Isoniazid and Glimepiride: Interaction Details
AI-assisted, pharmacist-reviewed · Source data updated Aug 8, 2026 · Sources: FDA labeling, DDInter 2.0, cited literature
Isoniazid
No brand names on recordGlimepiride
How we grade severity & evidence
Severity levels
- Contraindicated: These should generally not be used together.
- Major: Potentially serious — often needs a change or close monitoring.
- Moderate: Can be significant — usually manageable with monitoring.
- Minor: Usually limited clinical impact.
Evidence grades
- Established: Well documented — supported by controlled studies or strong clinical data.
- Probable: Good supporting evidence, though not definitively proven.
- Suspected: Some evidence suggests this interaction, but it is not well established.
- Possible: Limited or conflicting evidence; the interaction may occur.
- Theoretical: Predicted from the drugs' pharmacology; not yet confirmed in people.
Ratings come from the documented interaction literature and are reviewed by a pharmacist. They describe the documented risk of the combination, not what will necessarily happen to you — your dose, timing, and health picture all matter.
What happens
Increased glimepiride exposure and risk of hypoglycemia
Interaction Deep Dive
Concomitant use of glimepiride (CYP2C9 substrate) and isoniazid (CYP2C9 inhibitor) may result in an increase in glimepiride exposure and the risk of hypoglycemia, especially in the elderly and patients with chronic renal failure and other acute illnesses. In a case report, the concomitant use of isoniazid and glimepiride in a 74-year-old woman with type 2 diabetes mellitus (T2DM) and latent TB resulted in hyperinsulinemic hypoglycemia1.
Why it happens (mechanism)
Inhibition of CYP2C9-mediated glimepiride metabolism by isoniazid
Literature reports
1 report — tap to read
a) The concomitant use of isoniazid and glimepiride in a 74-year-old woman with type 2 diabetes mellitus (T2DM) resulted in hyperinsulinemic hypoglycemia with serum glucose levels at 1.4 mmol/L, insulin levels at 37.17 micro international units/mL, and C peptide levels at 10.59 ng/mL. The patient's T2DM was well controlled for 8 years while receiving glimepiride 4 mg. One month following initiation of isoniazid for latent TB, she presented with severe hypoglycemia. Despite treatment with IV glucose, a second hypoglycemic event occurred and isoniazid treatment was discontinued. After 24 hours of discontinuing isoniazid, the hypoglycemia symptoms resolved and serum glucose levels normalized. The patient was discharged on glimepiride, pyrazinamide and ethambutol with no subsequent hypoglycemic events 1.
Common questions
Can I take Isoniazid and Glimepiride together?
Increased glimepiride exposure and risk of hypoglycemia Always confirm with your pharmacist or prescriber before making any change.
How serious is the Isoniazid and Glimepiride interaction?
It is rated major. Potentially serious — often needs a change or close monitoring.
How quickly could this interaction happen?
The documented onset is "delayed". Effects tend to build up gradually over days to weeks.
How strong is the evidence for this interaction?
The evidence is graded "probable". Good supporting evidence, though not definitively proven.
Questions for your pharmacist
- Does my dose of Isoniazid or Glimepiride need adjusting while I take them together?
- What symptoms should prompt me to call you or my prescriber right away?
- Does the timing of my doses matter for this combination?
- Is there a safer alternative to one of these medications for me?
References (1)
- Boglou P, Steiropoulos P, Papanas N, et al: Hypoglycaemia due to interaction of glimepiride with isoniazid in a patient with type 2 diabetes mellitus. BMJ Case Rep 2013; 2013:1. PubMed
Keep reading about Isoniazid
Keep reading about Glimepiride
These medications also interact with supplements
Prescription drugs aren't the whole picture — herbal and dietary supplements can interact with them too. From the evidence-graded Natural Medicines database:
major · moderate · minor — check everything you take with our drug–supplement interaction checker.
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