Supplements and Diazepam.
Diazepam, sold under the brand name Valium, is a benzodiazepine: it potentiates GABA at the GABA-A receptor.
Diazepam is a benzodiazepine. The class potentiates GABA at the GABA-A receptor, producing sedation, anxiolysis, muscle relaxation, and anticonvulsant effects. UK general practice now prescribes mostly short courses for acute anxiety or sleep. Longer prescriptions are managed via specialist psychiatry, given the tolerance and dependence profile that emerges within four to six weeks of regular use. The supplement interactions that matter are additive sedation. Kava (where available, MHRA suspended 2003), valerian, magnesium glycinate at high doses (the glycine half rather than the magnesium drives the sedation), and CBD all stack on benzodiazepine effect. Alcohol is the combination most flagged in BNF and MHRA materials, given the additive respiratory depression. Lorazepam and temazepam are metabolised by glucuronidation rather than CYP, so most CYP-active supplements do not change their plasma levels. Diazepam runs through CYP3A4, so the standard 3A4 supplement interactions apply.
Below are the 8 documented pairs we have explicitly assessed against Diazepam in the Distil database: 1 red, 6 amber, and 1 green. The pairs cluster around 3 mechanisms: Additive CNS depression, Additive CNS sedation, and CYP3A4 induction. Every call is cited to either a clinical reference (PMID) or the British National Formulary. Anything not on this list is either still to be assessed or beyond our database scope. The checker beneath surfaces assessments by supplement, and the missing-item form at the bottom of the page routes any uncatalogued supplement into our next curation pass.
Documented interactions
Last reviewed 14 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 CNS depression
Red Does Kava interact with ?
Kava and diazepam both depress the central nervous system through overlapping pathways, and kava is independently linked to liver injury. Combining the two raises the risk of excessive sedation and adds to the liver-injury risk that already exists with kava alone. We treat this as a do-not-combine pair.
Evidence: Based on an established mechanism, with no direct study of this exact combination yet.
Reviewer-flagged: awaiting clinical-reviewer sign-off.
Amber Does Ashwagandha interact with ?
Ashwagandha can have a mild sedating effect on top of its main anti-stress action. Combined with diazepam, the sedation can stack. Use with care around driving or heavy machinery.
Evidence: Based on an established mechanism, with no direct study of this exact combination yet.
Reviewer-flagged: awaiting clinical-reviewer sign-off.
Amber Does Lemon Balm interact with ?
Lemon balm and diazepam both calm the nervous system through overlapping pathways. Combining them may mean stronger drowsiness, slower reaction time, and a heavier morning grogginess than either tends to give on its own. Use with care, particularly around driving.
Evidence: Limited human data, based on case reports and a known mechanism.
Amber Does Passionflower interact with ?
Passionflower and diazepam both calm the nervous system through overlapping pathways. Combining them can mean stronger drowsiness and slower reactions. Akhondzadeh 2001 found passionflower comparable to oxazepam for generalised anxiety, which gives you a sense of the additive potential.
Evidence: Limited human data, based on case reports and a known mechanism.
Amber Does Valerian Root interact with ?
Valerian and diazepam both promote sedation through overlapping pathways. Combining them can mean stronger drowsiness, slower reaction time, and a heavier morning hangover than either gives on its own. Use with care, particularly around driving.
Evidence: Limited human data, based on case reports and a known mechanism.
Green Does L-Theanine interact with ?
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.
Additive CNS sedation
Amber Does Melatonin interact with ?
Melatonin and diazepam can both promote drowsiness, so taking them together may add to the sedation and slow your reaction time more than either does alone. Use with care, particularly around driving or operating machinery.
Evidence: Based on an established mechanism, with no direct study of this exact combination yet.
Reviewer-flagged: awaiting clinical-reviewer sign-off.
CYP3A4 induction
Amber Does St John's Wort interact with ?
St John's Wort can speed up the breakdown of diazepam, which may mean it is less effective than expected at the prescribed dose. Talk to whoever prescribed it before combining.
Evidence: Limited human data, based on case reports and a known mechanism.
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 (food-supplement interactions only; for drug-drug interactions, the BNF is authoritative). Use the checker below to surface any supplement, and submit a missing item if you take something we have not catalogued.
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How we grade severity, choose what's in scope, and what we exclude.
Every call on this page is reasoned. We publish the full rubric for severity tiers, the medication inclusion logic, the evidence grades we accept, and what we deliberately leave out. About three thousand words. Worth reading once if you use this tool more than occasionally.
Read the full methodologyA 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.
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