UTI Treatments: Nitrofurantoin vs Trimethoprim
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Treat Cystitis Online →Overview
If you have ever had a burning sensation when urinating, a constant urgency to go, or cramping in the lower abdomen — you will have shared the discomfort experienced by millions of UK women who develop a urinary tract infection (UTI) each year. The cause of UTIs is almost always bacterial, and the most effective treatment is a short course of antibiotics.
The two most commonly prescribed antibiotics for UTIs in the UK are nitrofurantoin and trimethoprim. This guide compares them — how they work, who they are suitable for, and which NICE recommends as first choice.
UTIs are more common in women than men for anatomical reasons — the female urethra is shorter and positioned closer to the anus, making bacterial transfer easier. Hormonal changes, sexual activity, and certain contraceptive methods also increase risk.
Nitrofurantoin (Macrobid / Macrodantin)
Nitrofurantoin is the current first-line antibiotic recommended by NICE for uncomplicated UTIs and cystitis in the UK. It works by interfering with bacterial energy metabolism and DNA synthesis, killing the bacteria causing the infection.
A key feature of nitrofurantoin is that it is rapidly absorbed from the bloodstream and concentrated in the urine — meaning it reaches very high levels at the exact site of a urinary tract infection, making it highly effective for this specific purpose. This also means it is not effective for infections elsewhere in the body.
- First-line NICE recommendation for uncomplicated UTIs (if kidney function is adequate)
- Concentrated in urine — high efficacy at the site of bladder infection
- Take with or immediately after food to reduce stomach upset
- May turn urine dark yellow or brown — this is normal and temporary
- Also known by brand names Macrobid and Macrodantin
- Generally suitable during pregnancy and breastfeeding (with some caution near term)
Who should not take nitrofurantoin?
- Those with an allergy to nitrofurantoin
- Those with severe kidney disease or poor kidney function (eGFR <45 ml/min)
- Those with porphyria or G6PD deficiency (rare inherited conditions)
- Those with diabetes-related kidney complications
- Those with anaemia or vitamin B deficiency
Trimethoprim
Trimethoprim is an antibiotic used to treat UTIs including cystitis, and occasionally for chest infections and acne. It is taken twice daily and works by blocking the production of folate — a nutrient bacteria require to grow and multiply.
Trimethoprim was once the first-line treatment for UTIs, but increased antibiotic resistance has reduced its effectiveness in some areas. NICE now recommends it as an alternative to nitrofurantoin — suitable where resistance rates are low and nitrofurantoin is not appropriate. In the vast majority of cases (approximately 90%), trimethoprim remains an effective choice for UTIs.
- Second-line NICE recommendation (or first-line where nitrofurantoin is not suitable)
- Can treat some infections beyond the urinary tract (chest, skin, acne)
- Usually taken twice daily
- Children and adults can take trimethoprim
- Does not contain penicillin — safe for those with penicillin allergy
Who should not take trimethoprim?
- Those with an allergy to trimethoprim
- Those with liver or kidney problems
- Those with anaemia or low folic acid levels
- Those with porphyria or blood disorders
- Pregnant women — avoid in first trimester (interferes with folate)
Nitrofurantoin vs Trimethoprim: Head-to-Head
| Feature | 💊 Nitrofurantoin | 💊 Trimethoprim |
|---|---|---|
| NICE guidance | First choice | Alternative / second line |
| How it works | Disrupts bacterial energy metabolism & DNA synthesis | Blocks bacterial folate production |
| Effective for | UTIs only (concentrated in urine) | UTIs + some other infections |
| Typical dose | 100mg modified-release twice daily, 5 days (or 50mg 4x daily) | 200mg twice daily, 7 days |
| Penicillin-free | Yes | Yes |
| Pregnancy | Generally suitable (caution near term) | Avoid in first trimester |
| Most common side effect | Stomach upset (take with food) | Mild skin rash or itching |
| Urine discolouration | May turn urine dark yellow/brown (normal) | No |
| Resistance trend | Lower resistance currently | Increasing resistance in some areas |
NICE Guidelines on UTI Antibiotics
NICE recommends nitrofurantoin as first-choice for uncomplicated lower UTIs in women, provided eGFR is ≥45 ml/min. Trimethoprim is recommended as an alternative where nitrofurantoin is not appropriate, and where the risk of resistance in the local area is considered low. Both antibiotics are taken for 3–7 days depending on formulation and clinical context.
Completing your course matters: Always finish the full prescribed course of antibiotics — even if symptoms improve within a day or two. Stopping early risks the infection returning and contributes to antibiotic resistance, making future treatment harder.
How Access Doctor Prescribes UTI Antibiotics
Access Doctor follows national NICE guidelines in all UTI prescribing. We recommend nitrofurantoin as first choice for women with confirmed uncomplicated cystitis. If trimethoprim is deemed more appropriate — based on your medical history, kidney function, pregnancy status, or local resistance patterns — our GPhC-registered pharmacist independent prescribers will recommend switching.
We only treat women with typical symptoms of acute uncomplicated cystitis. Where there is concern the infection has extended beyond the bladder (complicated UTI), we refer urgently to a GP. Read our guide: UTI or Not UTI? — When to seek urgent care.
💊 NICE First-Line Antibiotic
Nitrofurantoin (Macrobid)
MHRA-approved first-line antibiotic for cystitis & UTIs. Prescription via GPhC-regulated online consultation.
Order Nitrofurantoin →💊 Prescription Antibiotic
Trimethoprim
MHRA-approved alternative antibiotic for cystitis. Suitable where nitrofurantoin is not appropriate.
Order Trimethoprim →Get UTI Treatment — NICE-Guideline Prescribing
Our GPhC-registered pharmacist independent prescribers assess your consultation and prescribe the most appropriate antibiotic. Nitrofurantoin or trimethoprim — next-day delivery.
Treat Cystitis Online →Frequently Asked Questions
What is the best antibiotic for a UTI in the UK?
NICE recommends nitrofurantoin as first choice for uncomplicated UTIs in the UK (if kidney function is adequate). Trimethoprim is the recommended alternative. Access Doctor follows national guidelines in all UTI prescribing decisions.
What is nitrofurantoin used for?
Nitrofurantoin is an antibiotic specifically for urinary tract infections. It concentrates in the urine — making it highly effective at the site of infection. It is NICE first-line for uncomplicated cystitis in women. Also known as Macrobid or Macrodantin.
What is trimethoprim used for?
Trimethoprim is an antibiotic for UTIs and can also be used for some chest infections and acne. It is taken twice daily and is NICE second-line for UTIs — recommended as an alternative to nitrofurantoin where appropriate.
Can I take nitrofurantoin and trimethoprim together?
It is unlikely both would be prescribed simultaneously. Nitrofurantoin is typically given first; if the infection is resistant, trimethoprim or a stronger antibiotic is prescribed. Never take both unless specifically directed by your prescriber.
What are the side effects of nitrofurantoin?
The most common side effect is stomach upset — always take nitrofurantoin with food. It may turn urine dark yellow or brown, which is normal and temporary. Serious side effects are rare but can include pulmonary reactions with long-term use.
Is nitrofurantoin safe in pregnancy?
Nitrofurantoin is generally considered suitable during pregnancy, with some caution near term. Trimethoprim should be avoided in the first trimester as it can interfere with folate metabolism. Always inform your prescriber if you are pregnant or may become pregnant.
References
- NICE. Urinary tract infection (lower) — women. Clinical Knowledge Summaries. Available at: cks.nice.org.uk/topics/urinary-tract-infection-lower-women
- NHS. Cystitis. Available at: nhs.uk/conditions/cystitis
- UKHSA. English surveillance programme for antimicrobial utilisation and resistance (ESPAUR). Available at: gov.uk
- Electronic Medicines Compendium. Nitrofurantoin 100mg m/r capsules — SmPC. Available at: medicines.org.uk/emc
- Electronic Medicines Compendium. Trimethoprim 200mg tablets — SmPC. Available at: medicines.org.uk/emc
Medical disclaimer: This article is for informational purposes only and does not constitute medical advice. Always consult a qualified healthcare professional for diagnosis and treatment. Nitrofurantoin and trimethoprim are prescription-only medicines — a medical consultation is required before they can be dispensed. If you have a fever, loin/back pain, or are pregnant, seek urgent in-person medical care. In an emergency, call 999.