Ranked by how strong the human evidence is — best supported first.
Best supportedSleep qualityNot enough evidence· 1 sourceThen, in order
A root preparation from a Pacific pepper plant, traditionally drunk as a water-based beverage and sold in the West as an acetone or ethanol extract standardised to kavalactones.
Kava has genuine randomised trial evidence for anxiety and a genuine record of severe liver injury, including cases requiring transplantation. That combination led to bans and restrictions across Europe and elsewhere in the early 2000s. Extraction method appears to matter — traditional aqueous preparations have a longer safety record than the organic-solvent extracts implicated in many liver cases — but the question is not settled, and no test predicts who will be affected.
Regulation: Banned or severely restricted in Germany, Switzerland, France, Canada and the UK at various points following reports of hepatotoxicity; some restrictions have since been relaxed or overturned. The US FDA issued a consumer advisory about the risk of severe liver injury.
The amounts, forms and durations published trials of Kava actually administered.
These are the amounts published trials administered — not a recommendation, and not a dose to copy. Trial participants were screened, supervised and given a characterised preparation. What is in a retail bottle is frequently not what was studied, and the amount that suits one person is not general advice.
Studied for Anxiety
120–280 mg
Standardised extract, expressed as kavalactones per day, divided doses · 1–8 weeks
Trials rarely ran beyond eight weeks, so the dose range says nothing about longer use — which is precisely when the liver cases appeared. Solvent-extracted products differ from traditional water-based preparations.
This is general information about food, not medical advice. It cannot diagnose, treat or replace guidance from a clinician who knows your history.
Each window says whether a trial compared it against an alternative, or whether it is convention and pharmacology. Most timing advice is the second kind.
None of the timings below were directly compared in a trial. They reflect how the research happened to dose, or what the pharmacology implies — which is not the same as a timing being better.
Often taken in the evening because of sedation. Trials generally split the dose across the day without comparing schedules.
Timing was not directly compared. This reflects convention or how the compound behaves in the body, not a trial showing this window works better.
What each association actually rests on, and the papers behind it. A rating describes the state of the research, not how promising the supplement sounds. How we rate evidence.
Evidence is limited for kava and sleep specifically. Sleep improvements in trials were usually secondary to reduced anxiety rather than measured directly.
Not enough evidence. Not enough human research to say anything useful yet.
Meta-analysis · Drug safety · 2002 · PMID 11994028
Deep research mode adds each paper’s own conclusion and stated limitations.
Randomised trials and pooled analyses report reduced anxiety scores compared with placebo over several weeks, with effect sizes larger than most botanicals achieve. The safety record is the limiting factor rather than the efficacy data.
What may be going on: Kavalactones affect GABA-A receptor binding, sodium and calcium channels, and monoamine oxidase B in preclinical work.
Not enough evidence. Not enough human research to say anything useful yet.
Interactions, contraindications and dose limits, most serious first. Concentrated extracts interact with medication in ways the whole plant does not, so this section carries more weight here than it does on a food page.
Worth knowing
More than 100 reports of hepatotoxicity have been associated with kava, including hepatitis, cirrhosis, liver failure, transplantation and death. The reaction appears idiosyncratic and unpredictable, can occur within weeks, and is the reason for regulatory action in multiple countries.
Avoid
Interacts withAlcohol, paracetamol, statins, methotrexate, other hepatotoxic drugs
Combining kava with alcohol, paracetamol, statins, methotrexate or any hepatotoxic medication compounds a documented risk and should be avoided outright.
Interaction
Interacts withBenzodiazepines, alcohol, levodopa, anaesthetic agents
Kava adds strongly to benzodiazepines, alcohol and other sedatives, with reports of coma from the combination. It antagonises dopamine and can worsen Parkinson’s disease, and anaesthetists advise stopping at least 24 hours before surgery.
Worth knowing
Prolonged heavy use causes a distinctive dry, scaly rash, along with reported eye irritation and weight loss.
Avoid
Kava should not be used in pregnancy, while breastfeeding, or by anyone with existing liver disease. Impaired driving convictions have followed kava use, and its effects on coordination are real.