Nitrofurantoin is an antibiotic.

It's used to treat urinary tract infections (UTIs), including cystitis and kidney infections.

When you take nitrofurantoin, your body quickly filters it out of your blood and into your pee. This is useful if you have a urinary tract infection because it means the medicine is concentrated at the site of infection. But it means nitrofurantoin won't work for any other types of infection.

Nitrofurantoin is available on prescription. It comes as capsules, tablets and a liquid that you drink.

• The most common side effect of nitrofurantoin is an upset stomach. Taking this medicine with or straight after food will help prevent a stomach upset.
• You'll feel better within a few days for most infections.
• You can drink alcohol while taking nitrofurantoin.
• Nitrofurantoin may turn pee dark yellow or brown. This is quite normal. Pee will return to normal after you finish taking the medicine.
• Nitrofurantoin is also called by the brand names Aratoin, Macrobid, Macrodantin and Furadantin.

Nitrofurantoin can be taken by adults including pregnant and breastfeeding women.

Nitrofurantoin isn't suitable for everyone. To make sure it's safe for you, tell your doctor if you have:

• ever had an allergic reaction to nitrofurantoin or any other medicines in the past
• either of the rare inherited conditions: porphyria (a blood disorder) or glucose-6-phosphate dehydrogenase (G6PD) deficiency
• severe kidney disease
• diabetes
• any illness causing severe weakness
• anaemia or vitamin B deficiency

The usual dose of nitrofurantoin to treat a urinary tract infection is either 100mg taken twice a day or 50mg taken 4 times a day. Severe infections may need a higher dose of 100mg taken 4 times a day.

The usual dose of nitrofurantoin to prevent a urinary tract infection is 50mg to 100mg once a day at night.

Try to space your doses evenly throughout the day. If you're taking nitrofurantoin twice a day, leave 12 hours between each dose - for example, at 8am and 8pm. If you're taking it 4 times a day, this will usually be first thing in the morning, at about midday, late in the afternoon, and at bedtime.

Generally, it's better to take nitrofurantoin with a meal or snack. This helps prevent a stomach upset.

How to take it

Swallow nitrofurantoin tablets and capsules whole. Do not chew or break them.

There's a liquid nitrofurantoin for people who find it difficult to swallow tablets.

If you're taking nitrofurantoin as a liquid, it'll usually be made up for you by your pharmacist. The medicine will come with a syringe or spoon to help you take the right amount. If you don't have a syringe or spoon, ask your pharmacist for one. Do not use a kitchen teaspoon as it will not give the right amount.

The dose of nitrofurantoin you need to take depends on whether it's being used to treat or prevent a urinary tract infection, your age, and how bad the infection is.

How long will I take it for?

If you're taking nitrofurantoin to treat a urinary tract infection, then you usually need to take it for 3 to 7 days.

If you're taking nitrofurantoin to stop urinary tract infections coming back, you may need to take it for several months.

If you're taking nitrofurantoin to prevent an infection before having surgery, you'll usually need take it on the day of the operation and for the next 3 days.

What if I forget to take it?

If you forget to take a dose, take one as soon as you remember, unless it's nearly time for your next dose. In this case, just leave out the missed dose and take your next dose as normal.

Never take 2 doses at the same time. Never take an extra dose to make up for a forgotten one.

If you often forget doses, it may help to set an alarm to remind you. You could also ask your pharmacist for advice on other ways to help you remember to take your medicine.

What if I take too much?

Taking an extra dose of nitrofurantoin by accident is unlikely to harm you.

Talk to your pharmacist or doctor if:

• you're worried or get severe side effects
• you've taken more than 1 extra dose

Like all medicines, nitrofurantoin can cause side effects, although not everyone gets them.

Common side effects

These common side effects of nitrofurantoin happen in more than 1 in 100 people. Keep taking the medicine, but talk to your doctor if these side effects bother you or don't go away:

• feeling sick (nausea)
• being sick (vomiting) and diarrhoea
• loss of appetite
• headaches
• dizziness or feeling sleepy

Nitrofurantoin may cause your pee to turn dark yellow or a brownish colour. This is normal and not a reason to stop taking the medicine. Your pee will return to normal once you stop taking nitrofurantoin.

Serious side effects

Serious side effects are rare and happen in less than 1 in 1,000 people.

Call a doctor straight away if you get:

• pains in the chest, difficulty breathing, coughing, chills, or a high temperature (38C or above)
• pale poo and dark pee together, yellow skin or the whites of your eyes turn yellow - this can be a sign of liver or gallbladder problems
• pins and needles, tingling sensations, numbness or weakness - these can be signs of nerve problems
• bruising or bleeding you can't explain (including nosebleeds), sore throat, a high temperature (38C or above) and feeling tired or generally unwell - these can be signs of blood problems
• bad headaches

Serious allergic reaction

In rare cases, it's possible to have a serious allergic reaction (anaphylaxis) to nitrofurantoin.

These are not all the side effects of nitrofurantoin. For a full list see the leaflet inside your medicines packet.

What to do about:

• feeling sick (nausea) - take nitrofurantoin with or after a meal or snack. It may also help if you avoid rich or spicy food.
• being sick (vomiting) and diarrhoea - drink lots of fluids, such as water or squash to avoid dehydration. Take small, frequent sips if you feel sick. Signs of dehydration include peeing less than usual or having strong-smelling pee. Do not take any other medicines to treat diarrhoea or vomiting without speaking to a pharmacist or doctor.
• loss of appetite - eat when you would usually expect to be hungry. If it helps, eat smaller meals more often than usual. Snack when you're hungry. Have nutritious snacks that are high in calories and protein, such as dried fruit and nuts.
• headaches - make sure you rest and drink plenty of fluids. Do not drink too much alcohol. Painkillers you can buy without a prescription, such as paracetamol and ibuprofen, are safe to take with nitrofurantoin. Speak to your doctor if these don't help with the headaches or the headaches are severe.
• dizziness or feeling sleepy - if nitrofurantoin makes you feel dizzy, stop what you're doing and sit or lie down until you feel better.

It's usually safe to take nitrofurantoin during pregnancy and while breastfeeding.

It's very unlikely that nitrofurantoin is harmful during pregnancy. It goes straight into your pee, so very little of the medicine passes through to the unborn baby. But do not take nitrofurantoin during labour and childbirth, as there's a chance that it can affect the baby's blood.

For more information about how nitrofurantoin can affect you and your baby during pregnancy, visit the Best Use of Medicines in Pregnancy (BUMPS) website.

Nitrofurantoin and breastfeeding

Tell your doctor before taking nitrofurantoin if you're breastfeeding. Although it's generally safe to take this medicine while breastfeeding, it may not be suitable for all breastfed babies.

Do not take nitrofurantoin while breastfeeding if your baby has a rare condition called glucose-6-phosphate dehydrogenase (G6PD) deficiency.

There are some medicines that don't mix well with nitrofurantoin.

Tell your doctor if you're taking these medicines before you start nitrofurantoin treatment:

• indigestion remedies known as antacids, particularly those that contain magnesium
• certain medicines for gout, including probenecid or sulfinpyrazone
• cystitis remedies you can buy from a pharmacy
• antibiotics known as quinolones, including nalidixic acid, ciprofloxacin, levofloxacin, norfloxacin, ofloxacin and moxifloxacin

Typhoid vaccine given by mouth may not work properly if you're taking nitrofurantoin. This doesn't apply to typhoid vaccines given by injection.

Mixing nitrofurantoin with herbal remedies and supplements

There are no known problems with taking herbal remedies and supplements with nitrofurantoin.