What the FDA labels say about taking them together
Folic acid and trimethoprim
Folic acid's FDA label (Folic Acid) of February 11, 2026 names trimethoprim in its drug interactions section; the trimethoprim label PlainMeds reads does not name folic acid.
Check it at the source: the folic acid FDA label on DailyMed (effective July 24, 2026, Rising Pharma Holdings, Inc.); the trimethoprim FDA label on DailyMed (effective January 26, 2024, Dr. Reddy's Labratories Inc.).
What does the folic acid label say about trimethoprim?
Folic Acid label (Ayurax, LLC, February 11, 2026), drug interactionsSeveral antifolate agents, including trimethoprim, pyrimethamine, methotrexate, and triamterene, directly inhibit dihydrofolate reductase, decreasing the formation of active folate derivatives.
Source: FDA drug label (Folic Acid, NDA216395), Ayurax, LLC, effective February 11, 2026 (SPL set 96618bf8-6c03-4df3-9896-b7ef27ca392a), via openFDA
Source: FDA drug label (Folic Acid), Rising Pharma Holdings, Inc., effective July 24, 2026 (SPL set 0baa10dd-6d1d-4946-8236-566451132da3), via openFDA; the full label on DailyMed
What does the trimethoprim label say about folic acid?
Trimethoprim's label (effective January 26, 2024) does not name folic acid in these sections. A label lists what its studies and reports found; it is not a complete list.
Source: FDA drug label (Trimethoprim), NDA018679 (Dr Reddys Labs Sa), as published by Dr. Reddy's Labratories Inc., effective January 26, 2024 (SPL set 73ccebc1-7412-2424-d62c-a5180ec52d81), via openFDA; the full label on DailyMed
These are the labels' own sentences. PlainMeds does not grade interactions; a pharmacist or prescriber can say what they mean for one person's medicines.
Both medicines on the record
| Folic acid | Trimethoprim | |
|---|---|---|
| Labeled for | n/a | Bacterial infections, Urinary tract infections |
| Boxed warning | No | No |
| Pharmacy cost (NADAC) | $0.0201 per tablet 1 mg tablet | $1.31 per tablet 100 mg tablet |
| Shortage now | No current entry | No current entry |
Source: FDA NDC Directory, CMS NADAC of October 7, 2026 and the FDA Drug Shortage Database (FDA files October 8, 2026)
What next?
- Check more medicines together
- up to five at once