Nitrofurantoin for urine infections

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Take nitrofurantoin with (or just after) a meal or a snack. This will help your body to absorb the medicine and help to prevent stomach upset.

Space out your doses evenly throughout the day, and remember to finish the course unless you are told to stop.

Nitrofurantoin may darken the colour of your urine. This is nothing to worry about.

The most common side-effect is feeling sick.

Type of medicineAn antibacterial
Used forUrinary tract infection (UTI) in adults and children
Also calledFuradantin®; Macrobid®; Macrodantin®
Available asTablets, capsules, and prolonged-release capsules

A urine infection is often called a urinary tract infection (UTI) by doctors. Most urine infections are caused by bacteria that come from your own bowel. They are usually easily treated with a short course of an antibacterial medicine such as nitrofurantoin. Occasionally, longer-term treatment is needed to prevent infections from coming back. Nitrofurantoin works by killing the bacteria causing the infection.

Some medicines are not suitable for people with certain conditions, and sometimes a medicine may only be used if extra care is taken. For these reasons, before you start taking nitrofurantoin it is important that your doctor or pharmacist knows:

  • If you are pregnant, trying for a baby or breast-feeding.
  • If you have liver or kidney problems.
  • If you have diabetes
  • If you have been told you are anaemic, or have low levels of vitamin B or folic acid.
  • If you have breathing problems.
  • If you have a problem called peripheral neuropathy. This is where your nerves cause pain or numbness.
  • If you have been told you have porphyria or glucose 6-phosphate dehydrogenase (G6PD) deficiency. These are rare inherited disorders.
  • If you are taking any other medicines. This includes any medicines you are taking which are available to buy without a prescription, such as herbal and complementary medicines.
  • If you have ever had an allergic reaction to a medicine.
  • Before you start this treatment, read the manufacturer's printed information leaflet from inside your pack. The leaflet will give you more information about the specific brand of nitrofurantoin you have been given, and a full list of side-effects which you may experience from taking it.
  • Take nitrofurantoin tablets/capsules exactly as your doctor tells you to - your dose will be on the label of your pack to remind you. Your dose will depend upon which brand you are taking, and whether you are being treated because you have an infection, or to prevent an infection. As a guide, if you are taking tablets or Macrodantin® capsules to treat an infection, it is likely that you will be prescribed one tablet/capsule to take four times daily for 3-7 days. If you have been given nitrofurantoin to give to your child, follow the dosing directions on the label of the pack carefully, as the dose prescribed will depend upon how much your child weighs. If you have been given Macrobid® capsules, you will be asked to take one capsule twice daily, as these capsules release nitrofurantoin more slowly and so work for longer.
  • Take each of your doses with a snack or after eating a meal. Space them out evenly throughout the day - this means tablets/capsules prescribed four times daily should be taken every six hours, and those prescribed twice daily should be taken every 12 hours.
  • Keep taking the tablets/capsules until the course is finished unless you are told to stop. It is important you do this even if you feel well, otherwise your infection may come back.
  • If you forget to take a dose, take it as soon as you remember. If it is almost time to take your next dose when you remember, skip the missed dose and take your next dose when it is due. Do not take two doses together to make up for a forgotten dose.
  • Most people improve within a few days of starting treatment. If your symptoms do not improve despite taking nitrofurantoin, go back to see your doctor, as you may need an alternative antibiotic. This is because some bacteria are resistant to some types of antibiotics.
  • Nitrofurantoin may colour your urine yellow/brown. This is harmless.
  • If you buy any medicines, check with a pharmacist that they are suitable to take with nitrofurantoin. Some antacids can interfere with nitrofurantoin and stop it from working properly.
  • If you have diabetes, this medicine might interfere with some urine tests for glucose. Ask your doctor or pharmacist for advice if you normally monitor your glucose levels with urine tests.
  • If you are using oral combined hormonal contraception (the 'pill'), the current recommendation is that additional contraceptive precautions such as condoms are not required during a course of this antibiotic, unless you are sick or have diarrhoea. If you need further advice about this, speak with your doctor or pharmacist.
  • If you are having an operation or dental treatment, tell the person carrying out the treatment that you are taking nitrofurantoin. This is because it can affect the results of some medical tests.
  • This medicine may stop the oral typhoid vaccine from working. If you are having any vaccinations, make sure the person treating you knows that you are taking it.

Along with their useful effects, most medicines can cause unwanted side-effects although not everyone experiences them. These usually improve as your body adjusts to the new medicine, but speak with your doctor or pharmacist if any of the following side-effects continue or become troublesome.

Common nitrofurantoin side-effects - these affect less than 1 in 10 people who take this medicineWhat can I do if I experience this?
Feeling or being sick, loss of appetiteStick to simple foods - avoid rich or spicy meals. Remember to take nitrofurantoin after food
DiarrhoeaDrink plenty of water to replace lost fluids
Feeling dizzy or sleepyIf this happens, do not drive or use tools or machines

Important: your doctor will have discussed with you the possibility of a less common side-effect that may affect your lungs. You should let your doctor know straightaway if you experience any of the following:

  • Any difficulty breathing, pains in your chest, coughing, chills, or a high temperature.

If you experience any other symptoms which you think may be due to this medicine, speak with your doctor or pharmacist.

  • Keep all medicines out of the reach and sight of children.
  • Store in a cool, dry place, away from direct heat and light.

Never take more than the prescribed dose. If you suspect that you or someone else might have taken an overdose of this medicine, go to the accident and emergency department of your local hospital at once. Take the container with you, even if it is empty.

This medicine is for you. Never give it to other people even if their condition appears to be the same as yours.

Do not keep out-of-date or unwanted medicines. Take them to your local pharmacy which will dispose of them for you.

If you have any questions about this medicine ask your pharmacist.

Further reading & references

  • British National Formulary; 64th Edition (Sep 2012) British Medical Association and Royal Pharmaceutical Society of Great Britain, London
  • Manufacturer's PIL; Furadantin® 50 mg and 100 mg Tablets, Mercury Pharma Group, The electronic Medicines Compendium. Dated April 2011.
  • Manufacturer's PIL; Macrobid® Capsules 100 mg, Mercury Pharma Group, The electronic Medicines Compendium. Dated April 2011.

Disclaimer: This article is for information only and should not be used for the diagnosis or treatment of medical conditions. EMIS has used all reasonable care in compiling the information but make no warranty as to its accuracy. Consult a doctor or other health care professional for diagnosis and treatment of medical conditions. For details see our conditions.

Original Author:
Helen Allen
Current Version:
Peer Reviewer:
Dr Helen Huins
Document ID:
3289 (v25)
Last Checked:
Next Review:
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