The short answer
Do not self-start L-5-HTP with mirtazapine. Official supplement guidance advises against its use with antidepressants; a timing gap has not been established as protection.
What this answer covers
Concentrated oral L-5-hydroxytryptophan, distinct from tryptophan and whole seed products.
- Supplement or preparation
- L-5-HTP
- Medication ingredient
- mirtazapine
The product guidance applies
Health Canada advises not to use L-5-HTP with antidepressants. Mirtazapine is an antidepressant, so the precaution is relevant.
Precursors are not interchangeable
L-5-HTP and L-tryptophan are different compounds. The mirtazapine label names tryptophan, while separate L-5-HTP guidance supplies this product’s warning.
Review the full mood regimen
Provide the amount, exact ingredient and other mood products to the prescriber. Do not use a dose gap as assurance that the combination is safe.
Recognize concerning symptoms
Seek urgent medical care for a combination of agitation or confusion, fever or heavy sweating, tremor, muscle rigidity or repeated twitching. These can be signs of serotonin syndrome; a single nonspecific symptom does not establish the diagnosis.
Evidence and practical considerations
Side effects & toxicity
Conditional review/avoidance follows explicit L-5-HTP antidepressant guidance, not a quantified mirtazapine-specific clinical event.
- Exact scope
- Concentrated oral L-5-hydroxytryptophan, distinct from tryptophan and whole seed products. with Exact oral mirtazapine tablets and orally disintegrating tablets. Exact oral mirtazapine in Remeron and RemeronSolTab; manufacturer label covers both. No equivalence to unrelated mirtazapine salts or other antidepressants inferred.
- Medication form and route
- oral
- Timing or duration
- Source-specific single-dose, repeated-dose and observational exposures distinguished.
What remains uncertain
- No exact original L-5-HTP co-use clinical event established in captured targeted literature.
Factors that may matter: preparation and plant part; clinical indication; dose; other medicines; baseline alertness.
Read the supporting source summaries
Source 1: current product label
dailymed.nlm.nih.gov · Source check Sep 10, 2026
Population: People prescribed oral mirtazapine.
Exact label names tryptophan and St John’s wort in serotonin warnings; CYP3A induction/inhibition may affect levels. Drowsiness and cognitive/motor impairment occur.
How this applies: Exact oral mirtazapine in Remeron and RemeronSolTab; manufacturer label covers both. No equivalence to unrelated mirtazapine salts or other antidepressants inferred.
No universal supplement interval, event rate or preparation equivalence established. Original label distinguishes warnings from measured pair-specific results.
Source 2: official product guidance
webprod.hc-sc.gc.ca · Source check Sep 10, 2026
Population: Adults considering oral L-5-HTP.
Advises not to use with antidepressants; gives serotonergic product precautions and drowsiness caution.
How this applies: The requested medicine is an antidepressant; this is a product-label precaution, not exact-pair clinical proof.
Does not quantify risk with each specific antidepressant or establish a safe supplement dose.
Research assessment: · Open full citations ↗
Review and change history
- Publication status
- Published research summary
- Clinical review
- Not yet recorded
| Date | Update |
|---|---|
| Article prepared | |
| Current exact available claims adjudicated using original captures and explicit identity and comparator limits. | |
| Research summary published |
Article revision: 1b3f33cd4258fc67
This guide brings together the evidence records used by our interaction checker. Each finding retains its own preparation limits, research date, and source summaries.
Full citations require verification. Reading this answer and the source summaries does not.
Taking other supplements or medications?
Use the checker to explore your other combinations. Ask a pharmacist to review the exact products, amounts and medical conditions in your complete list.
Open the interaction checkerInformation, not medical advice. Do not change prescribed treatment based on this guide.