Trimethoprim Tablets for UTI & Respiratory Infections: Complete Guide
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Order Trimethoprim →What Is Trimethoprim?
Trimethoprim is a prescription antibiotic belonging to the dihydrofolate reductase inhibitor class. It is used to treat a range of bacterial infections — primarily urinary tract infections (UTIs) including cystitis — and is available as 200mg tablets from Access Doctor following a GPhC-regulated online consultation.
What Infections Does Trimethoprim Treat?
Urinary Tract Infections
Trimethoprim is primarily used for acute urinary tract infections (UTIs), including:
- Cystitis — bladder infection causing frequent urination, urgency, and burning
- Urethritis — inflammation of the urethra
- Kidney infection (pyelonephritis) — more serious infection causing back pain, fever, and nausea
- Recurrent UTIs — trimethoprim may be used for longer-term prevention
For uncomplicated UTIs, NICE recommends nitrofurantoin as the first-choice antibiotic, with trimethoprim as the recommended alternative. See our full comparison of UTI antibiotics.
Respiratory Tract Infections
Trimethoprim can also be used for certain respiratory tract infections, typically in combination with other antibiotics. Acute respiratory infections — including bronchitis and pneumonia — may respond to trimethoprim-based regimens, though this is less common than its use for UTIs.
Trimethoprim is not effective against viral infections — including the common cold, flu, or COVID-19. Always use antibiotics only when prescribed for a confirmed or strongly suspected bacterial infection.
How Does Trimethoprim Work?
Trimethoprim is a dihydrofolate reductase inhibitor. It works by disrupting the bacteria’s ability to produce folic acid — a vital nutrient they require to grow and survive. By blocking this enzyme pathway, trimethoprim effectively stops the bacteria from multiplying, allowing the body’s immune system to clear the infection.
How to Take Trimethoprim
| Aspect | Guidance |
|---|---|
| Standard adult dose (UTI) | 200mg twice daily — morning and evening |
| Duration | 7 days for most UTI courses (may vary by clinical context) |
| Administration | Swallow tablets whole with a glass of water. Can be taken with or without food. |
| Timing | Same time(s) each day to maintain consistent blood levels |
| Course completion | Always finish the full course — even if symptoms resolve early |
| Missed dose | Take as soon as you remember, unless almost time for next dose. Never double up. |
Important Precautions
Before taking trimethoprim, inform your prescriber if you have any of the following:
- Kidney problems: Trimethoprim can affect potassium levels — risky with significant kidney impairment
- Folic acid deficiency: Trimethoprim interferes with folate absorption — monitor if pre-existing deficiency
- Diabetes: Some diabetes medications can interact with trimethoprim
- Pregnancy / breastfeeding: Avoid in first trimester due to folate interference — discuss with your prescriber
- Blood disorders / porphyria: May not be suitable
Side Effects of Trimethoprim
Trimethoprim is generally well tolerated. Common side effects include nausea and vomiting, diarrhoea, headache, and skin rash. These are usually mild and resolve after completing the course.
Seek immediate medical attention if you experience: severe allergic reaction (hives, difficulty breathing, swelling of face/throat); easy bruising or bleeding; high fever with sore throat and mouth sores; muscle weakness or irregular heartbeat. See our full guide: Trimethoprim side effects: your questions answered.
Getting Trimethoprim from Access Doctor
Trimethoprim is a prescription-only medication. Access Doctor offers a streamlined, confidential online consultation with GPhC-registered pharmacist independent prescribers who assess your symptoms and medical history. Once approved, trimethoprim is discreetly packaged and dispatched — with delivery options through Royal Mail to suit your needs.
💊 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 →Order Trimethoprim Online
Our GPhC-registered pharmacist independent prescribers will review your consultation and prescribe the most appropriate UTI antibiotic. Next-day delivery available.
Treat Cystitis Online →Frequently Asked Questions About Trimethoprim
What infections does trimethoprim treat?
Trimethoprim is primarily used for UTIs including cystitis, kidney infections, and urethritis. It can also be used for certain respiratory infections, ear infections, and acne, though this is less common.
How does trimethoprim work?
Trimethoprim is a dihydrofolate reductase inhibitor. It blocks bacteria’s ability to produce folic acid — a nutrient essential for their growth. This stops bacteria multiplying and allows the immune system to clear the infection.
How do I take trimethoprim tablets?
The standard UTI dose is 200mg twice daily. Swallow whole with water. Complete the full 7-day course even if symptoms resolve early. Take doses at the same time each day.
Can I drink alcohol while taking trimethoprim?
Yes, in moderation. Excessive alcohol can weaken the immune system and potentially prolong infection. It is advisable to keep alcohol to a minimum during any antibiotic course.
What if I miss a trimethoprim dose?
Take it as soon as you remember, unless your next dose is imminent. Skip the missed dose in that case and continue your regular schedule. Never double up.
Is trimethoprim safe in pregnancy?
Trimethoprim should generally be avoided in the first trimester as it can interfere with folate metabolism. It may be used in the second and third trimesters when clinically necessary. Always inform your prescriber if you are pregnant or breastfeeding.
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.