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Moderate evidenceStress & mood

Kava

Older meta-analytic data show kava beats placebo for anxiety, but the largest and best-conducted modern trial was flatly negative — and the drug carries a genuine, regulator-recognised hepatotoxicity signal. The risk-benefit case is much weaker than kava's popularity implies.

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What the science says

  • Reduces anxiety symptoms Moderate evidence

    A Cochrane review of 12 double-blind trials found kava extract superior to placebo, with a pooled Hamilton Anxiety Rating Scale advantage of roughly 3.9 points (95% CI 0.1-7.7) — statistically significant but with a confidence interval brushing zero, and drawn mostly from small, short trials.

  • Effective for diagnosed generalised anxiety disorder Limited evidence

    The largest dedicated trial (K-GAD, 171 patients, 16 weeks, 240 mg kavalactones/day of an aqueous extract) found no significant difference from placebo on anxiety outcomes, and reported more liver-enzyme elevations in the kava arm. An earlier, much smaller 6-week trial by the same group had been positive, so the modern data are best described as mixed-to-negative.

  • Acts without the dependence liability of benzodiazepines Limited evidence

    Kavalactones modulate GABA-A allosterically and act on sodium and calcium channels without the classic benzodiazepine binding site, and trials have not reported withdrawal syndromes. However, no long-term controlled study has formally assessed dependence, tolerance or cognitive effects, so this is a mechanistic argument rather than a demonstrated one.

Dosage & safety

Studied doseTrials used 120-280 mg of kavalactones per day, most commonly 240 mg/day, in divided doses for 4-16 weeks. Traditional water-based (aqueous) extracts of noble kava root are preferred; acetone and ethanol extracts and preparations using stems, leaves or peelings are associated with most of the reported liver injury. Kavalactone content is what matters — raw root powder weight tells you little.
SafetyKava carries the most serious safety flag of any common calming herb: dozens of reports of severe hepatotoxicity, including liver failure and transplant, led to bans or restrictions in Germany, Switzerland, France, Canada and the UK, several of which were later modified or reversed. Do not use with alcohol, paracetamol/acetaminophen, statins, methotrexate or any hepatotoxic drug, and avoid entirely with pre-existing liver disease. Kava causes clear driving and psychomotor impairment. Heavy chronic use produces kava dermopathy — a dry, scaly, yellowed rash. It inhibits several CYP enzymes (notably CYP2E1 and CYP1A2), so it can raise levels of co-administered drugs, and can worsen extrapyramidal symptoms in Parkinson's disease. Contraindicated in pregnancy, breastfeeding and depression. Baseline and periodic liver function testing is reasonable if used at all.

How to take it

TimingTake it in the evening, and only when you have no more driving or machinery for the day.
With food?Food makes no meaningful difference to effect, but reduces nausea.
Worth knowingInsist on noble-cultivar root, water-extracted - stems, leaves, peelings and solvent extracts account for most of the liver injury reports, and baseline liver tests are reasonable before starting.

Interactions

With medications

  • paracetamol/acetaminophen, statins, methotrexate and other hepatotoxic drugs

    Kava has caused liver failure on its own and the risk stacks. do not combine

  • alcohol, benzodiazepines and other CNS depressants

    Additive sedation with clear driving and psychomotor impairment. do not combine, and do not drive on kava at all

  • levodopa and Parkinson's medication

    Kava can worsen extrapyramidal symptoms and oppose dopaminergic treatment. do not use it if you have Parkinson's disease

  • narrow-therapeutic-index drugs metabolised by CYP2E1 or CYP1A2

    Kava inhibits both in humans and can raise drug levels. check with your pharmacist before combining

With other supplements

  • other sedating supplements such as valerian, magnolia and melatonin

    Additive sedation and impairment. do not stack them

  • green tea extract, gotu kola and other liver-risk supplements

    Additive hepatotoxicity risk. do not stack them

Well-established interactions only — this is not a complete list. Always tell your doctor and pharmacist what you take.

Frequently asked questions

Does kava work for anxiety?

The evidence is mixed: a Cochrane review of 12 trials found kava beat placebo by roughly 3.9 points on an anxiety scale, but the largest modern trial in 171 patients with generalised anxiety disorder found no difference from placebo. The overall case for kava is weaker than its popularity implies.

Is kava bad for your liver?

Kava carries a genuine, regulator-recognised liver risk: dozens of severe hepatotoxicity reports, including liver failure and transplant, led to bans or restrictions in several countries. Avoid kava with liver disease, alcohol, paracetamol, statins or methotrexate, and consider liver tests before starting.

How much kava is safe to take?

Kava trials used 120-280 mg of kavalactones per day, most commonly 240 mg/day, for 4-16 weeks. Choose water-extracted noble kava root, since stems, leaves, peelings and solvent extracts account for most liver injury reports.

Can you drive after taking kava?

No: kava causes clear driving and psychomotor impairment, and the effect adds to alcohol, benzodiazepines and other sedatives. Take kava only in the evening when you have no more driving to do.

Scientific references

Where to buy

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