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
Additive CNS depression
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.
Reviewer-flagged: awaiting clinical-reviewer sign-off.
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.
Reviewer-flagged: awaiting clinical-reviewer sign-off.
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.
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.
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.
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.
Additive CNS sedation
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.
Reviewer-flagged: awaiting clinical-reviewer sign-off.
CYP3A4 induction
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.
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.
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 methodologyWant this checked across everything you take?
This page checks the pairs you enter. The personalised Distil report goes further:
- the same graded, cited interaction check across your whole stack, not just the pairs you thought to type in
- where your current routine may be leaving you short of your goals
- the evidence-backed compounds worth adding, and the ones worth dropping
It's a paid report: £79, or £49 for the first 25 customers. The interactions check is one section of it, and you can read a real one in full before you buy.
See a real sample reportSomething missing?
If a supplement or medication you take isn't in our autocomplete, tell us. We go through what people flag every week and add what's missing.