Kava (Piper methysticum): Uses, Evidence and Safety

Safety first: liver injury, national restrictions and sedatives

Kava has been linked to rare cases of liver injury, some serious or fatal. NCCIH (part of NIH) says this in plain terms, and adds that some cases involved kava drinks made with water, not only products extracted with alcohol or acetone. [1] Memorial Sloan Kettering (MSK) goes further: it says the risk of liver damage outweighs any benefits. [2] Its warning signs are yellowing of the skin, eyes or nails, nausea and vomiting, and it says to contact a doctor right away if they appear. [2] A US FDA toxicology memo (2020) describes a World Health Organization review of 93 case reports of suspected kava liver harm, with 7 deaths and 14 liver transplants. [3] The same memo says the FDA warned consumers and doctors in 2002, and that kava has been withdrawn or banned in several countries. [3] The European Medicines Agency (EMA) committee for herbal medicines found the balance of benefit and risk unfavourable and decided that an EU herbal monograph cannot be established. [4] Kava should not be combined with alcohol or with sedating medicines. [1][2] Anyone with liver or kidney problems, who is pregnant or breastfeeding, who is taking medicines, or who has surgery planned should not use kava supplements without medical advice. See liver safety and supplements and supplements before surgery.

Overview

Kava is a drink or extract made from the root and rhizome (underground stem) of Piper methysticum G. Forst., a shrub in the pepper family (Piperaceae). [1][3] The FDA memo says it is native to Polynesia, Micronesia and Melanesia, and that the root is the part consumers ordinarily use. [3] NCCIH lists other names such as kava kava, awa and kawa. [1] The effects are linked to compounds called kavalactones. [2] This page covers kava root products: the traditional drink, powders, capsules and tablets, and extracts. Kava teas and tea-like drinks are signposted at kava, kratom and blue lotus teas. In the US, kava is sold as a dietary supplement, and in some other countries as a drug or herbal medicine. [1]

Traditional use (not proof of benefit)

Pacific Islanders have used kava drinks for thousands of years for ceremonies and for medicine, and kava bars now operate in many places, including US locations. [1] The FDA memo describes the traditional drink as macerated root mixed with cold water or coconut milk, drunk socially for its relaxing effect. [3] How long a plant has been drunk tells us about custom, not about whether it treats anxiety or is safe in a supplement. The findings below come from human trials and safety reports. For wider context see Kava in Specialty Topics.

What research shows

NCCIH says there has been a fair amount of human research on kava for anxiety, and little on other conditions. [1]

Whether the 2003 Cochrane result still holds for today's products: Proper evidence not found in the sources we read (the later 2020 trial was negative for diagnosed generalised anxiety disorder).

Forms and why the form matters

Kava products differ in how they are made. The FDA memo says commercial products have mostly been ethanol, methanol or acetone extracts standardised to kavalactone content, while the traditional drink is made with water. [3] The WHO review quoted in that memo noted a higher rate of liver reports with organic-solvent extracts. [3] But NCCIH says some liver cases involved water-prepared drinks, so a water extract is not proven safe. [1] NCCIH lists possible contributing factors, none settled: unsuitable varieties or plant parts, alcohol, adulteration or contamination, genetic differences, and large amounts or long use. [1] A result seen with one product should not be assumed for another. How much to use is a decision for a clinician, not this page.

Safety in more detail

• Liver: NCCIH reports rare serious or fatal liver injury. [1] MSK says risk is higher with prolonged use or with other botanicals, supplements or prescription medicines, and describes a case of acute liver failure needing a transplant after about two months of use without evidence of excess. [2] A 2019 case report describes liver failure and transplant in a woman after 52 days of a kava product at a standard dose; chemical testing found no contaminants. [7] The FDA memo adds that heavy kava drinkers often show raised liver blood tests. [3]
• Common side effects: NCCIH lists digestive upset, headache and dizziness. [1] MSK adds sedation, impaired reflexes or judgement, visual disturbances, restlessness, tremor and a "hangover" effect. [2] Do not drive or use heavy machinery after kava. [2]
• Skin: long-term heavy use can cause kava dermopathy (dry, scaly, flaky skin), reddened eyes and temporary yellowing of skin, hair and nails. [1][2]
• Medicines: do not combine with benzodiazepines, other sedatives or alcohol, which can add to drowsiness. [1][2] MSK also warns about acetaminophen (paracetamol), where lab studies suggested more liver toxicity, and about medicines processed by liver enzymes such as CYP1A2 and CYP2E1, while calling the overall interaction risk low. [2] Ask a pharmacist. See sedatives, sleep medicines and alcohol.
• Pregnancy: NCCIH says kava may carry special risks in pregnancy because of its pyrone compounds. [1] The FDA memo notes a lack of studies on reproductive and developmental harm. [3] MSK does not address pregnancy. [2] The sources we read give no reassurance, so avoid unless a doctor advises otherwise.
• Breastfeeding: NCCIH says the same caution applies. [1] Other details: Proper evidence not found in the sources we read.
• Children: Proper evidence not found in the sources we read.
• Liver and kidney disease: MSK advises people with liver or kidney problems to avoid kava. [2]
• Surgery: MSK advises stopping kava before surgery because it may interact with anaesthetics and add to sedation. [2] Tell the surgical team.
• Allergy: skin reactions with itching, burning or hives have been reported with kava tea or supplements. [2]
• Quality and contamination: NCCIH lists adulteration or contamination as a suggested contributor to liver cases. [1] The FDA memo says plant parts other than the root, other cultivars, or mould toxins may raise toxicity. [3] For label checks see quality testing and certifications.

Official statements

• EMA (EU), HMPC public statement, 21 November 2017: the benefit-risk balance is unfavourable; the committee noted spontaneous reports of liver reactions including liver failure, liver transplants and deaths, and withdrawal of products in some Member States, and also toxicology concerns (carcinogenic potential in animals). An EU herbal monograph cannot be established. [4]
• FDA (US), toxicology memorandum, 11 August 2020: the 2002 consumer advisory is described; the memo says kava is an unapproved food additive when used as an ingredient in conventional foods and that indiscriminate use as a relaxation drink is not safe. Kava supplements remain on sale in the US. [3]
• Countries with restrictions: the FDA memo lists withdrawals or bans in France, Switzerland, the Czech Republic, Spain, the UK, Hungary, Portugal and Germany (up to 2015), and Canada since 2002. It reports that in Australia kava is a Schedule 4 medicine with a limit on kavalactones from water-based extracts. [3] MSK says Canadian, French and British governments withdrew kava products. [2] These rules change; the current legal status in your country: Proper evidence not found in the sources we read, so check with your national regulator.
• NCCIH (US), page last updated April 2025: summary of the research and the liver warning above. [1]
• MSK, page last updated 9 February 2022: the liver risk outweighs any benefits. [2]

Related pages

• Kava in Specialty Topics
• Herbs and liver injury
• Herbs for anxiety and stress: what research shows
• Valerian
• Passionflower
• Sedatives, sleep medicines and alcohol with supplements