L-Tryptophan and medications.
L-Tryptophan is not in the Distil recommendation database. We surface it here deliberately, because why a compound is left out is as useful as what we recommend.
L-tryptophan is the raw material your body turns into serotonin, so it raises serotonin from the supply side. That puts it in the same bracket as 5-HTP. Combined with an SSRI or SNRI it can tip into serotonin excess, and there are published cases of toxic reactions when tryptophan was added to antidepressants. With an MAOI like phenelzine the combination has caused serious reactions and is a clear do-not-combine.
As with 5-HTP, the people most likely to try tryptophan for mood or sleep are often already on a serotonergic medicine, so we exclude it rather than recommend it with a warning. The documented pairs below show why. If sleep or mood is what you are after, the options below do not load serotonin.
What to consider instead. Every option below is in the Distil database, so you can check each against your own medications:
- Magnesium Glycinate: the glycine half does most of the calming; no serotonergic action
- Glycine: 3g at bedtime, lowers core temperature and tends to ease sleep onset
- Saffron Extract: for the mood angle, with antidepressant trial evidence
We still hold the documented interactions for L-Tryptophan, which is why it stays in the interactions checker even though we do not recommend it. Below are the 28 documented pairs we have explicitly assessed: 7 red and 21 amber. Every call is cited to a clinical reference (PMID) or the British National Formulary.
Documented interactions
Last reviewed 30 June 2026. Each interaction below is assessed against PubMed-indexed evidence.
Additive serotonergic activity
Red Does interact with Isocarboxazid?
Tryptophan is the building block your body uses to make serotonin, and isocarboxazid is an MAOI that blocks serotonin breakdown. Combining them can drive serotonin to dangerous levels and has caused toxic reactions in published cases. Do not combine.
Evidence: Supported by human study data.
Red Does interact with Linezolid?
Tryptophan is the building block your body uses to make serotonin, and linezolid is an antibiotic that also acts as an MAOI, blocking serotonin breakdown. Combining them can drive serotonin to dangerous levels and has caused toxic reactions in published cases. Do not combine.
Evidence: Supported by human study data.
Red Does interact with Moclobemide?
Tryptophan is the building block your body uses to make serotonin, and moclobemide is an MAOI (the reversible kind) that blocks serotonin breakdown. Combining them can drive serotonin to dangerous levels and has been named as a cause of serotonin syndrome. Do not combine.
Evidence: Supported by human study data.
Red Does interact with Phenelzine?
Tryptophan is the building block your body uses to make serotonin, and phenelzine is an MAOI that blocks serotonin breakdown. Combining them can drive serotonin to dangerous levels and has caused toxic reactions in published cases. Do not combine.
Evidence: Supported by human study data.
Red Does interact with Rasagiline?
Taking L-tryptophan with rasagiline (an MAO-B inhibitor used for Parkinson's) can push serotonin to dangerous levels, because there is less MAO available to break it down, so we treat this as a do-not-combine pair. The combination has caused serotonin syndrome in case reports with other MAO inhibitors.
Evidence: Based on an established mechanism, with no direct study of this exact combination yet.
Reviewer-flagged: awaiting clinical-reviewer sign-off.
Red Does interact with Selegiline?
Taking L-tryptophan with selegiline (an MAO-B inhibitor used for Parkinson's) can push serotonin to dangerous levels, because there is less MAO available to break it down, so we treat this as a do-not-combine pair. The combination has caused serotonin syndrome in case reports with other MAO inhibitors.
Evidence: Based on an established mechanism, with no direct study of this exact combination yet.
Reviewer-flagged: awaiting clinical-reviewer sign-off.
Red Does interact with Tranylcypromine?
Tryptophan is the building block your body uses to make serotonin, and tranylcypromine is an MAOI that blocks serotonin breakdown. Combining them can drive serotonin to dangerous levels and has caused toxic reactions in published cases with this drug class. Do not combine.
Evidence: Supported by human study data.
Amber Does interact with Amitriptyline?
Tryptophan is the building block your body uses to make serotonin, and amitriptyline raises serotonin and noradrenaline. Taking them together raises serotonin from both directions and the effect can add up. Watch for agitation, sweating, tremor, shivering, or muscle twitching, and discuss with your GP before stacking.
Evidence: Limited human data, based on case reports and a known mechanism.
Amber Does interact with Citalopram?
Tryptophan is the building block your body uses to make serotonin, so adding it to citalopram raises serotonin from both directions. The combination can cause agitation, sweating, tremor, shivering, muscle twitching, or a racing heart. Do not stack them without your GP's involvement.
Evidence: Limited human data, based on case reports and a known mechanism.
Reviewer-flagged: awaiting clinical-reviewer sign-off.
Amber Does interact with Clomipramine?
Tryptophan is the building block your body uses to make serotonin, and clomipramine is the most strongly serotonin-acting of the tricyclics. Taking them together raises serotonin from both directions and is more likely to add up than with the other tricyclics. Watch for agitation, sweating, tremor, shivering, or muscle twitching, and do not stack them without your GP's involvement.
Evidence: Limited human data, based on case reports and a known mechanism.
Reviewer-flagged: awaiting clinical-reviewer sign-off.
Amber Does interact with Dosulepin?
Tryptophan is the building block your body uses to make serotonin, and dosulepin raises serotonin and noradrenaline. Taking them together raises serotonin from both directions and the effect can add up. Watch for agitation, sweating, tremor, shivering, or muscle twitching, and discuss with your GP before stacking.
Evidence: Limited human data, based on case reports and a known mechanism.
Amber Does interact with Doxepin?
Tryptophan is the building block your body uses to make serotonin, and doxepin raises serotonin and noradrenaline. Taking them together raises serotonin from both directions and the effect can add up. Watch for agitation, sweating, tremor, shivering, or muscle twitching, and discuss with your GP before stacking.
Evidence: Limited human data, based on case reports and a known mechanism.
Amber Does interact with Duloxetine hydrochloride?
Tryptophan is the building block your body uses to make serotonin, so adding it to duloxetine raises serotonin from both directions. The combination can cause agitation, sweating, tremor, shivering, muscle twitching, or a racing heart. Do not stack them without your GP's involvement.
Evidence: Limited human data, based on case reports and a known mechanism.
Reviewer-flagged: awaiting clinical-reviewer sign-off.
Amber Does interact with Escitalopram?
Tryptophan is the building block your body uses to make serotonin, so adding it to escitalopram raises serotonin from both directions. The combination can cause agitation, sweating, tremor, shivering, muscle twitching, or a racing heart. Do not stack them without your GP's involvement.
Evidence: Limited human data, based on case reports and a known mechanism.
Reviewer-flagged: awaiting clinical-reviewer sign-off.
Amber Does interact with Fluoxetine hydrochloride?
Tryptophan is the building block your body uses to make serotonin, so adding it to fluoxetine raises serotonin from both directions. The combination can cause agitation, sweating, tremor, shivering, muscle twitching, or a racing heart. Do not stack them without your GP's involvement.
Evidence: Supported by human study data.
Amber Does interact with Fluvoxamine?
Tryptophan is the building block your body uses to make serotonin, so adding it to fluvoxamine raises serotonin from both directions. The combination can cause agitation, sweating, tremor, shivering, muscle twitching, or a racing heart. Do not stack them without your GP's involvement.
Evidence: Limited human data, based on case reports and a known mechanism.
Reviewer-flagged: awaiting clinical-reviewer sign-off.
Amber Does interact with Imipramine?
Tryptophan is the building block your body uses to make serotonin, and imipramine raises serotonin and noradrenaline. Taking them together raises serotonin from both directions and the effect can add up. Watch for agitation, sweating, tremor, shivering, or muscle twitching, and discuss with your GP before stacking.
Evidence: Limited human data, based on case reports and a known mechanism.
Amber Does interact with Lithium carbonate?
Tryptophan raises serotonin, and lithium increases your brain's response to serotonin. Used together they can add up, which may cause agitation, sweating, tremor, shivering, muscle twitching, or a racing heart. Do not stack them without your GP's involvement.
Evidence: Limited human data, based on case reports and a known mechanism.
Reviewer-flagged: awaiting clinical-reviewer sign-off.
Amber Does interact with Lofepramine?
Tryptophan is the building block your body uses to make serotonin, while lofepramine works mainly on noradrenaline and has only weak serotonin activity. Any added serotonin effect is likely to be small, but it is worth mentioning the tryptophan to your GP and watching for restlessness, sweating, or shivering if your dose has recently changed.
Evidence: Based on an established mechanism, with no direct study of this exact combination yet.
Reviewer-flagged: awaiting clinical-reviewer sign-off.
Amber Does interact with Nortriptyline?
Tryptophan is the building block your body uses to make serotonin, while nortriptyline works mainly on noradrenaline and has only weak serotonin activity. Any added serotonin effect is likely to be small, but it is worth mentioning the tryptophan to your GP and watching for restlessness, sweating, or shivering if your dose has recently changed.
Evidence: Based on an established mechanism, with no direct study of this exact combination yet.
Reviewer-flagged: awaiting clinical-reviewer sign-off.
Amber Does interact with Paroxetine hydrochloride?
Tryptophan is the building block your body uses to make serotonin, so adding it to paroxetine raises serotonin from both directions. The combination can cause agitation, sweating, tremor, shivering, muscle twitching, or a racing heart. Do not stack them without your GP's involvement.
Evidence: Limited human data, based on case reports and a known mechanism.
Reviewer-flagged: awaiting clinical-reviewer sign-off.
Amber Does interact with Sertraline?
Tryptophan is the building block your body uses to make serotonin, so adding it to sertraline raises serotonin from both directions. The combination can cause agitation, sweating, tremor, shivering, muscle twitching, or a racing heart. Do not stack them without your GP's involvement.
Evidence: Limited human data, based on case reports and a known mechanism.
Reviewer-flagged: awaiting clinical-reviewer sign-off.
Amber Does interact with Sumatriptan succinate?
Tryptophan is the building block your body uses to make serotonin, and sumatriptan is a serotonin-receptor drug used for migraine. In theory the two together could raise serotonin activity. The real-world risk looks low and most people tolerate the combination, but be alert to symptoms like agitation, sweating, shivering, tremor, muscle twitching, or a racing heart, and mention the tryptophan to your GP, especially if you also take an antidepressant.
Evidence: Limited human data, based on case reports and a known mechanism.
Reviewer-flagged: awaiting clinical-reviewer sign-off.
Amber Does interact with Tramadol hydrochloride?
Tryptophan is the building block your body turns into serotonin, and tramadol raises serotonin as part of how it relieves pain. Taking them together may increase the risk of serotonin syndrome (agitation, sweating, tremor, shivering, muscle twitching, a racing heart). Do not stack them without your prescriber's involvement, especially around a dose change.
Evidence: Supported by human study data.
Reviewer-flagged: awaiting clinical-reviewer sign-off.
Amber Does interact with Trazodone hydrochloride?
Tryptophan is the building block your body uses to make serotonin, so adding it to trazodone raises serotonin from both directions. The combination can cause agitation, sweating, tremor, shivering, muscle twitching, or a racing heart. Do not stack them without your GP's involvement.
Evidence: Limited human data, based on case reports and a known mechanism.
Reviewer-flagged: awaiting clinical-reviewer sign-off.
Amber Does interact with Venlafaxine?
Tryptophan is the building block your body uses to make serotonin, so adding it to venlafaxine raises serotonin from both directions. The combination can cause agitation, sweating, tremor, shivering, muscle twitching, or a racing heart. Do not stack them without your GP's involvement.
Evidence: Limited human data, based on case reports and a known mechanism.
Reviewer-flagged: awaiting clinical-reviewer sign-off.
Amber Does interact with Vortioxetine?
Tryptophan is the building block your body uses to make serotonin, so adding it to vortioxetine raises serotonin from both directions. The combination can cause agitation, sweating, tremor, shivering, muscle twitching, or a racing heart. Do not stack them without your GP's involvement.
Evidence: Limited human data, based on case reports and a known mechanism.
Reviewer-flagged: awaiting clinical-reviewer sign-off.
Amber Does interact with Zolmitriptan?
Tryptophan is the building block your body uses to make serotonin, and zolmitriptan is a serotonin-receptor drug used for migraine. In theory the two together could raise serotonin activity. The real-world risk looks low and most people tolerate the combination, but be alert to symptoms like agitation, sweating, shivering, tremor, muscle twitching, or a racing heart, and mention the tryptophan to your GP, especially if you also take an antidepressant.
Evidence: Limited human data, based on case reports and a known mechanism.
Reviewer-flagged: awaiting clinical-reviewer sign-off.
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