NutriStack
5-HTP and L-Tryptophan, contraindicated.
Both 5-HTP and L-Tryptophan increase serotonin synthesis. Combining them creates additive serotonin excess, risking serotonin syndrome.
One pair, every claim cited. The two substances, the type, the mechanism, the recommendation, and the primary literature.
Same shape as the other 1,729 pairs in the public database.
From the interaction database
What the row says.
Every entry follows the same shape: what is happening, the mechanism, the recommendation, and the primary literature.
At a glance
- Substances
- 5-HTP and L-Tryptophan
- Pair type
- Contraindicated
- Evidence (highest tier)
- Moderate
- Source citations
- 3 sources
- Stack Score effect
- −25 to your Stack Score (per scored contraindication row).
- Scope
- Supplement × Supplement
- Last verified
- May 30, 2026
Contraindicated · Moderate evidence
Contraindicated
What is happening. Both 5-HTP and L-Tryptophan increase serotonin synthesis. Combining them creates additive serotonin excess, risking serotonin syndrome.
Mechanism. 5-HTP bypasses rate-limiting tryptophan hydroxylase to directly flood serotonin synthesis. L-Tryptophan feeds the same pathway upstream. Combined effect causes dangerous serotonin accumulation.
Recommendation. Do NOT combine. Choose one serotonin precursor, not both.
Sources (3)
- Turner EH et al. Serotonin a la carte: supplementation with the serotonin precursor 5-hydroxytryptophan. Pharmacol Ther. 2006;109(3):325-38. PMID 16023217
- Fernstrom JD. A Perspective on the Safety of Supplemental Tryptophan Based on Its Metabolic Fates. J Nutr. 2016;146(12):2601S-2608S. PMID 27934651
- Boyer EW et al. The serotonin syndrome. N Engl J Med. 2005;352(11):1112-20. PMID 15784664
Stack Score
How this pair moves the number.
Effect on the composite score
If both 5-HTP and L-Tryptophan are in the same stack, this pair applies −25 to your Stack Score (per scored contraindication row).
The full algorithm, the clamping rules, and four worked stacks are documented at /methodology/stack-score.
Check your full routine
One pair was the worked example. NutriStack runs every pair in your stack at once.
Drop in your supplements and prescriptions and the public database surfaces every interaction, synergy, timing rule, and contraindication, every one linked to its primary source.