What it's used for
Trimethoprim is used to treat or prevent infections proven or strongly suspected to be caused by susceptible bacteria.
Source: U.S. FDA-approved prescribing information (openFDA).
Typical dosing
The usual oral adult dosage is 100 mg every 12 hours or 200 mg every 24 hours for 10 days.
Dosing shown here is the general FDA-labeled range. Your prescribing clinician determines the exact dose, form, and schedule for you — this is not a substitute for medical advice.
Boxed warning / key safety info
Serious hypersensitivity reactions and interference with blood cell formation have been reported rarely.
Common side effects
The most frequently encountered adverse effects are rash, itching, and phototoxic skin eruptions.
Covered strengths on the Tab $0 list
Covered at $0 with an active Tab membership when filled at a participating pharmacy nationwide or through mail order. A licensed clinician must prescribe the medication.
Related medications
Other antibiotics & antivirals medications covered at $0 with an active Tab membership.
Trimethoprim cost without insurance
Cash prices for Trimethoprim without insurance vary widely by pharmacy, strength and quantity — the same prescription can cost very different amounts at two pharmacies in the same town. That is the problem a membership solves.
Trimethoprim is on Tab's covered $0 generic list. With an active Tab membership, every covered strength is $0 — not a percentage off, not a coupon that changes month to month — at participating pharmacies nationwide or through mail order. You do not need insurance, and Tab works whether or not you have a health plan.
Tab is a membership, not insurance. Covered medications require a prescription from a licensed clinician.
Trimethoprim dosage and administration
Sulfamethoxazole and trimethoprim tablets are contraindicated in pediatric patients less than 2 months of age. Urinary Tract Infections and Shigellosis in Adults and Pediatric Patients, and Acute Otitis Media in Children Adults The usual adult dosage in the treatment of urinary tract infections is 1 sulfamethoxazole and trimethoprim DS (double strength) tablet or 2 sulfamethoxazole and trimethoprim tablets every 12 hours for 10 to 14 days. An identical daily dosage is used for 5 days in the treatment of shigellosis. Children The recommended dose for children with urinary tract infections or acute otitis media is 40 mg/kg sulfamethoxazole and 8 mg/kg trimethoprim per 24 hours, given in two divided doses every 12 hours for 10 days. An identical daily dosage is used for 5 days in the treatment of shigellosis.
Excerpt from the FDA-approved prescribing information (openFDA), retrieved 2026-09-15. Your prescribing clinician decides the exact dose, form and schedule for you — this is not medical advice.
Trimethoprim side effects
The most common adverse effects are gastrointestinal disturbances (nausea, vomiting, anorexia) and allergic skin reactions (such as rash and urticaria). FATALITIES ASSOCIATED WITH THE ADMINISTRATION OF SULFONAMIDES, ALTHOUGH RARE, HAVE OCCURRED DUE TO SEVERE REACTIONS, INCLUDING STEVENS-JOHNSON SYNDROME, TOXIC EPIDERMAL NECROLYSIS, FULMINANT HEPATIC NECROSIS, AGRANULOCYTOSIS, APLASTIC ANEMIA AND OTHER BLOOD DYSCRASIAS (SEE WARNINGS SECTION). Hematologic Agranulocytosis, aplastic anemia, thrombocytopenia, leukopenia, neutropenia, hemolytic anemia, megaloblastic anemia, hypoprothrombinemia, methemoglobinemia, eosinophilia.
Excerpt from the FDA-approved prescribing information (openFDA), retrieved 2026-09-15. This is not a complete list. Report side effects to your clinician, and seek care for anything severe or unexpected.
Trimethoprim drug interactions
Potential for Sulfamethoxazole and Trimethoprim to Affect Other Drugs Trimethoprim is an inhibitor of CYP2C8 as well as OCT2 transporter. Sulfamethoxazole is an inhibitor of CYP2C9. Caution is recommended when sulfamethoxazole and trimethoprim is co-administered with drugs that are substrates of CYP2C8 and 2C9 or OCT2. In elderly patients concurrently receiving certain diuretics, primarily thiazides, an increased incidence of thrombocytopenia with purpura has been reported. It has been reported that sulfamethoxazole and trimethoprim may prolong the prothrombin time in patients who are receiving the anticoagulant warfarin (a CYP2C9 substrate). This interaction should be kept in mind when sulfamethoxazole and trimethoprim is given to patients already on anticoagulant therapy, and the coagulation time should be reassessed.
Excerpt from the FDA-approved prescribing information (openFDA), retrieved 2026-09-15. Tell your clinician and pharmacist about every medication, supplement and over-the-counter product you take.
Who should not take trimethoprim
Sulfamethoxazole and trimethoprim tablets are contraindicated in patients with a known hypersensitivity to trimethoprim or sulfonamides, in patients with a history of drug-induced immune thrombocytopenia with use of trimethoprim and/or sulfonamides, and in patients with documented megaloblastic anemia due to folate deficiency. Sulfamethoxazole and trimethoprim tablets are contraindicated in pediatric patients less than 2 months of age. Sulfamethoxazole and trimethoprim tablets are also contraindicated in patients with marked hepatic damage or with severe renal insufficiency when renal function status cannot be monitored.
Excerpt from the FDA-approved prescribing information (openFDA), retrieved 2026-09-15. Whether this medication is appropriate for you is a clinical decision made by your prescribing clinician.
Common questions
Is trimethoprim covered at $0 with Tab?
Yes. Trimethoprim is on Tab's covered $0 generic list — every covered strength is $0 with an active membership, at participating pharmacies nationwide or by mail order.
Do I need insurance to get trimethoprim through Tab?
No. Tab is a membership, not insurance. Covered medications are $0 with an active membership whether or not you have a health plan.
How do I get a trimethoprim prescription with Tab?
Book a video visit with a licensed Tab clinician (unlimited visits are included with membership). If it's clinically appropriate, they send the prescription to your chosen participating pharmacy or by mail order.
How much does trimethoprim cost without insurance?
Without insurance, retail cash prices for trimethoprim vary by pharmacy, strength and quantity. Trimethoprim is on Tab's covered $0 generic list, so every covered strength is $0 with an active Tab membership at participating pharmacies nationwide or by mail order.
What is the cheapest way to get trimethoprim?
For medications on Tab's covered list, a Tab membership is the cheapest route: covered strengths of trimethoprim are $0 with an active membership, and unlimited video visits with a licensed clinician are included, so the visit that produces the prescription is covered too.
What is the usual dose of trimethoprim?
Sulfamethoxazole and trimethoprim tablets are contraindicated in pediatric patients less than 2 months of age. (FDA-approved label, retrieved 2026-09-15. Your clinician sets your dose.)
What are the side effects of trimethoprim?
The most common adverse effects are gastrointestinal disturbances (nausea, vomiting, anorexia) and allergic skin reactions (such as rash and urticaria). (FDA-approved label, retrieved 2026-09-15.)
What interacts with trimethoprim?
Potential for Sulfamethoxazole and Trimethoprim to Affect Other Drugs Trimethoprim is an inhibitor of CYP2C8 as well as OCT2 transporter. Sulfamethoxazole is an inhibitor of CYP2C9. Caution is recommended when sulfamethoxazole and trimethoprim is co-administered with drugs that are substrates of CYP2C8 and 2C9 or OCT2. (FDA-approved label, retrieved 2026-09-15. Tell your clinician about every medication and supplement you take.)
Trimethoprim is $0 on the covered list
Members pay $0 for covered generics at participating pharmacies nationwide or by mail order — plus unlimited virtual primary care, urgent care and dermatology visits. No insurance needed.
Solo $49/mo · Family $119/mo for up to 4 people · Family+ $149/mo for up to 8
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