We are currently unable to process any orders



Trimethoprim is an effective medication for both killing bacteria commonly associated with cystitis and other urinary tract infections (UTIs).

Taking Trimethoprim twice a day over a three day period can provide fast and effective relief from the symptoms of cystitis in women.

This product is currently unavailable
Clock Icon

Order in the next to receive your order on the following days:

Type Delivery date Cost
DPD Next Day Tue 16 Aug - Wed 17 Aug £5.00
Royal Mail Tracked 48 Tue 16 Aug - Fri 19 Aug £3.00
Royal Mail Special Delivery™ Mon 15 Aug £5.95

What is Trimethoprim?

Trimethoprim is an effective antibiotic treatment used for a variety of bacterial infections. Trimethoprim is available in 100mg and 200mg dosages and works to stop the growth of bacteria in the body, allowing your body to fight against the infection.

Although Trimethoprim is a multipurpose medication, it is particularly adept at treating urinary tract infections.

Why Trimethoprim?

Trimethoprim is an effective way to clear uncomplicated cystitis infections. This prescription medication is capable of fighting the bacteria behind the infection and easing the symptoms within 24 hours. In most cases, the problem can be completely resolved within three days.

Trimethoprim tablets start to work within just a few hours, helping to eliminate symptoms fast. The medication has been clinically trialled and proven in its effectiveness too, as studies have shown it to be successful in treating UTIs.

Trimethoprim is also known to be highly effective and well tolerated. This means you experience a reduced risk of side effects.

Due to the growing resistance of bacteria to antibiotics, some patients may find that trimethoprim has reduced effectiveness against certain strains of bacteria.

How to take trimethoprim

Trimethoprim should be taken as soon as you recognise the symptoms and have been diagnosed with cystitis. The sooner you begin your course of cystitis medication, the less severe your infection is likely to be.

Trimethoprim capsules can be taken for both acute and long-term infections. They should be swallowed whole, and can be taken with or without food.

Take one tablet twice a day for three days. Aim to take the tablets at the same time each day. As it is an antibiotic treatment, you should complete your entire course of cystitis medication even if your symptoms seem to have disappeared beforehand.

What if you forget to take a tablet?

You should aim to complete your medication fully within the three-day period, but missing a dosage is nothing to worry about. If this does happen, simply take a dose when you remember or skip that dosage if you are close to the time when you should be taking your next tablet. Never take two tablets together to compensate for a missed dosage.

Side Effects

As with most prescription medication, there is a risk of side effects when you take Trimethoprim. These side effects are usually temporary and mild to moderate. Side effects may include:

  • Sore throat
  • Skin rashes
  • Loss of appetite
  • Diarrhoea
  • Anaemia

On very rare occasions, women who take Trimethoprim may experience the following side effects:

  • Mouth ulcers
  • Jaundice
  • Vertigo
  • Confusion

If you experience any of these side effects after you have completed your antibiotic medication, seek advice from your GP.


If you are taking any other medication, consult your pharmacist or GP before starting a course of antibiotics. Medications such as Digoxin, Ciclosporin, Repaglinide and diuretics should not be taken alongside Trimethoprim.

If you are pregnant, breastfeeding or allergic to any of the active ingredients contained within the medication, consult your GP before choosing the treatment.

You should also be wary if you have a folate deficiency, have impaired hepatic function or suffer from kidney or liver disease.


How does Trimethoprim work?

An imbalance of the natural bacteria in our body often leads to a bacterial infection, and when this occurs around the urinary tract it forms a UTI. If the infection doesn’t dissipate on its own and instead travels through the tract into the bladder, it can cause further damage. This means that it is important to treat a UTI as soon as symptoms appear.

Trimethoprim works by stopping bacteria from producing folate (folic acid, vitamin B). Folate produces DNA to spread the infection further, so controlling the production of folate is important to your recovery. Once the production of folate has been stopped, your body can fight the existing bacteria and get rid of the infection.

Once the spread of the bacteria has been halted, painful symptoms such as abdominal pain and a burning sensation in the urethra will ease quickly.

How do I take Trimethoprim?

Take one tablet twice a day, for three days. Aim to take the tablet at the same time each day (morning and evening).

How long does it take for Trimethoprim to start working?

When taking Trimethoprim, your symptoms should start to improve within 1 to 2 days. It is important to complete the full course, even if you feel better.

When should I stop taking Trimethoprim?

A normal course of Trimethoprim lasts for 3 days. In some cases, this may extend to 14 days. Never exceed the course length recommended by doctors.

What are the side effects of Trimethoprim?

Side effects of Trimethoprim may include a sore throat, rash, loss of appetite and diarrhoea. Please see the ‘side effects’ tab for more information.

Can I take Trimethoprim when pregnant?

Avoid taking Trimethoprim when pregnant unless absolutely necessary. It may be harmful to your baby.

Can I buy Trimethoprim online?

Yes - you can buy Trimethoprim online. You will need to complete an online consultation so that we can prescribe you with the treatment.


Medication Quantity Price

Patient Information

Before taking any medication, it is important to read the Patient Information Leaflet. You can find the information by searching for your treatment on Medicines.org.uk.

If you have any questions about your treatment please refer to Medicines.org.uk or contact us.

Trimethoprim Patient Information Leaflet

Latest product reviews from feefo


Excellent great service and very helpful

Read More


The antibiotics cleared the infection so I would use again.

Read More


Great quality medicine. Worked within specified time. Recommended.

Read More

Related guides and articles

Get your medication in three simple steps

Mouse pointer icon

1. Select treatment

Select your treatment with help from our A-Z guide or navigation bar.

2 people talking icon

2. Free consultation

Complete our free consultation. Complete privacy guaranteed.

Package icon

3. Discreet delivery

Pay for your treatment & enjoy discreet delivery. Next day delivery available.