What Are the Side Effects of Kava?

Illustration of kava leaf and capsules

Many people these days are using kava for recreational and therapeutic benefit.

This useful herb has been shown time and time again to provide support anxiety and sleep disturbances. It’s a powerful herb with potent effects on the human body.

As with any powerful substance, there are going to be some risk of side-effects. Although many of the risks associated with kava have been blown way out of proportion (myths of causing liver failure), there are still some chances of unwanted side-effects.

In this article, we’ll explore the safety of kava in detail. We’ll cover what the science says about liver toxicity from kava use, the potential for addiction, drug interactions, potential side-effects, and when to avoid kava.

This is a huge topic. We’ve gone into great depth, so you can understand exactly what the risks are, and how you can minimize your chances of side-effects.

Let’s get straight into it by discussing how much kava is required to reach a toxic dose — you may be surprised.

Kava Dosage Limits: When Is Kava Dangerous?

The normal dosage of kava is around 10 – 50 grams of dried, powdered roots. 

Kava isn’t a dangerous herb. Most of the problems reported for this plant involved excessive doses, chronic long-term use, individual allergies to the plant, or combining the plant with other medications.

On its own, within the recommended safe dosage range of 140 – 300 mg kavalactones per day, kava hasn’t shown any indications of toxicity. One study on the safety of kava using 210 mg of kavalactones along with alcohol (a known liver toxin) didn’t find any damaging effects from the combination, despite previous warnings about liver toxicity [4].

Early reports of liver damage from a study in Switzerland lead to a nearly three-decade-long ban on the substance — despite plenty of research to dispute these findings.

One of the strongest indicators of kava’s safety is in its traditional uses. In some indigenous communities of the South Pacific, up to 80% of adult men and 20% of adult women consume high amounts of kava on a daily basis [5]. The dose these cultures often consume can be as much as 50 times the recommended doses used today.

Even with these high, repetitive doses, there’s little evidence the herb is dangerous. The majority of symptoms are mild in nature — like eczema, bloodshot eyes, or apathy. All of these symptoms are reported to disappear once kava consumption is ceased.

The best way to put a number on the toxicity of a substance is to look at the LD50 — the number that describes how much of a particular substance is needed to kill half the people (or animals) who consume it.

Here Are Some of the Oral LD50 Numbers for the Active Ingredients in Kava in a Mouse Model:

Dosage Equivalents   1. Demethoxyangonin (DMY) 2. Dihydrokavain (DHK) 3. Yangonin (Y) 4. Kavain (K) 5. Dihydromethysticin (DHM) 6. Methysticin (M)
Lethal Dose >800 mg/kg 920 mg/kg >1500 mg/kg 1130 mg/kg 1050 mg/kg (IP Injection) 530 mg/kg
Equivalent for Average Human (62 kg — 140 lbs) 49,600 mg 57,040 mg >93,000 mg 70,060 mg 65,100 mg 32,860 mg (injected)
Rough Equivalent in Grams of Powdered Kava >500 g >570 g >930 g >700 g >650 g >320 g

As you can see from the chart above, you’d need to consume more than 500 grams of kava powder to reach the lethal doses listed above. The average dose of kava is between 10 and 20 grams of powder per dose (depending on the strength of kava). You’d need to consume a dose over 30 times that of the normal dose to reach toxic levels.

For context, you use roughly 20 – 30 times as much water in mL as you do grams of kava. So for a normal 5-gram dose of kava, you would add 100 – 150 mL of water.

For a 500 mg dose, you’d need about 10 liters of water. The human stomach only holds about 2 – 4 liters worth.

Therefore, the only reasonable way of getting anywhere close to the lethal dose of kava is to inject pure kavalactones into the bloodstream.

The Lethal Dose of Oral Kava is Virtually Unreachable, But is Kava Still Dangerous?

Although it’s virtually impossible to reach the lethal dose of kava without injecting the kavalactones directly into the bloodstream. There are some negative reactions that are still a possibility.

We’ll cover each of the following in more detail below:

  1. Kava may be dangerous to the liver if consumed alongside alcohol or other known liver toxins
  2. Excessive kava use can lead to a form of eczema known as kava dermopathy
  3. The anti-anxiety effects of kava can become addictive over time — though much less addictive than conventional anti-anxiety medications
  4. High doses of kava can increase the chances of accidents due to the sedative effect

Common Side Effects of Kava

Kava is a powerful herb, so it’s not surprising there are some potential side-effects. Most of them are very mild and subside once the effects of the kava wear off. If you experience mild side-effects after a dose of kava, try taking a smaller dose the next time. This is usually enough to keep the side-effects of kava at bay.

The exception here is allergies. If you experience any allergies to kava, avoid it altogether.

Mild Side-Effects of Kava Include:

  • Dilated pupils
  • Fatigue
  • Headaches
  • Indigestion
  • Lightheadedness
  • Facial puffiness
  • Visual disturbances

More Severe Side-Effects of Kava Include

  • Enlarged liver
  • Increased red blood cell count
  • Kava dermopathy (scaly skin)
  • Lowered serum protein (less protein in the blood)
  • Lymphocytopenia (low lymphocyte levels)
  • Pulmonary hypertension
  • Thrombocytopenia (lower blood plasma levels)

These severe side-effects are much less common and rarely appear after just one dose of kava. Instead, these symptoms tend to appear gradually along with consistent high doses of kava.

To avoid these symptoms, avoid taking high doses of kava on a daily basis. It’s wise to take periodic breaks from any health supplement. You can choose to take a week off each month or every fourth day, for example.

Kava Headaches

Some people get headaches after drinking a lot of kava. These headaches are usually described as a dull, low-grade headache affecting the bottom-back of the head just above the neck. Some people experience the headache more along the top of the head instead. 

The potential causes for kava headaches include: 

  • Dehydration (most common)
  • High concentrations of DHK or DHM
  • Dependency (headache starts when kava wears off)
  • Fatigue

The most common cause of headaches from kava is dehydration. This is especially common when using kava capsules, tinctures, or concentrates. When kavalactones enter the bloodstream, the kidneys ramp up activity to filter them out. The same happens when we take any supplements, which is what makes herbs like kava, coffee, or tea a diuretic (makes you pee). When we’re filtering more fluid from the blood, it needs to be replaced by drinking water. If it isn’t replaced, we become dehydrated, which causes a headache. 

Other potential causes for headaches are certain kavalactones directly — such as DHM or DHK. While it’s not clear how these compounds cause headaches, some strains that are especially high in these compounds are noted to have the highest chances of causing a headache. 

Some people may even experience headaches when they’re tired. Kava is a sedative, especially in higher doses, so it’s possible for kava headaches to be the result of fatigue and tiredness as well. 

Kava could theoretically also cause headaches when it wears off — but only in people who use the herb on a very regular basis. This happens in a similar way to benzodiazepine medications, which share the same mechanism of action. The body learns to depend on the kavalactones to maintain GABA balance in the brain. When we stop taking the herb after using it for a long time, GABA levels may decrease temporarily, resulting in a dull, low-grade headache. 

The best way to avoid headaches when using kava is to drink water in between doses — even if you’re drinking traditional kava tea. 

Kava & Liver Toxicity

Kava has been proven safe time and time again through both animal and human studies, yet some countries continue to ban the sale and use of kava supplements under the pretense that the herb can be toxic to the liver.

There have been cases of liver toxicity reported in people using kava — but it’s important to note that these subjects were also taking other compounds with known liver toxicity. The conditions in which these injuries were reported have been challenged by medical authorities.

It seems kava doesn’t reliably produce any signs of liver damage on its own — but can amplify the negative effects of other compounds when taken in combination.

However, large doses of kava (well outside the recommended dosage range) have been shown to have some damaging effects on the liver. These doses were in the realm of more than 60 grams of kava root per day — 10 times the recommended dose.

Let’s explore exactly how kava could cause damage to the liver based on its physiological effects on the body.

There are three possible ways kava may negatively affect the liver [1]:

  1. Inhibition of cytochrome P450 (liver enzymes responsible for metabolism)
  2. Reduction of liver glutathione (a protective antioxidant found in the liver)
  3. Inhibition of cyclooxygenase (COX) (an enzyme responsible for producing chemical messengers)

The risk to benefit ratio of kava is very good, especially compared to other medications used to treat symptoms like insomnia or anxiety. The most common class of drug used to treat these symptoms are the benzodiazepines — which have also been found to come with the risk of liver-toxic effects [2], as well as a long list of other negative side-effects, including memory loss, addiction, and confusion.

The bottom line is that kava is unlikely to cause any liver damage in recommended doses — but it’s not impossible. In order to minimize the risk, you should avoid using kava alongside other substances that can harm the liver — including statin medications, alcohol, Tylenol, aspirin, Amoxicillin, Diclofenac, anti-seizure medications, Azathioprine, and more.

Consult with your doctor before taking kava if you’re using other medications or have any drug addictions.

If you remain within the recommended dosage range for kava, take regular breaks off of kava, and avoid using the herb if taking medications with known liver toxicity or underlying liver conditions — it’s very unlikely you’ll sustain any damage to your liver.

Signs of Liver Damage

Let’s briefly discuss how liver damage presents. If you experience any of these symptoms, make sure to visit a doctor immediately. Although extremely rare, liver damage is a serious illness.

  • Yellowing eyes and skin (jaundice)
  • Dark urine color
  • Itchy skin
  • Extreme abdominal pain and nausea
  • Swelling in the ankles and lower leg
  • Abdominal swelling (Ascites)

Kava Dermopathy

One of the characteristic side-effects of kava — especially in very large doses over long periods of time — is a particular skin lesion formation called kava dermopathy. These skin patches have a dry scaly appearance on the surface layers of skin.

This condition is well-known among kava drinkers, and most of the Pacific islands with a long history of kava use report this effect. In Fiji, the condition is referred to as kani kani. Another common name for the condition is crocodile skin — due to the scaly appearance of the skin lesion which can form on the limbs or abdomen.

Some of the early researchers of kava use among indigenous cultures of the South Pacific would search for these patches of eczema along with bloodshot eyes to find people who used particularly high doses of kava.

Kani kani doesn’t form after a single-use. Most commonly, the condition will form slowly over time with long-term high-dose kava consumption (over 310 grams of dried kava per week).

It only affects people with a mild allergy to kava — which becomes more severe over time. The kavalactones in the herb have a chemical group that allows them to attach themselves to proteins in the skin — triggering an allergic reaction in susceptible individuals [3].

This side-effect isn’t serious and will gradually disappear if you stop drinking kava for a while or reduce the dose.

Is Kava Addictive?

Kava is a powerful plant — it’s been shown through multiple clinical trials [6,7], including a Cochrane review (the best form of clinical research available) to be effective for symptoms of anxiety. Some of this research even suggested that it may be a reasonable alternative to benzodiazepines — one of the key medications used in the treatment of anxiety.

Addiction to anti-anxiety drugs is very common. There are two perfectly good explanations for addiction to anxiety medications — one physical, one psychological — which we’ll cover in detail below. Kava is significantly less addictive than other anti-anxiety medications such as Xanax or Klonopin, but it isn’t an exception to these causes of addiction.

So what makes anti-anxiety meds addictive?

1. Psychological Addiction (Habit Formation)

Imagine living with anxiety. Social environments are almost unbearable leading you to become a recluse. Or perhaps your fear of speaking in public may be holding back your success at work. Maybe you’re finding it hard to form new relationships because of your fear of opening up to people, avoiding vulnerability and intimacy altogether. Maybe you simply can’t get a good night’s sleep.

Anxiety affects everybody’s lives differently — but it’s never pleasant.

Now imagine you found something that removes this anxiety — whether it’s a benzo like Xanax or an herb like kava. Even if just for a little while, this treatment becomes very attractive. This is the main reason people continue to use these meds over long periods of time. Because they work, and anxiety sucks.

Addiction to anxiety meds starts out slowly, often going unnoticed for weeks or months. Users will start out by taking the medications only when they need them at first but will start to rely on them more and more over time. Eventually, they’ll reach a point where they think the medications (or in this case kava) is the only thing keeping them from having constant anxiety attacks.

This is when the next form of addiction may begin — physical addiction — which is much more severe.

Fortunately, kava is significantly less addictive than pharmaceutical anti-anxiety medications such as benzodiazepines or barbiturates — but it can still become habit forming over time.

The best way to avoid this issue is to take breaks from kava from time to time.

Many people will use kava for 3 weeks, and take 1 week off. Or 3 days on, one off. This can go a long way in preventing habit formation of kava or any herb or supplement.

2. Physical Addiction (Tolerance Formation)

Physical addiction forms once you’ve used an addictive substance steadily for a few weeks or months. Some substances are much more addictive than others.

Opiates, for example, are highly addictive — forming physical addiction after just a few days.

What is physical addiction? How does it work?

Chemical compounds used as medicine will usually target a specific receptor to exert its effects — in the case of anti-anxiety medications, this usually means the GABA receptors.

The chemical will cause a change to the receptor, which results in the effect — in this case, a reduction of certain brain activity and anxiety.

In the short term, these chemicals work great and can have powerful effects on the body. But over time, the body will adapt to these chemicals and make changes to the receptors in order to counteract them.

(Xanax — a Common Benzodiazepine Medication)

In the case of benzodiazepines, the body will form a tolerance by hidingGABA receptors. When this happens, we need to take more of the drug in order to achieve the same effect. This process is referred to as tolerance because the body begins to tolerate the drug.

As this process continues to progress we get another problem.

When the receptors change too much, to account for the presence of a chemical like a benzodiazepine in the bloodstream, we become reliant on it in order to maintain balance. As soon as the drug wears off, the body is out of balance. There are now too few GABA receptors to maintain balance — causing us to experience the very symptoms we aimed to treat — anxiety.

This process of falling out of control once the drug wears off is called withdrawal. This is the hallmark of physical addiction and is the reason why people who are addicted to drugs can’t stop taking them.

As soon as they do, they experience symptoms much worse than before they ever started the medication. In the case of severe benzodiazepine addiction, withdrawal symptoms can be so severe they can actually lead to cardiac failure and death.

What does this mean for kava users?

In theory, kava is addictive because it works through the same receptors as well-known addictive drugs like benzodiazepines.

In practice, kava simply doesn’t have the same potential for addiction.

One of the leading theories as to why kava lacks this addictive quality for most people is that although it works through GABA, it’s not exclusive to this receptor-like conventional anxiety medications. This may explain why kava has such a low incidence of physical addiction.

Recent research explored the addictive potential of kava in more detail. They gave study participants either 120 mg worth of kavalactones, 240 mg of kavalactones, or a placebo for 8 weeks. At the end of the study, researchers noted no relevant difference in tolerance-formation or cravings for more capsules (indicators of addictive qualities). Researchers also noted no indications of withdrawal symptoms in any of the study participants [8].

In fact, one preliminary study even suggested that kava may be a useful agent for curbing the cravings of other addictive substances such as alcohol, tobacco, cocaine, and heroin [9].

Defining Kava Abuse

Many people enjoy kava regularly and can do so safely. But it is possible to enjoy kava too often, so it’s useful to quantify when kava consumption becomes too much.

The best way to measure kava use over time is to measure the amount of kava you consume on a weekly basis. This is because individual doses can vary, which can give unreliable numbers.

Some people consume smaller doses of kava but will take several doses each day. Others may only take kava once or twice per day, but consume much higher doses.

Defining Kava Consumption Patterns By Week

  1. Occasional kava drinker — less than 100 grams of root powder per week (10 – 15 grams of kavalactone resin). This dosage rarely results in any chronic side-effects of kava. You should always try to stay within this category of kava consumption.
  2. Heavy kava drinkers — up to 310 grams of kava root powder per week (30 – 45 grams of kavalactone resin). These users may experience negative side-effects after a few weeks though, many don’t. This is the first sign of potential addiction to the effects of kava.
  3. Very heavy kava drinkers — 440 grams of dried kava powder per week (40 – 70 grams of kavalactone resin). These users are the most likely to experience side-effects from kava. If you find you’re within this category of kava user, you should strongly consider taking some time off kava to avoid any tolerance and addiction to the herb.

Final Tips on Staying Safe While Using Kava

No therapeutic agent comes completely risk-free. If a compound (or herb) exerts changes on the body, there will always be some potential for side-effects.

Kava is no different.

This powerful herb has a lot of potential as a therapeutic agent, and in higher doses, can even cause an enjoyable euphoric sensation. The risk of side-effects with an herb this strong is always possible, but with care and responsible consumption, these side-effects can be kept to a minimum — or even avoided altogether. It’s important to note here that the risk imposed by kava is significantly lower than comparable medications such as barbiturates or benzodiazepines.

The most common side-effects of kava are sedation, indigestion, and lightheadedness. These symptoms disappear once the kava wears off. More severe side-effects are possible but are extremely rare and tend to only affect people using high doses of the herb over long periods of time.

Most experts agree that kava only poses danger if taken alongside compounds with known toxic effects on the liver, in people with liver or kidney disorders, or when taken in high doses for long periods of time.

How to stay safe while using kava:

  • Speak with a doctor to make sure it won’t interfere with any underlying health conditions or medications
  • Only buy kava from a reputable dealer
  • Start with a low dose of the herb to see how it affects your body individually

Using kava responsibly can be a very safe and enjoyable experience. Learn more about how to use kava by reading through our quick reference kava user guide, and check out our kava buyer’s guides to find which types of kava may be best for you.

Sources Cited in This Article

  1. Clouatre, D. L. (2004). Kava kava: examining new reports of toxicity. Toxicology Letters, 150(1), 85-96.
  2. Zimmerman, H. J. (1999). Anticonvulsants. In, Zimmerman, HJ. Hepatotoxicity: the adverse effects of drugs and other chemicals on the liver.
  3. Hannam, S., Murray, M., Romani, L., Tuicakau, M., & J Whitfeld, M. (2014). Kava dermopathy in Fiji: an acquired ichthyosis?. International journal of dermatology, 53(12), 1490-1494.
  4. Herberg, K. W. (1993). Effect of Kava-Special Extract WS 1490 combined with ethyl alcohol on safety-relevant performance parameters. Blutalkohol, 30(2), 96-105.
  5. Lebot, V., Merlin, M., & Lindstrom, L. (1997). Kava: The Pacific Elixir: The definitive guide to its ethnobotany, history, and chemistry. Inner Traditions/Bear & Co.
  6. Volz, H. P., & Kieser, M. (1997). Kava-kava extract WS 1490 versus placebo in anxiety disorders-a randomized placebo-controlled 25-week outpatient trial. Pharmacopsychiatry, 30(01), 1-5.
  7. Warnecke, G. (1991). Psychosomatic dysfunctions in the female climacteric. Clinical effectiveness and tolerance of Kava Extract WS 1490. Fortschritte der Medizin, 109(4), 119-122.
  8. Sarris, J., Stough, C., Teschke, R., Wahid, Z. T., Bousman, C. A., Murray, G., … & Schweitzer, I. (2013). Kava for the treatment of generalized anxiety disorder RCT: analysis of adverse reactions, liver function, addiction, and sexual effects. Phytotherapy Research, 27(11), 1723-1728.
  9. Steiner, G. G. (2001). Kava as an anti-craving agent: preliminary data. Pacific health dialog, 8(2), 335-339.