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Trimethoprim is an antibiotic medicine indicated for the treatment of bacterial infections, including cystitis. It is available as a generic tablet via our online clinic service.

To buy Trimethoprim online from our pharmacy, you’ll need to take our UTI questionnaire so our prescriber can make sure it’s right for you. Approved orders are shipped by next-day courier.


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PLEASE NOTE: This treatment is not available through our online pharmacy service. This page is for information only. If you are experiencing any of the symptoms related to the condition(s) this medication treats, we strongly recommend that you see your GP in person.

This content was reviewed by a clinician on

26 April 2022
dr daniel

Dr Daniel Atkinson

(GP Clinical Lead - GMC No. 4624794) 26 April 2022
Product information

Trimethoprim is an antibiotic medicine. It is used in the treatment of various bacterial infections, including cystitis. The medication has been noted for its fast mechanism of response, and its ability to reduce symptoms quickly. This item is sold as a generic tablet, but the same medication has previously been made by GlaxoSmithKline under the names Proloprim and Triprim.

It is thought that most women will encounter cystitis at some point in their lives. Men do encounter it, but it’s much less common. The condition can be brought on by the presence of certain bacteria in the urinary tract, and can cause inflammation and feelings of pain in the bladder, as well as urinary discomfort. Some may notice that their urine becomes dark or discoloured too.

There are a number of reasons why someone might develop cystitis; but many of them involve the transfer of bacteria from other parts of the body, or from foreign objects, to the vagina (or penis). Bathroom habits (such as wiping from the anus to the vagina) can induce infection, as can sex, or the use of tampons or vaginally-inserted contraceptive devices.

Milder cases of cystitis may clear up without the need for treatment. In some instances, the body’s immune system is able to tackle the infection and stop it from developing. However, persistent or severe incidences of the illness will usually necessitate a course of medication.

For most bacterial infections, antibiotics are the recommended treatment. This is because they eliminate the illness by combating the bacteria responsible. 

Trimethoprim is prescribed when the first-line treatments for cystitis, MacroBID and Nitrofurantoin, aren’t suitable (for example, if they’ve been used previously and haven’t worked, or if someone is allergic to them). If you haven’t consulted with a doctor about those first, you should do so before taking Trimethoprim.

Trimethoprim works by stopping the growth of the offending bacteria. It does this by inhibiting the capacity of bacterial cells to duplicate themselves through the production of DNA material. Once the bacteria is no longer able to spread, the immune system takes over and destroys what remains of the infection.

Please note that men ordering this treatment from us will also receive a test pot in their parcel. A urine sample must be provided in this pot before treatment is started, and taken to a GP or sexual health clinic to be analysed.

Take our UTI questionnaire to have your case reviewed by one of our prescribers. They will give you the option to buy Trimethoprim online once your prescription has been approved. All orders are shipped by next-day delivery from our UK pharmacy.

Page last reviewed:  26/04/2022


It is essential when using any medication to read the instructions provided first. Adhering to the guidelines set out in these, and following the directions supplied by your doctor, will help you to minimise the risk of side effects, and ensure the medicine is effective. 

  1. If you are male, you will need to provide a sample of your urine using the provided pot, and send the sample to your GP or a GUM clinic for testing, prior to starting your course of Trimethoprim
  2. Take as directed by your prescriber.
  3. For cystitis infections in women, this is one 200mg tablet twice daily for three days.
  4. For cystitis infections in men, this is one 200mg tablet twice daily for seven days.
  5. Swallow tablets whole with water.
  6. Never exceed the prescribed amount.
  7. If you miss a dose, contact your doctor as soon as possible for advice on what to do next.

These directions are only intended as a guide. Please refer to the patient information leaflet for more detailed instructions.

Download Trimethoprim PDF

Download Trimethoprim Oral Suspension PDF

Page last reviewed:  26/04/2022
Please read the patient information leaflet for this medicine fully before use:

Trimethoprim For men (200mg)

Trimethoprim For women (200mg)

Side effects & Warnings

Side effects

Even though only a minority of people may experience them, you should always be aware of the potential side effects a medicine may cause. This is so that you can act fast and get the medical help you need if you notice the appearance of anything unusual. Side effects associated with this medicine include:

Common (frequency unknown):

Diarrhoea, nausea and vomiting, headache, rash, anaemia, thrush, sore throat, mouth ulcers.

Very rare (1 in 10000 people or less):

Feelings of agitation, allergic reactions, cough, redness of the eyes, low blood sugar, photosensitivity, kidney problems, constipation, jaundice, dizziness, tiredness, convulsions, sore tongue.

Contact your doctor if you notice any of the above. This is not a complete list of side effects. For a more detailed account, refer to the leaflet provided with the product.

Taking it with other medicines

Antibiotics can react with other medicines and affect their efficacy. Inform your prescriber during consultation of any other medications you are using. Never use more than one product or medication for cystitis unless your doctor tells you to.

If you are taking any of the following treatments, you may be unable to use Trimethoprim, or only be able to use it under careful medical supervision: repaglinide, procainamide, digoxin, diuretics, rifampicin, anticoagulants, phenytoin, pyrimethamine, dapsone, or immunosuppressant drugs.

Conditions to look out for

Disclose your medical history to your prescriber before use. Kidney problems, folic acid deficiency, high potassium levels, or porphyria, are examples of conditions that may affect your suitability to the medicine.

Pregnancy and breastfeeding

Trimethoprim must not be used during pregnancy.

If you are planning on becoming pregnant or are breastfeeding, speak to your doctor before using this drug.

Driving using machinery

Your driving and capacity to use machines is not likely to be affected by this medication.

Page last reviewed:  26/04/2022
Please read the patient information leaflet for this medicine fully before use:

Trimethoprim For men (200mg)

Trimethoprim For women (200mg)


Can I still drink alcohol?

Alcohol is not known to affect the performance of this product. However, it can inhibit the function of some antibiotics, so we would recommend that you do not drink alcohol while using this medication.

Will I still be able to drive?

This medication should not have any effect on your capacity to drive. But if you experience any side effects which could impair your judgement or coordination, you should not drive and seek medical advice right away.

Can I take the medicine while pregnant?

No. This product is not suitable for use by those who are pregnant or breastfeeding.

How should I store it?

Always in a dry environment at room temperature, away from direct sunlight.

Am I allergic to anything in the medicine?

The tablets contain trimethoprim, lactose monohydrate, povidone K30, crospovidone, sodium starch glycolate Type A and magnesium stearate.

Trimethoprim Oral Suspension fluid contains trimethoprim, xanthan gum(E415), maltitol
liquid (E965), polysorbate 80, microcrystalline cellulose (E460), saccharin sodium(E954), citric acid monohydrate, sodium carboxymethylcellulose(E466), sodium methyl parahydroxybenzoate(E219), sodium propyl parahydroxybenzoate(E217), aniseed flavour and purified water.

Do not use either of the above if you are allergic to any containing ingredients.

Is it available over-the-counter?

No. You can only buy Trimethoprim with a prescription. This is because a doctor will need to assess the suitability of this medicine before issuing it to you.

Can I buy Trimethoprim online?

Yes, if our prescribers determine it is suitable for you. Fill in our short form and a GMC registered doctor will review your answers. We ship all approved orders by tracked, next-day courier.

Page last reviewed:  26/04/2022
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