What the FDA labels say about taking them together
Isoniazid and metformin
Metformin's FDA label of September 3, 2026 names isoniazid in its drug interactions section; the isoniazid label PlainMeds reads does not name metformin.
Check it at the source: the isoniazid FDA label on DailyMed (effective July 8, 2025, OMNIVIUM PHARMACEUTICALS LLC.); the metformin FDA label on DailyMed (effective September 3, 2026, Granules India Ltd).
What does the isoniazid label say about metformin?
Isoniazid's label (effective July 8, 2025) does not name metformin in these sections. A label lists what its studies and reports found; it is not a complete list.
Source: FDA drug label (isoniazid), OMNIVIUM PHARMACEUTICALS LLC., effective July 8, 2025 (SPL set 35400f1d-fd25-4bfa-a382-ac390e21bf2e), via openFDA; the full label on DailyMed
What does the metformin label say about isoniazid?
Metformin label, drug interactionsClinical Impact: Certain drugs tend to produce hyperglycemia and may lead to loss of glycemic control. … estrogens, oral contraceptives, phenytoin, nicotinic acid, sympathomimetics, calcium channel blockers, and isoniazid.
Source: FDA drug label (Riomet, NDA021591), Sun Pharmaceutical Industries, Inc., effective December 6, 2018 (SPL set 05d4df4b-dfe8-4828-b423-a3d4f2c4114a), via openFDA
Source: FDA drug label (METFORMIN HYDROCHLORIDE), Granules India Ltd, effective September 3, 2026 (SPL set 73197cb5-3e23-4ac0-b189-f9bc848bce66), 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
| Isoniazid | Metformin | |
|---|---|---|
| Labeled for | n/a | Type 2 diabetes |
| Boxed warning | Yes | Yes |
| Pharmacy cost (NADAC) | $3.40 per tablet 300 mg tablet | $0.0145 per tablet 500 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