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Trimethoprim
In Stock
Friday, 03 Jul 2026
Medication features
Trimethoprim is an antibiotic prescribed to treat and prevent uncomplicated urinary tract infections (UTIs), such as cystitis.
- An effective antibiotic for treating many cases of cystitis
- Take 200mg twice daily for 3 days
- Read the patient leaflet for a full list of side effects, cautions, and interactions
Overview
NOTE: After selecting this product, you will need to complete a short assessment, so we can make sure this medication is suitable for you.
Buy Trimethoprim Online: Antibiotic for Cystitis
To order trimethoprim online for UK delivery:
- Check out the medical info on cystitis treatment.
- Answer some quick health questions to see if you qualify.
- Order reviewed by doctors, then sent from a UK pharmacy.
Trimethoprim is a prescription only antibiotic that offers effective relief from bacterial infections, particularly urinary tract infections in women. Whether you are dealing with an uncomfortable UTI or want protection against recurring infections, Trimethoprim halts bacteria growth and lets your immune system clear the infection.
Trimethoprim belongs to a drug class called antifolate antibiotics. It is available in the form of:
- Trimethoprim 100 mg tablets
- Trimethoprim 200 mg tablets
What is the recommended treatment duration for cystitis?
Generally given as a 3-day course for uncomplicated cystitis, though more severe cases may need a longer course. The full course must be completed to prevent bacterial resistance and recurrence. The full course must be completed to prevent bacterial resistance and recurrence.
Trimethoprim Drug Facts
- Brand names: Trimethoprim, Primsol, Proloprim, Trimpex
- Generic name: TMP, Trimethoprim
- Drug class: Anesthetics, Sulfonamides, Ophthalmic, Antifolate antibiotics, Other
- Controlled substance: No
- Generic status: Lower cost generic available
- Availability: Prescription only
How does it work?
Trimethoprim stops the growth of bacteria responsible for infections. It blocks the enzyme dihydrofolate reductase, which bacteria need to synthesize folic acid. Folic acid is an essential component for bacterial growth and reproduction. Without folic acid, bacteria cannot survive, helping to clear the infection.
As Trimethoprim prevents the production of folic acid, it may cause low folic acid levels in some people.
How effective is Trimethoprim?
Trimethoprim is effective for uncomplicated UTIs. Its cure rate is around 80-90%. However, its effectiveness depends on local antibiotic resistance patterns as its resistance is increasing in some areas.
Cystitis treatment duration
Generally given as a 3-day course for uncomplicated cystitis, with longer courses required for more severe infections. The full course must be completed to prevent bacterial resistance and recurrence.
Can you buy Trimethoprim over the counter?
Trimethoprim is a prescription medicine and is not available over the counter. You will need a Trimethoprim prescription from a professional doctor to access this medicine. You can buy Trimethoprim from a local or online pharmacy.
If you want to buy Trimethoprim tablets online and save time, consider Ashcroft Pharmacy. We offer free online consultations and medications at affordable rates.
Just fill out a short questionnaire, and one of our pharmacist team will evaluate whether this medicine is safe for you. Once approved, we will send Trimethoprim directly to your address with next-day delivery.
How to take Trimethoprim tablets for cystitis?
You must take Trimethoprim 200 mg for cystitis according to your doctor's guidelines such as:
A 3-day course of 200mg Trimethoprim twice daily (with 12 hours between doses) is generally effective for cystitis.
- Swallow the whole tablet with a glass of water.
- Do not crush, chew, or break the tablet.
- You can take this medicine with or without food, but it's best to take it with food to avoid side effects like nausea.
- Do not skip your doses as this medicine works well when there is a constant amount in the body.
- Do not take more or less than the prescribed dose.
Trimethoprim alternatives in the UK
In the last few years, antibiotic resistance to Trimethoprim has increased and around 30% of the bacteria which cause cystitis are now resistant to Trimethoprim. So if Trimethoprim for urinary tract infections does not suit you, you can consider other UTI medications such as:
- Nitrofurantoin
- Ciprofloxacin
- Fosfomycin
Trimethoprim vs. Nitrofurantoin
Trimethoprim and Nitrofurantoin are effective antibiotics for UTIs, but they differ in many aspects such as:
Trimethoprim has high resistance rates, while Nitrofurantoin is effective against common UTI-causing bacteria and is less likely to cause antibiotic resistance.
Trimethoprim is prescribed as 100mg or 200mg tablets, while Nitrofurantoin is prescribed as 50mg and 100mg tablets.
Trimethoprim is used to treat uncomplicated cystitis in women, ear infections, and kidney infections caused by specific bacteria. Nitrofurantoin is another good antibiotic for cystitis in the UK, specifically targeting urinary tract infections caused by susceptible bacteria.
Trimethoprim inhibits dihydrofolate reductase, preventing folic acid synthesis and ultimately killing them. On the other hand, Nitrofurantoin interferes with bacterial DNA, preventing their growth and ultimately killing them.
Although both medications are well tolerated for the most, the selection depends on your current health, age, and medical history. Consult your doctor for better advice.
How to store Trimethoprim tablets?
You must store this medicine at room temperature 68 F to 77 F (20 C to 25 C) in a closed container. Moreover:
- Keep it away from moisture, heat, and direct light.
- Do not store it in the bathroom.
- You can also expose this medicine to temperatures between 59 F to 86 F (15 C to 30 C) for shorter periods, such as when transporting it.
- Do not freeze your medications.
- Keep it away from the reach of children and pets.
- Discard the medicine that is expired or no longer needed via the medicine take-back program, protecting the environment, children, other people, and animals.
- If you still have concerns regarding the storage and disposal of this antibiotic, consult your doctor for better advice.
Directions
- Trimethoprim 200mg tablet is an antibiotic medication that's primarily indicated for the treatment of bacterial infections (UTI).
Dosage
Trimethoprim dosage for uncomplicated UTI:
- Take One Trimethoprim 200mg tablet, twice per day (morning & evening).
- Whether you are taking Trimethoprim for the short term (3 days) or long term (as prescribed), you must complete the course even if you begin to feel better to prevent reoccurrence or resistance.
Missed dose
If you forget to take a dose of this medicine, take it as soon as you remember. However, if it is too late or almost time for your next dose, skip the missed one and take your next dose at your regular dosing schedule. Do not take double or extra doses.
Overdose
If you or your child have taken too much Trimethoprim, there will be increased chances of nausea, dizziness, vomiting, depression, confusion, chills, or flu-like symptoms. In this case, you must seek emergency help or contact the Poison Control Center.
Warnings
Trimethoprim warnings
This medication is not suitable for everyone. You should not take it if you have:
- Mineral imbalance
- Diabetes
- An impaired or hepatic function
- Folate deficiency
- Liver or kidney disease
- Blood disorder
- Allergic reaction to Trimethoprim or any other ingredient present in this medicine
- High blood potassium levels
- Porphyria
- Megaloblastic anemia due to folate deficiency
- History of low levels of vitamin B-9 (folate)
- Are breastfeeding or pregnant
Besides these, if you have any other medical condition, tell your doctor before starting Trimethoprim to avoid serious complications.
Interactions
Trimethoprim may interact with prescription and over-the-counter medications, vitamins, supplements, minerals, and herbal products, leading to serious health complications. These medications include:
- Dofetilide.
- Procainamide (heart rhythm control).
- Repaglinide (diabetes).
- Digoxin (heart).
- Rifampicin (tuberculosis).
- Diuretics (water tablets).
- Warfarin-type anticoagulants (blood thinners requiring regular blood testing).
- Pyrimethamine and dapsone (malaria).
- Phenytoin (epilepsy).
- Colistimethate (cystic fibrosis).
- Immunosuppressant and bone marrow depressant drugs (including azathioprine, methotrexate, and ciclosporin).
- Levomethadyl.
- Chloroquine.
- Chlorpromazine.
- Cholera Vaccine, Live.
- Typhoid vaccines.
- Clarithromycin.
- Eplerenone.
- Erythromycin.
- Fluconazole
This is not a complete list. Share a complete list of medications you are taking or have taken with your doctor before taking Trimethoprim to determine whether this medicine is safe for you.
FAQ
Is Trimethoprim a strong antibiotic?
Trimethoprim is a moderately strong antibiotic against UTIs and some respiratory infections. It inhibits bacterial growth, but its effectiveness depends on bacterial resistance, which has increased in some regions.
What bacteria are killed by Trimethoprim?
Trimethoprim kills Escherichia coli (E.coli) which is the common cause of urinary tract infections. It is also effective against Gram-positive and Gram-negative bacteria such as Enterobacter, Klebsiella, Staphylococcus saprophyticus, and Proteus species. However, resistance to Trimethoprim has increased in some regions.
Is Trimethoprim bad for the kidneys?
Trimethoprim causes kidney problems, especially in people with pre-existing kidney disease. It increases the levels of potassium and creatinine, leading to severe complications. If you have kidney issues, consult your doctor before taking it.
Are trimethoprim and amoxicillin the same?
Trimethoprim and amoxicillin are not the same. Trimethoprim inhibits the synthesis of bacterial folic acid, while Amoxicillin is a beta-lactam antibiotic that disrupts bacterial cell walls. Trimethoprim is used for UTIs, while Amoxicillin treats dental abscesses, ear, skin, and respiratory infections. Consult your doctor to determine the right fit for you.
Why take Trimethoprim at night?
Trimethoprim is often taken at night or bedtime to enhance its effectiveness as urine production slows down during sleep, letting this antibiotic stay in the bladder longer and work better against infections. It also reduces the risk of possible side effects such as nausea.
Side Effects
Trimethoprim side effects
Trimethoprim tablets cause some side effects in some people. Its details are:
Common side effects
These effects are mild and short-lived. It occurs in more than 1 in 10 people. If they persist and get worse, consult your doctor.
- Itching
- Diarrhea
- A mild skin rash
- Vomiting
- Nausea
- Headache
- Thrush or sore mouth (glossitis)
- Stomach pain
- Increased sensitivity to sunlight (e.g., sunburn)
- Passing of gas
Serious side effects
It occurs in less than 1 in 1000 people and includes:
If you get any of these side effects, seek emergency help. Also, report side effects to Yellow Card.
- Allergic reaction, leading to anaphylaxis or angioedema: Its signs may include rash, hives, blisters, trouble breathing, or swelling of the face, lips, or tongue.
- Anemia: Its signs are pale skin, fatigue, and shortness of breath.
- Diarrhea that contains blood, mucus, and foul smell, caused by overgrowth of Clostridium difficile (C. diff).
- Blood problems such as low platelet levels (thrombocytopenia), low white blood cell levels (leukopenia), and low levels of a type of white blood cell called neutrophils (neutropenia).
- Unexplained bleeding.
- Severe diarrhoea.
- Unexplained bruising.
- General sickness.
- A high temperature.
Rare side effects
Rarely it causes some side effects such as:
If you get any of these side effects, seek emergency help. Also, report side effects to Yellow Card.
- Black, tarry stools or light-colored stools.
- Changes in skin color.
- Chest pain.
- Chills.
- Cough or hoarseness.
- Dark urine.
- Joint or muscle pain.
- Painful or difficult urination.
- Red irritated eyes.
- Red skin lesions, often with a purple center.
- Sores, ulcers, or white spots in the mouth or on lips.
- Swollen or painful glands.
- Unpleasant breath odor.
- Wheezing.
- Yellow eyes or skin.
- If you experience any of these side effects, seek medical help immediately.
How to cope with the side effects of Trimethoprim?
You can cope with its side effects in such a way that:
Nausea: Take Trimethoprim with food.
Diarrhea: Drink plenty of fluids to prevent dehydration. Take a probiotic along with trimethoprim.
Headache: Stay well hydrated and rest in a dark, quiet room. Drink at least 8 glasses of liquid such as tea, water, coffee, milk, soft drinks, and fruit juice every day. Take paracetamol and ibuprofen.
Increased sensitivity to sunlight: Wear sunscreen and protective clothing when going outside. Avoid direct sun exposure, especially between the hours of 10:00 a.m. and 3:00 p.m. Do not use a sunlamp or tanning bed or booth.
Itching or skin rash: Use an emollient cream or gentle, fragrance-free moisturizer, or take an antihistamine.
Anemia: take folic acid (a vitamin) every day.
Information
Ingredients
Trimethoprim ingredients
The ingredients in Trimethoprim antibiotic are:
- Active ingredient: Trimethoprim
- Inactive ingredients: Lactose monohydrate, microcrystalline cellulose, maize starch, sodium starch glycolate (Type A), colloidal anhydrous silica, povidone, stearic acid, magnesium stearate.
Delivery
Once your order has been approved by our UK medical team it will be dispatched via Royal mail. All orders are sent using a tracked and signed for service.
Royal Mail 48 (2-5 days) | £2.49
Estimated delivery within 2-3 working days. Excludes bank holidays. Not a guaranteed service.
Free standard delivery on orders over £45.
Royal Mail 24 (1-2 days) | £2.95
Estimated delivery within 1 working day. Excludes bank holidays. Not a guaranteed service.
Royal Mail Special Delivery Guaranteed by 1pm | £6.99
Order by the 2:00 PM weekday cut-off time for guaranteed delivery by 1:00 PM the next business day.
Orders placed after the cut-off on Friday will be delivered on Tuesday.
Price Comparison
| Medication | Ashcroft Pharmacy |
|---|---|
| 200mg x6 | £9.99
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Written and reviewed by our qualified team
Authored by:
Mr Suhail Jamil
Superintendent Pharmacist
GPhC Number: 2069518
Order Monday to Friday before 14:00pm to guarantee next day delivery
