What are Trimethoprim Tablets?
Trimethoprim tablets are an oral medication used to treat urinary tract infections. Trimethoprim is a type of antibiotic that works by stopping the growth of bacteria in the urinary tract. This medication is typically taken twice a day for a period of 3 to 7 days, and should be taken with plenty of water to help flush the bacteria from the urinary tract. Some possible side effects of Trimethoprim tablets include upset stomach, diarrhea, and dizziness.
In the UK, Trimethoprim tablets are classified as a prescription-only medication, meaning that they can only be obtained with a prescription.
UTIs can affect both men and women, we currently only offer treatment for women, as men usually need a longer course to completely rid themselves of infection and can be the sign of something more serious. If you are a man and require treatment visit your doctor or a clinic that specializes in sexual health.
Trimethoprim is one first-choice option for a lower UTI when the risk of bacterial resistance is low. Your prescriber will consider previous antibiotic use and any urine test results when choosing treatment.
As with any antibiotic it is important you complete the course even if you start to feel better. Failing to complete the course can lead to reinfection and antibiotic resistance.
How to buy Trimethoprim Tablets online
You can use our online prescription service to buy Trimethoprim online in the UK with free and next day delivery. We are a regulated GPhC registered pharmacy based in the UK. Any website that claims to sell Trimethoprim without a prescription is operating illegally and you could be purchasing counterfeit / fake medicine.
Upon completion of your order, our independent prescriber will then review your online assessment. If your assessment is approved, our pharmacy team will then receive a prescription and dispense your order, which will be dispatched the same day using your chosen delivery method.
How it works
Trimethoprim is absorbed into the bloodstream and then transported to the urinary tract, where it can exert its antimicrobial effects. It is an antibiotic it kills bacteria by stopping them making a substance called folic acid, which they need to survive, this makes it difficult for the bacteria to multiply and spread, allowing the body's immune system to fight off the infection more effectively.
How to take Trimethoprim Tablets
The usual adult dose of trimethoprim for a UTI is 200mg twice daily. The course length depends on the patient and infection; follow your prescription label and complete the prescribed course even if you feel better.
Contact your doctor if symptoms worsen at any time or have not started to improve after two days. You may need reassessment or a different antibiotic; do not extend the course yourself. Use trimethoprim only for the infection it was prescribed for.
How do I know if I have a UTI?
UTIs are common in both men and women. Common symptoms include:
- Dysuria (pain when urinating)
- Nocturia (needing to urinating more at night)
- Dark or cloudy urine with a strong smell
- Blood in your urine
- Needing to urinate more often
- Lower abdomen pain
- A high temperature
- A low temperature below 36C
UTIs are usually easily treated however if they are left untreated they can become more serious.
UTI symptom relief
Some ways to help relieve the symptoms of a urinary tract infection (UTI) include:
- Drink plenty of fluids to help flush out bacteria from the urinary tract
- Don't fight the urge to urinate (pee), go to the toilet if you get the urge to urinate
- Take over the counter medicines such as paracetamol and ibuprofen
- Apply a heat pad or warm compress to your lower belly to help relax the muscles in the urinary tract
- Drink cranberry juicy or cystitis sachets
If you think you have a UTI these will only help relieve the symptoms and will not treat the cause.
How quickly does Trimethoprim work?
You should begin to feel better within a day or two. Contact your doctor if symptoms have not started to improve after two days or get worse at any time, even if you still have tablets left. Do not wait until the end of a three- or seven-day course to seek advice. Get urgent medical advice for fever or shivering, pain in your side or back under the ribs, vomiting or feeling very unwell.
Should I take Macrobid or Trimethoprim?
NICE guidelines first line choice for treating a UTI is Nitrofurantoin, as there is a lesser chance of antibiotic resistance with Macrobid than Trimethoprim.
Trimethoprim is still a good choice and will produce good results in most women with some finding better results using it. Trimethoprim is also a good alternative for those with certain medical conditions such as kidney problems or if your urine sample has been tested and shows the bacteria is not antibiotic resistant.
What else can I take?
Painkillers are commonly taken alongside Trimethoprim such as Aspirin, Paracetamol or Ibuprofen.
Cystitis sachets or cranberry juice can help provide some symptom relief.
Trimethoprim and pregnancy
Tell your prescriber if you are pregnant or trying to conceive. Trimethoprim is not usually recommended in early pregnancy because it can lower folate levels. A doctor may still prescribe it when needed; they will weigh the options and may prescribe high-dose folic acid. Do not assume it is automatically suitable after the first 12 weeks.
Trimethoprim and breastfeeding
If your baby is healthy it is ok to take Trimethoprim while breastfeeding. A small amount will pass through breast milk. It is unlikely the tiny amount of Trimethoprim your baby receives from your milk will do them any harm. It is unlikely to have any affect, but if you notice any change in you babys behaviour such as not feeding as well as usual, is unusually sleepy or you have any concerns contact your doctor or health visitor.
Trimethoprim side effects
Trimethoprim can cause itching or a skin rash, nausea, vomiting or diarrhoea. Do not assume that dark-brown urine is a harmless effect of this medicine: it can be a sign of blood in the urine and needs urgent medical advice. Other possible side effects include:
- Nausea (feeling sick)
- Vomiting (being sick)
- Diarrhoea
- Loss of appetite
- Headaches
- Dizziness
For a full list of side effects refer to either the SPC or the patient information leaflet.
If you experience any more serious side effects such as a cough or high temperature, signs of jaundice such as yellowing of skin or the whites of the eyes, unexplained bruising or bleeding, call either your doctor or 111. If you experience signs of an allergic reaction, chest pains or pins & needles call 999.
Trimethoprim alternatives
An alternative to Trimethoprim is Macrobid.Macrobid is usually the first line for UTIs as there is less resistance to it. Trimethoprim is still used in some women and some women will find it works better then Macrobid.
Frequently asked questions
What are the possible side effects of Trimethoprim?
Some possible side effects of Trimethoprim include: nausea, vomiting, diarrhoea, loss of appetite, headache, dizziness, rash. More serious side effects include: Yellowing of the skin or whites of the eyes (jaundice), unusual bruising or bleeding, confusion or hallucinations, chest pain or difficulty breathing. If these side effects occur contact your doctor immediately.
How should I take Trimethoprim?
Trimethoprim tablets are usually taken twice a day with food and a glass of water. Taking it with food helps to prevent side effects and the water will help the antibiotic work.
Can I drink alcohol while taking Trimethoprim?
Yes you can drink alcohol while taking Trimethoprim.
Can I buy Trimethoprim tablets over the counter?
No they must be prescribed.
Can I take Trimethoprim if I'm pregnant or breastfeeding?
Ask your prescriber before using trimethoprim during pregnancy, particularly in the first 12 weeks. If your baby is healthy, trimethoprim can usually be taken while breastfeeding, but tell your doctor if the baby is premature, unwell or has jaundice. Contact your health visitor or doctor if feeding or behaviour changes.
What should I do if I miss a dose of Trimethoprim?
If you have missed a dose take it as soon as you remember unless it is time to take your next dose. If it is time for your next dose skip the missed dose.
Is it safe to buy Trimethoprim tablets from your pharmacy?
We are a General Pharmaceutical Council (GPhC) registered pharmacy and we source all our pharmaceutical products from reputable wholesalers, the same wholesalers that provide the medicines used to fill NHS prescriptions.
If you buy them from an unregistered pharmacy you may be wasting your money at best or at worse harm yourself buying and taking fake tablets. Always check to make sure where you are buying them from are registered with the GPhC.Do Trimethoprim tablets expire?
Yes, like most medicines it has a shelf life and will become less effective if it is left unused. Always check the expiry date of any medicines you are taking before you take them, the expiry date refers the end of the month. If you find your medication has expired, you can post them to us, bring them to us or take them to your nearest pharmacy for safe disposal.
How should I store Trimethoprim tablets?
They should be stored in a dry area below 30°C and kept out of direct sunlight. Storing the tablets incorrectly could result in the tablets becoming less effective.
Sources and further information
- NHS: about trimethoprim (checked 8 September 2026)
- NHS: trimethoprim side effects (checked 8 September 2026)
- NICE NG109: lower urinary tract infection antimicrobial prescribing (checked 8 September 2026)
- Summary of Product Characteristics (SPC)
- Further product information
- NHS: trimethoprim during pregnancy and breastfeeding (accessed 8 September 2026)
