Nitrofurantoin 100mg MR Capsules

Nitrofurantoin is a prescription-only antibiotic used to treat uncomplicated urinary tract infections (UTIs) in women, including cystitis (bladder infection). It works by interfering with the bacteria's ability to produce the proteins, DNA, and cell walls they need to survive and multiply — effectively killing the bacteria responsible for the infection. Unlike some other antibiotics, nitrofurantoin concentrates specifically in the urinary tract and bladder, making it highly targeted and effective for UTIs while minimising its impact on the rest of the body. It is one of the most commonly prescribed UTI antibiotics in the UK and is available quickly and conveniently through Access Doctor following a short online consultation.

Nitrofurantoin gets to work in the bladder within hours of the first dose. Most women begin to notice a meaningful improvement in their symptoms — such as reduced burning, urgency, and frequency — within 24 to 48 hours of starting treatment. Full relief typically occurs over 3 to 5 days. It is essential to complete the full prescribed course even if you feel completely better before it is finished — stopping early can allow the infection to return and may contribute to antibiotic resistance. If your symptoms have not improved within 48 hours of starting treatment, or if they get worse at any point, speak to your GP for more advice.

Nitrofurantoin is available in two forms — a modified-release capsule (100mg) taken twice a day, or an immediate-release capsule (50mg to 100mg) taken four times a day. Access Doctor will only prescribe a 3-day course of 100mg modified release capsule to treat uncomplicated UTI symptoms. Always take nitrofurantoin with food or a glass of milk — this significantly improves absorption and helps to reduce the risk of stomach upset. Try to space your doses as evenly as possible throughout the day. Never take a double dose to make up for a missed one.

Yes — this is a very commonly asked question and completely normal. Nitrofurantoin can turn your urine dark yellow or brown during treatment. This is harmless, is caused by the medication itself, and is not a sign that anything is wrong. Your urine will return to its normal colour as soon as you finish the course. If your urine appears red or you notice blood in it, however, speak to your doctor as this may indicate a more serious infection or another underlying condition.

Most women complete a short course of nitrofurantoin without significant problems. The most commonly reported side effects include nausea, loss of appetite, stomach pain, diarrhoea, and headache — taking it with food helps to minimise these. Some women develop a mild skin rash or experience dizziness. In rare cases, nitrofurantoin can cause more serious lung reactions — including breathlessness, coughing, or a fever — particularly during long-term use. This is uncommon with short courses but if you notice any new or worsening breathing symptoms while taking nitrofurantoin, stop taking it and seek medical attention promptly. Very rarely, liver problems can occur — signs include yellowing of the skin or whites of the eyes, dark urine, or persistent nausea. If you notice any of these, contact your GP immediately.

Nitrofurantoin is not suitable for everyone. It should not be taken by people with significant kidney impairment — specifically those with an estimated glomerular filtration rate (eGFR) below 45 ml/min — as it will not work effectively and may build up to toxic levels. It is also not suitable for anyone with a known allergy to nitrofurantoin, a history of liver problems caused by nitrofurantoin, or a history of lung reactions associated with the medication. It should be used with caution in older adults, in whom kidney function is often reduced. Always provide your full medical history during your online assessment at Access Doctor so that our prescribers can make an accurate decision if the treatment is suitable for you or not.

There is no direct chemical interaction between nitrofurantoin and alcohol, but it is still sensible to keep alcohol to a minimum while taking it. Alcohol can worsen some side effects such as nausea and dizziness, can irritate the bladder and make UTI symptoms feel worse, and can slow your body's recovery. For the best results, try to avoid or significantly reduce alcohol intake for the duration of your antibiotic course and until your UTI has fully cleared.

Nitrofurantoin is one of the antibiotics most commonly prescribed for UTIs during pregnancy, particularly in the second trimester, as it is considered relatively safe during this period. However, it should be avoided in the first trimester if possible, and must not be taken in the last 2 to 4 weeks of pregnancy — as it can cause a serious blood condition in newborn babies called haemolytic anaemia. The prescribers at Access Doctor do not prescribe Nitrofurantoin if you have told us you are pregnant. We suggest that it is safer for you to obtain antibiotic treatment directly from your own GP if you are pregnant and have a UTI. It is important to seek treatment promptly as UTIs in pregnancy can progress to kidney infections quickly. Always tell your prescriber at Access Doctor if you are pregnant before starting any antibiotic. If you are breastfeeding, nitrofurantoin can be taken but should be used with caution — speak to your own GP or doctor who can advise on whether it is the most appropriate choice for you.