Nitrofurantoin: uses, dosage and side effects
Nitrofurantoin is an antibiotic that concentrates in the urine and is used for uncomplicated urinary tract infection, and at a low nightly dose as long-term prevention in people with recurrent infections. It is prescription-only in Ireland. This page explains both uses, how it is taken, its side effects, and why a new infection is not a repeat prescription.
What nitrofurantoin is used for
Nitrofurantoin is used for uncomplicated urinary tract infection, meaning infection of the bladder rather than of the kidneys. It is unusual among antibiotics in that it is concentrated in the urine and reaches very little of the rest of the body, which is exactly why it works well in the bladder and is useless for an infection anywhere else, including a kidney infection or blood-borne infection. That same property is why it has remained effective against common urinary organisms while resistance rose elsewhere, and why guidelines across Europe keep it as a first choice for simple cystitis. A second, separate use is prevention: a low dose taken at night for months can reduce the frequency of recurrent urinary infections in selected people, a decision made by a GP or urology service after the pattern has been established.
Side effects of nitrofurantoin
The side effects listed in the product information include nausea, loss of appetite, vomiting, diarrhoea, headache and dizziness, and a harmless dark yellow or brown discolouration of the urine that alarms people who were not warned about it. Taking the dose with food reduces the nausea. Less common but important reactions involve the lungs, the liver and the nerves, and they are the reason long-term preventive use is monitored: seek medical advice for a new cough, breathlessness or chest tightness, for yellowing of the eyes or skin, or for new numbness or tingling in the hands or feet. Get urgent help for a spreading rash, blistering, swelling of the face or throat, or severe or bloody diarrhoea. Suspected reactions can be reported to the HPRA through its national system.
Dosage and how to take nitrofurantoin
The prescriber sets the dose and the length of treatment, and the two patterns are very different. Treatment of an acute bladder infection is a short defined course taken several times a day, and it is finished even once symptoms settle. Preventive use is a single low dose at night, continued for a period the prescriber decides and reviewed rather than repeated forever. Take nitrofurantoin with food or a glass of milk: it improves absorption and reduces stomach upset. Modified-release capsules are swallowed whole. Drink normally through a course. If a dose is missed, take it when you remember unless the next one is close, in which case skip it, and do not double up. Do not keep leftover capsules for a future episode, and never use someone else's.
Is nitrofurantoin prescription-only in Ireland?
Yes. Nitrofurantoin is prescription-only in Ireland; there is no over-the-counter version. What your pharmacist can offer for bladder symptoms is advice and symptomatic products, and a pharmacist will also tell you when the picture needs a doctor rather than a remedy. Prescriber control here is not bureaucratic: nitrofurantoin is unsuitable when kidney function is significantly reduced, is the wrong choice if the infection has reached the kidneys, and using an antibiotic for symptoms that turn out not to be an infection both fails to help and pushes resistance along. Seek medical assessment without delay if you have fever, shivering, back or flank pain, vomiting, blood in the urine, or if you are pregnant, male, or have a urinary catheter, since none of those is simple cystitis.
Continuing preventive nitrofurantoin and getting a repeat prescription
A new urinary infection is not a repeat prescription. New burning, urgency or lower abdominal pain needs assessment by a clinician who can test your urine, and our questionnaire is not a route to a first antibiotic course. One situation is different: if a GP or urology service in Ireland has already put you on low-dose nightly nitrofurantoin to prevent recurrent infections, the plan is unchanged and your supply is running low, you can ask a doctor to review a continuation through our online medical questionnaire. There is no video consultation and no phone appointment: you complete a structured medical questionnaire, a doctor reviews it, and if continuation is appropriate you receive a prescription document by email as a PDF laid out to the Annex of Directive 2012/52/EU. You bring it to any pharmacy with photo identification. There is no PIN code and no national identity number on it. The assessment costs 19,90 €. The fee covers the medical assessment, not the issuing of a document. If the doctor declines on medical grounds, the fee is refunded. If you do not supply the documentation the doctor asks for, the fee is not refunded. Expect questions about your kidney function results and the length of the course, because both decide whether continuing is reasonable.
Cost and reimbursement in Ireland
A short course of nitrofurantoin is normally an inexpensive prescription item, but what you pay depends on the preparation, the pack and the HSE arrangement covering you. Medical card holders receive prescribed items under the General Medical Services scheme with the charge that applies at the time. Everyone else can register with the HSE for the Drugs Payment Scheme, which caps what a person or family pays for approved prescribed items in a calendar month; that cap is worth understanding if you are on a preventive course month after month alongside other treatment. Ask your pharmacist what your prescription costs under your arrangement. Charges and thresholds are set by the HSE and change from time to time, so take the current figure from the HSE rather than from a commercial page, this one included.
Interactions and alcohol
Nitrofurantoin has fewer interactions than most antibiotics because so little of it circulates outside the urinary tract. Antacids containing magnesium trisilicate reduce its absorption and should be separated from the dose. Probenecid and sulfinpyrazone reduce how much nitrofurantoin is excreted into the urine, which lowers its effect where it is needed and raises levels elsewhere. Quinolone antibiotics and nitrofurantoin work against each other, so they are not combined. Nitrofurantoin can interfere with some urine glucose tests. Tell your pharmacist about everything you take, including supplements. Alcohol does not react with nitrofurantoin the way it does with metronidazole, and a drink does not stop it working, but alcohol irritates the bladder and adds to nausea, so most people find a short course easier without it.
Who should not take nitrofurantoin
Nitrofurantoin is not suitable when kidney function is significantly reduced, because too little reaches the urine to treat the infection while more remains in the body to cause harm. It is contraindicated in infants under three months of age and in people with glucose-6-phosphate dehydrogenase deficiency, because of the risk of haemolytic anaemia, and it is avoided at the end of pregnancy and during labour for the same reason. It is not used for kidney infection or suspected sepsis. Caution applies in anaemia, diabetes, electrolyte disturbance, vitamin B deficiency and debilitating illness, all of which increase the risk of nerve damage, and in existing lung or liver disease, particularly when treatment is long-term. Anyone who had a lung or liver reaction to nitrofurantoin before should not receive it again. The full list is in the leaflet.
Generic and brand names
Nitrofurantoin is the international non-proprietary name of the active substance and the name any European pharmacy recognises. In Ireland it is supplied under the substance name and under brand names, as capsules, tablets and an oral suspension, and in immediate-release and modified-release forms. The forms are not simply interchangeable, because they are dosed differently through the day, so the prescription specifies the preparation and the pharmacy dispenses that. If your pack differs from last time, check with the pharmacist that the form and strength match the prescription before the first dose. On a cross-border prescription the substance is written by its international name with the strength and pharmaceutical form, which is what allows an Irish pharmacy to read and dispense it correctly.
Pregnancy and breastfeeding
Nitrofurantoin is used in pregnancy in some circumstances, but not at the end of it: it is contraindicated at term and during labour, because of the risk of haemolytic anaemia in the newborn whose enzyme systems are still immature. Urinary infection in pregnancy is not a self-treated problem in any case; it carries risks for both mother and baby and needs assessment by your GP or maternity service, who will choose the antibiotic and check that the infection has cleared. During breastfeeding small amounts pass into milk, and it is avoided where the infant is under one month or has glucose-6-phosphate dehydrogenase deficiency. If you are pregnant, trying to conceive or breastfeeding, say so before any antibiotic is prescribed, and contact your maternity service rather than relying on a general page.
Patient information leaflet
The patient information leaflet in your pack is the authoritative document for the nitrofurantoin product you were given. It sets out the licensed indications, the strengths and forms, the full side effect list with frequency categories, the warnings about lung, liver and nerve reactions on longer use, and the note about urine discolouration that saves people an unnecessary fright. The HPRA publishes leaflets and the fuller summary of product characteristics for medicines authorised in Ireland, and the same documents are available through the Irish medicines information portal. Read the leaflet for your exact preparation, since immediate-release and modified-release products are dosed differently. Keep it with the pack until the course is finished, and follow it and your prescriber over anything you read online.
About this page
This page was written by the medical team at MEDINOW Sp. z o.o. and reviewed by lek. Damian Wojno, a doctor registered in Poland, PWZ no. 3211301. He holds a Polish licence to practise; he is not on the register of the Irish Medical Council, and this page does not suggest otherwise. Content verified on 29 August 2026 against the summary of product characteristics and the patient information leaflet published for the Irish market, and against public guidance from the HPRA and the HSE. This page is information, not advice for your particular case, and it is not an advertisement for a prescription medicine. Nothing here replaces an assessment by your own GP or a hospital clinician. If you are unwell and need urgent help, contact your GP, an out-of-hours service, or call 112 or 999.
Is nitrofurantoin prescription-only in Ireland?
Yes. There is no over-the-counter version in Ireland. A pharmacist can advise on symptoms and tell you when you need to be seen, but the antibiotic itself requires a prescription from an authorised prescriber.
How long does nitrofurantoin take to work?
Symptoms of a simple bladder infection usually begin to ease within the first day or two of starting treatment, and the course is still finished as prescribed. If you develop fever, shivering or back pain, or if symptoms have not improved by the end of the course, seek medical assessment, as that suggests the infection is not a simple one.
What are the common side effects of nitrofurantoin?
Nausea, loss of appetite, vomiting, diarrhoea, headache and dizziness are listed in the product information, along with a harmless dark discolouration of the urine. Taking it with food helps. New cough or breathlessness, yellowing of the skin or eyes, or tingling in the hands or feet need medical advice.
Can I drink alcohol while taking nitrofurantoin?
There is no reaction of the kind seen with metronidazole, and a drink does not stop nitrofurantoin working. Alcohol does irritate the bladder and adds to nausea, so most people find a short course more comfortable without it.
How do I get a repeat prescription for nitrofurantoin?
Only for a continuing preventive course. If an Irish GP or urology service already has you on low-dose nightly nitrofurantoin and the plan is unchanged, you can ask a doctor to review a continuation through our questionnaire for 19,90 €; the fee covers the assessment, is refunded if the doctor declines on medical grounds, and is not refunded if you do not supply the documentation requested. A new urinary infection is not a repeat and needs assessment.