Nitrofurantoin: what it treats, how to take it, side effects
Last updated September 3, 2026.
Nitrofurantoin is an antibiotic used specifically for urinary tract infections. You may know it as Macrobid or Macrodantin. The label calls it an antibacterial agent specific for UTIs - it concentrates in the urine, which makes it a precision tool for bladder infections and the wrong tool for infections elsewhere.
What does it treat?
Urinary tract infections, and that is the job. It kills the bacteria that cause UTIs. Like all antibiotics it does nothing for colds, flu, or other viral infections, and because it works in the urine rather than the blood and tissues, it is not used for kidney infections or infections in other parts of the body.
How do you take it?
With food, at the same times each day. MedlinePlus gives the general pattern - two or four times a day for at least 7 days - and the Macrobid label gives the standard adult course: one 100 mg capsule every 12 hours for 7 days. The food is part of the instructions, not a suggestion; it helps the drug absorb and softens stomach upset. Shake the liquid form well and measure it with a dosing spoon or cup. You should feel better within the first few days. Finish the whole prescription, and if you miss a dose take it when you remember unless the next one is close, spacing the day's remaining doses evenly - never double up.
Side effects to know
- Common: nausea, vomiting, loss of appetite, heartburn or gas, headache, and hair loss.
- Serious: lung reactions - fever, chills, chest pain, a persistent cough, or difficulty breathing need immediate attention. Nerve problems show up as numbness, tingling, or a pinprick feeling in the fingers and toes, or muscle weakness. Liver problems look like yellowing skin or eyes, dark urine, fatigue, and pain in the upper right stomach. Also serious: confusion, dizziness, paleness, severe watery or bloody diarrhea, and allergic reactions with facial swelling or trouble swallowing.
Who should not take it?
If you have ever had kidney disease, or jaundice or other liver problems while taking nitrofurantoin before, your doctor will probably tell you not to take it. It should not be taken during the last month of pregnancy because it can cause problems in newborns after delivery - if you are pregnant or planning pregnancy, that sets the timing conversation. Flag anemia, diabetes, lung problems, nerve damage, electrolyte imbalances, low vitamin B levels, and G6PD deficiency. Antacids interact with it, so mention those too.
When is it an emergency?
Call 911 or get emergency care for trouble breathing or swallowing, swelling of the face, mouth, lips, or throat, and for chest pain with fever and cough - lung reactions to this drug can escalate. New numbness or tingling in your hands and feet, or yellowing skin or eyes, means calling your doctor immediately. For an overdose, call Poison Control at 1-800-222-1222. Pymander's escalation routing is built and tested specifically for this class of decision; see the safety architecture working paper.
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Common questions
Why do I have to take nitrofurantoin with food?
MedlinePlus builds food into the dosing instructions - nitrofurantoin is usually taken with food, two or four times a day. Food helps your body absorb the drug and blunts the nausea that tops its common side effect list. Taking it on an empty stomach gets you the side effects with less of the benefit.
Why is nitrofurantoin only used for UTIs?
Because of where it goes. The label describes it as an antibacterial agent specific for urinary tract infections: it concentrates in the urine, where bladder infections live, instead of building useful levels in blood or other tissues. That focus is what makes it effective for UTIs and unsuitable for infections anywhere else.
How fast does nitrofurantoin work?
MedlinePlus says you should begin to feel better during the first few days of treatment. If the burning and urgency are not improving or are getting worse by then, call your doctor - the bacteria may be resistant.
Can I take antacids with nitrofurantoin?
Not without checking. MedlinePlus flags antacids as a product that may interact with nitrofurantoin and says not to start them while taking it without discussing with your healthcare provider. If heartburn is already a side effect you are feeling, tell your doctor rather than self-treating it.
What is the deal with the lung warning?
Nitrofurantoin can occasionally inflame the lungs. MedlinePlus's get-help list includes fever, chills, chest pain, persistent cough, and difficulty breathing or swallowing. These can come on suddenly during a course or slowly with long-term use - either way, they mean calling your doctor immediately, not finishing the bottle first.
Can I drink alcohol while taking nitrofurantoin?
Neither the FDA label nor MedlinePlus lists a specific alcohol interaction for nitrofurantoin. Alcohol can worsen nausea and irritate the bladder while you are treating a UTI, so many clinicians suggest skipping it during the course - ask your doctor about your situation.