrofurantoin is not recommended when kidney function is poor—most clinicians avoid it if creatinine clearance is very low (for example under 30 mL/min). It’s also not recommended for newborns (risk of hemolysis) and generally avoided at term in pregnancy without specific guidance from your doctor.
Drug interactions are limited, but always tell your prescriber about all medicines and supplements you take. If symptoms don’t improve in 48–72 hours or you develop fever, flank pain, or worsening symptoms, contact your healthcare provider—this could mean a more serious infection that needs a different antibiotic.
Practical tips: finish the full course even if you feel better, take doses with food to reduce nausea, and save packaging or prescriptions if you have repeated UTIs so your provider can check past treatments. If you’ve had bad reactions to antibiotics before, note them in your medical record.
If you have questions about a prescription or whether nitrofurantoin is right for you, ask your pharmacist or doctor. They can confirm dose, duration, and safety based on your health history.
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