Drug & supplement interaction

L-tryptophan + Levetiracetam

Levetiracetam brand names: Keppra, Elepsia XR, Spritam.

Major Interaction
Medically reviewed by · Updated September 2026
The bottom line Major

L-tryptophan has a major interaction with Levetiracetam. Theoretically, concomitant use of L-tryptophan with CNS depressants might cause additive sedative effects.

Read the full interaction report
SeverityMajor
LikelihoodProbable
EvidenceB
What do Severity, Likelihood & Evidence mean?
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Interaction report

L-tryptophan and Levetiracetam

Here is the interaction we found between these two, with the evidence behind it.

Major

CNS DEPRESSANTS

Why this applies to Levetiracetam

Levetiracetam falls under CNS DEPRESSANTS — the group L-tryptophan interacts with.

Theoretically, concomitant use of L-tryptophan with CNS depressants might cause additive sedative effects.
Clinical research shows that L-tryptophan can cause fatigue and drowsiness.
Severity Major Likelihood Probable Evidence B

Interaction has not been documented in well-controlled studies, however, the interaction has been demonstrated in some small human studies or in controlled animal studies in conjunction with multiple case reports..

Dr. Brian Staiger, PharmD, BCPS
Dr. Brian Staiger explains PharmD, Clinical Pharmacist

Here's the thing to keep in mind with this pairing. Levetiracetam (Keppra) already tends to cause drowsiness, tiredness, and sometimes that foggy or slowed-down feeling on its own. L-tryptophan can also make people feel sleepy and fatigued because your body turns it into serotonin and then melatonin. So this isn't about one changing how the other is broken down. It's simply that two things that both calm the brain can stack on top of each other.

Put them together and you may feel more sleepy, more sluggish, or less alert than usual, which matters if you drive or operate machinery. This is rated as a real (probable) concern, though much of it is reasoned from how these act rather than proven head-to-head. Please check with your pharmacist or doctor before adding tryptophan, and don't change your Keppra dose on your own.

Contact Dr. Brian directly if you have additional questions on this interaction
References
  1. Lieberman HR, Corkin S, Spring BJ. The effects of dietary neurotransmitter precursors on human behavior. Am J Clin Nutr 1985;42:366-70. PubMed

What These Ratings Mean

Every interaction above is graded three ways — here’s the key to each label.

Severity how clinically significant the interaction is
Major

Clinically significant. Avoid the combination, or use only under close professional supervision.

Moderate

Usually worth avoiding or managing — may need monitoring, a dose change, or timing apart.

Minor

Generally not serious. Be aware of it and mention it to your pharmacist.

Likelihood how strong the evidence is that the interaction actually happens in people
  • LikelyWell-controlled human studies have demonstrated the likely existence of this interaction.
  • ProbableInteraction has not been documented in well-controlled studies, however, the interaction has been demonstrated in some small human studies or in controlled animal studies in conjunction with multiple case reports.
  • PossibleInteraction has been documented in animal or in lab research, or the interaction has been documented in humans but is limited to case reports or conflicting clinical research exists.
  • UnlikelyInteraction has been demonstrated in animal or in lab research but has been shown not to occur in humans.
Evidence the quality of the studies behind the rating (graded A–D)
  • AHigh-quality meta-analysis (quantitative systematic review).
  • BCase-control study.
  • CConsensus.
  • DAnecdotal evidence.

These ratings are for information only. Never start, stop, or otherwise change your therapy before speaking with your provider.

Keep it in perspective

L-tryptophan Also Interacts With Other Medications

L-tryptophan has 247 major, 146 moderate known drug interactions in our database — the Levetiracetam one above is one of them. If you take anything else, check it against the full list below.

Major 247 Moderate 146 No known interaction 2,437 (incl. Levetiracetam)
Taking anything else?

Check Another of Your Medications Against L-tryptophan

Covers the 2,830 medications we’ve checked against L-tryptophan. Pick one to open its full report.

From our Q&A

Questions About L-tryptophan or Levetiracetam

These are real questions from readers, answered by the pharmacists at HelloPharmacist — written by a person, not generated from a database. Each one covers L-tryptophan or Levetiracetam, not necessarily both, but if one is close to what you were about to ask it will usually go further than a database entry can:

Not quite your question? Ask our pharmacists directly — it is free, there is no account required, and answers usually come back within 24 hours.

Everything else you take

See Every Supplement That Interacts With Levetiracetam

This page covers L-tryptophan only. If you take other supplements — a multivitamin, a sleep aid, something for joints — the Levetiracetam page lists 105 supplements it has a documented interaction with, worst first, each one explained.

The most serious there right now: 1,4-butanediol (major), Activated Charcoal (major), Beer (major), Gamma-hydroxybutyrate (ghb) (major) and Kava (major).

By severity: 7 major · 82 moderate · 16 minor.

From our pharmacist’s overview on the Levetiracetam page

“I would read this page carefully rather than casually. Levetiracetam (Keppra, Spritam) controls seizures, and both hazards on this list run through that fact.”

Reviewed by 2 · Jul 18, 2026

Open the Levetiracetam interaction page

One more smart check

Taking L-tryptophan as Part of a Dietary Supplement Product? Check It for Interactions

We hold 5 real supplement products containing L-tryptophan, each one broken down to its full ingredient list — and combination products often carry several ingredients besides L-tryptophan. Your product may carry other ingredients that interact with Levetiracetam too, on top of L-tryptophan — and those would not show on this page. Find your product and we’ll check every ingredient on its label:

How much people look this up

Where L-tryptophan and Levetiracetam Sit Against Everything Else

Out of every supplement and medication people look up on HelloPharmacist, here is where these two land this week — and which way each has been moving.

Supplement L-tryptophan
Steady interest

#932 of 1,452 supplements looked up here in the last 7 days

29 days ago today
Medication Levetiracetam
Top 10%

#250 of 2,830 medications looked up here in the last 7 days

29 days ago today

Position among everything looked up on this site, not a measure of how commonly either one is used or how important it is. A supplement can climb this list because of a news story. It counts every request to the page, automated ones included, and nothing here identifies anyone.

Supplement

About L-tryptophan

What is L-tryptophan?

L-tryptophan
  • Sleep problems
  • Low mood and depression
  • Anxiety
  • Premenstrual symptoms
  • Appetite and food cravings

L-tryptophan is an essential amino acid the body uses to make serotonin and melatonin, and people take it to support sleep and mood. The evidence for supplement use is limited and mixed, and there are real safety concerns, so talk to a pharmacist or doctor before trying it.

Read the full L-tryptophan monograph & all interactions
Medication

About Levetiracetam

What Is Levetiracetam Used For?

Brand names: Keppra, Elepsia XR, Spritam

Levetiracetam is used to treat several types of seizures. It treats partial-onset seizures (seizures that start in one area of the brain) and is used as add-on therapy for myoclonic seizures (sudden, brief muscle jerks) in people with juvenile myoclonic epilepsy aged 12 and older, and for primary generalized tonic-clonic seizures (grand mal seizures) in people with idiopathic generalized epilepsy aged 6 and older.

Age eligibility varies by product. Keppra oral and Roweepra tablets treat partial-onset seizures in patients as young as 1 month. Spritam and levetiracetam tablets for oral suspension treat partial-onset seizures in patients 4 years and older weighing more than 20 kg. Extended-release products — including Elepsia XR, Keppra XR, and Levetiracetam ER — are approved only for partial-onset seizures in patients 12 years and older. Injectable forms are used intravenously when a patient temporarily cannot take oral medication.

See full Levetiracetam drug information
Keep checking

Other Drugs & L-tryptophan

Browse every other medication we’ve checked against L-tryptophan — both the ones with a known interaction and the ones without. Select any drug for the full detail.

247Major
146Moderate
0Minor
2,436No known interaction
247 Major 146 Moderate 2,436 No interaction
Major

247 interactions

Showing 60 of 247 major interactions — see all 247 on the L-tryptophan page.

Moderate

146 interactions

Showing 60 of 146 moderate interactions — see all 146 on the L-tryptophan page.

No interaction 2,436 drugs checked — show the list

We also checked L-tryptophan against these medications and found no known interaction in our sources. Open any page to confirm.

Showing the 60 most looked-up of 2,436 medications checked with no known interaction — see the full L-tryptophan list.

See the full L-tryptophan interactions page
See every supplement checked against Levetiracetam, ranked by severity
Sources

Sources & How We Checked

Interaction details are evidence-graded and sourced from the Natural Medicines database. The medication overview comes from MedlinePlus.

Content is written and reviewed by licensed HelloPharmacist pharmacists. See our data sources and editorial standards for how this information is built and checked.

Parts of this content are provided by the Therapeutic Research Center, LLC.

DISCLAIMER: Currently this does not check for drug-drug interactions. This is not an all-inclusive comprehensive list of potential interactions and is for informational purposes only. Not all interactions are known or well-reported in the scientific literature, and new interactions are continually being reported. Input is needed from a qualified healthcare provider including a pharmacist before starting any therapy. Application of clinical judgment is necessary.

© 2021 Therapeutic Research Center, LLC

Keep exploring
L-tryptophan monograph › Uses, safety, and every drug interaction in one place Levetiracetam supplement interactions › Every supplement checked against Levetiracetam, ranked by severity Levetiracetam drug information › The full plain-English guide to this medication Supplement interaction checker › Check any supplement or product against your medications Browse medications A–Z › Every drug we've checked against herbs & supplements Ask a pharmacist › Free, personal answer from our licensed team
Pharmacist Counseling Corner

Taking L-tryptophan and Levetiracetam Together: Common Questions

Can you take L-tryptophan with Levetiracetam?
This is rated a major interaction, so the combination is best avoided unless your doctor or pharmacist has specifically told you otherwise. Read the full details on this page and confirm with your pharmacist before combining them.
How serious is the L-tryptophan and Levetiracetam interaction?
We rate it Major. This is a clinically significant combination that is generally best avoided, or used only under the direct supervision of your physician or pharmacist.

Written and reviewed by the HelloPharmacist editorial staff. Our editorial policy

Still Have a Question About Levetiracetam and L-tryptophan?

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This information is for education only and is not a substitute for professional medical advice. Always check with your pharmacist or doctor before starting, stopping, or combining supplements and medications.