L-Theanine and medications.
L-Theanine is in the Distil supplement database, evidence Grade B. The page below lists every medication we have explicitly assessed it against.
L-theanine is an amino acid found in tea that tends to promote a calm, settled state without sedating you. Its best-supported use is sleep onset, where the evidence sits at Grade B: a 2025 meta-analysis pooling eighteen trials found it modestly improved how quickly people felt they fell asleep and their overall sense of sleep quality, though the effects are small and mostly self-reported. The cognitive case is also Grade B. Two points of honesty about the trials. For anxiety, which theanine is widely sold for, the direct tests are negative: Sarris's randomised trial in diagnosed generalised anxiety found it did no better than placebo, and Zhang's network meta-analysis of herbal anxiety treatments reached the same conclusion, so we do not offer theanine for anxiety, general stress or attention difficulties. And in Haskell's focus study, theanine on its own did not help: it slightly worsened a mental arithmetic task and raised headache ratings, so the focus benefit belongs to the pairing with caffeine rather than to theanine alone. Typical doses are 100 to 200mg, with 200mg before bed for sleep onset and 100mg paired with caffeine at a roughly 4:1 theanine-to-caffeine ratio for focus. On interactions, caffeine is the standout positive pairing: theanine smooths the stimulation and reduces jitteriness, and it stacks well with magnesium glycinate for sleep. The one to watch is sedatives and benzodiazepines, where the effects on the central nervous system are additive. It is very well tolerated otherwise, with mild drowsiness only at higher doses alongside sedating compounds.
Below are the 3 documented pairs we have explicitly assessed for L-Theanine: 3 good to know. The pairs cluster around 2 mechanisms: Additive blood-pressure lowering and Additive CNS depression. Every call is cited to either a clinical reference (PMID) or the British National Formulary. Anything not listed here is either still to be assessed or beyond our database scope. The checker beneath surfaces assessments by medication, and the missing-item form at the bottom of the page routes any uncatalogued medication into our next curation pass.
Documented interactions
Last reviewed 15 June 2026. Each interaction below lists the evidence its assessment drew on: some rest on studies of the exact pair, others on mechanism evidence, where a citation may support one part of the reasoning rather than the exact combination. The evidence line on each entry says which.
Additive blood-pressure lowering
Good to know Does L-Theanine interact with Amlodipine?
In one small study, L-theanine took the edge off a stress-driven rise in blood pressure in some people, but it did not lower resting blood pressure the way a blood-pressure medicine does. At normal supplement doses it is not expected to push your blood pressure too low when taken with amlodipine. If you monitor at home and see readings lower than usual, mention it to your GP.
Evidence: Limited human data, from small studies or case reports.
Additive CNS depression
Good to know Does L-Theanine interact with Alprazolam?
L-theanine is calming but it does not act like a sedative, so it is not expected to add to the drowsiness of a benzodiazepine such as alprazolam. In a hospital trial it produced far less sedation than alprazolam itself and did not impair thinking. If you feel unusually drowsy on this combination, the cause is far more likely to be the alprazolam, and you should speak to your prescriber.
Evidence: Supported by human study data.
Good to know Does L-Theanine interact with Diazepam?
L-theanine is calming but it does not act like a sedative, so it is not expected to add to the drowsiness of a benzodiazepine such as diazepam. In a hospital trial it produced far less sedation than a benzodiazepine and did not impair thinking. If you feel unusually drowsy on this combination, the cause is far more likely to be the diazepam, and you should speak to your prescriber.
Evidence: Supported by human study data.
What this list does not say. Pairs not flagged here are not implicitly safe. They are either not yet in our database, or fall outside our inclusion scope. Use the checker below to surface any medication, and submit a missing item if you take something we have not catalogued.
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How the checker decides
Every result has a source
Each pair we have assessed is cited to a published study (PMID) or the British National Formulary, so you can read the source yourself.
Four kinds of answer
Severe, caution, no known interaction, and not yet assessed. A pair we have not assessed is never shown as clear.
- Severe
- Caution
- No known interaction
- Not yet assessed
Nothing in our data is not a clearance
When nothing in our data records a problem with a pair, the result says no known interaction at typical doses, which is not a clearance: your pharmacist or GP can check the pair against your full medical history.
A full supplement review, built around you, not a generic stack.
The free checker answers one interaction question at a time. A Distil report reviews the bigger picture: your goals, diet, medications, current supplements and any blood results you provide, then shows what appears worth keeping, changing, adding or leaving out.
- what your diet already covers, so you are not adding a capsule for something food is already handling
- which evidence-graded compounds are worth considering for your goals, and which were considered but left out
- what to keep, change or stop from what you already take, plus the order to introduce anything new
- how your medications and complete supplement stack fit together, with daily timing and a clear point for reassessment
The interaction check is one section of the full report. You also get the reasoning behind each recommendation and the evidence references used.
£49 until 30 June 2027 · £79 from 1 July 2027.
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