Kanna Side Effects, Safety and How to Take It

Kanna (Sceletium tortuosum) is a South African succulent that people have chewed for centuries to feel calmer and more sociable. Today it is sold as capsules, powders, tinctures and nasal sprays. This guide covers what the human studies found about kanna side effects and safety, which medicines it should not be mixed with, and how to take kanna in each form, including dose and timing.

It is educational, not medical advice.

Key Takeaways

• Kanna was well tolerated in human trials. In a 3-month trial of 37 healthy adults, daily kanna extract caused no changes in vital signs, heart tracings or blood tests, and side effects were no more common than with placebo.
• What the research covers. Studies used standardized extracts at 8 to 25 mg a day in healthy volunteers, for a single dose up to 3 months.
• Do not mix kanna with medicines that affect serotonin, such as SSRIs, SNRIs or MAOIs, unless your clinician agrees. Kanna blocks serotonin reuptake in lab studies, so the effects could add up.
• Commonly reported side effects are mild: headache, an upset stomach, and feeling drowsy or “flat” at higher amounts.
• Start low. Potency varies widely between products, so start with the lowest strength and change one thing at a time.

What Kanna Is and How It Works

Kanna’s main active compounds are alkaloids, chiefly mesembrine. In lab studies, a standardized kanna extract blocks the reuptake of serotonin and inhibits an enzyme called PDE4, which helps regulate signaling inside brain cells (Terburg et al., 2013). The serotonin action is the main reason for the safety cautions below. For the background, see what is kanna and our kanna ingredient page.

Is Kanna Safe? What Human Studies Found

The published human trials used standardized extracts, in healthy volunteers:

• 3-month safety trial. 37 healthy adults took 8 mg or 25 mg a day, or a placebo. There were no differences in vital signs, heart tracings (ECG), body weight or physical exams, and no significant changes in blood tests. The most common side effects were headache, abdominal pain and colds, all more frequent in the placebo group (Nell et al., 2013).
• 3-week thinking study. 21 healthy adults averaging 55 years took 25 mg a day. It was well tolerated, and scores for mental flexibility and executive function improved compared with placebo (Chiu et al., 2014).
• Single-dose stress studies. In 20 young adults, one 25 mg dose lowered self-rated tension before a public speaking task (Reay et al., 2020). In 16 adults, one 25 mg dose calmed the brain’s response to threatening faces on a brain scan (Terburg et al., 2013).
• 8 days in active adults. 25 mg a day improved performance on complex reaction tasks under mental load (Hoffman et al., 2020).

A 2026 review of all the animal and human studies described the safety record as good (de Jong et al., 2026). Results from standardized extracts may not apply to raw powders or other extracts, which can be much stronger or weaker.

Kanna Side Effects

In the trials, side effects were mild and no more common than with placebo. People who use kanna most often report:

• Headache.
• Upset stomach or nausea, more often with raw powder or larger oral amounts.
• Drowsiness or feeling “flat”, usually a sign the amount is too high.
• With a nasal spray: brief stinging, a runny nose or a bitter taste at the back of the throat.

If a side effect is strong or does not settle, stop and talk with a healthcare provider.

Kanna Drug Interactions

Because kanna blocks serotonin reuptake in lab studies, combining it with other things that raise serotonin could add up. The safe approach is to avoid combining kanna with these unless your clinician agrees:

• Prescription medicines that affect serotonin, including SSRIs, SNRIs, MAOIs and tricyclics.
• Other serotonin-raising products, such as triptans, tramadol, St. John’s wort and 5-HTP.
• Alcohol and sedatives, which can add to drowsiness.
• Several kanna products at once. Pick one form and one strength.

Kanna is sometimes confused with kava, a different plant with its own safety profile; see kanna vs kava for how they compare. It is also confused with kratom, and our guide to how kanna and kratom differ compares their effects, safety and legal status.

Liver, Blood Pressure and Dependence

Is kanna safe for your liver?

In the 3-month trial, routine blood chemistry did not change significantly with daily kanna (Nell et al., 2013), and no liver problems have been reported in the published human studies. That trial ran for 3 months, so talk with a provider first if you have a medical condition or take medication.

Does kanna raise blood pressure?

Vital signs did not differ from placebo over 3 months of daily use in the same trial. If you monitor your blood pressure for any reason, check with your provider before starting.

Is kanna addictive?

No study has reported dependence or withdrawal. Use it at the labeled amount and avoid mixing it with alcohol.

Who Should Not Take Kanna

• People who are pregnant or breastfeeding.
• Anyone under 18.
• Anyone taking the medicines listed above without their clinician’s agreement.
• Anyone with a medical condition who has not checked with a healthcare provider.

Do not drive or operate machinery until you know how kanna affects you.

How to Take Kanna

Form	How it is used	What to know
Capsules or tablets	Swallowed with water	The form used in the human studies (8 to 25 mg of a standardized extract a day); check the label for extract strength
Powder	Chewed, held in the mouth or mixed into a drink	Strength varies widely; raw plant powder is much weaker per gram than an extract
Tea or tincture	Steeped or taken in drops	Hard to measure a consistent amount
Under the tongue	Lozenges, tablets or powder held under the tongue	Absorbed partly through the mouth, so less of each dose passes through digestion than with capsules
Nasal spray	One spray in each nostril	Absorbed through the lining of the nose instead of being swallowed like a capsule, so some of each dose skips digestion; faster onset than capsules

For help choosing a product, see our best kanna supplement guide and kanna nasal spray vs oral kanna.

How much kanna to take

The human studies used 8 to 25 mg a day of a standardized extract. Products differ in extract ratio and alkaloid content, so milligrams on one label do not match another. Start with the lowest amount or strength, stay there for several days, and only then consider moving up.

Morning or evening?

No study has compared times of day. Most people use kanna during the day for calm focus or before social situations. If it makes you drowsy, move it to the evening.

How long does kanna take to kick in, and how long does it last?

Published kanna studies have looked at mood, stress, thinking and safety markers rather than how long it stays in your system. A nasal spray is designed for a faster onset, within minutes. For timing and how long a nasal spray serving lasts, see our how to use kanna nasal spray guide.

How to Take Kanna Nasal Spray

Our Kanna Nasal Spray comes in three strengths: 20 mg, 35 mg or 50 mg of kanna extract per two-spray serving, with 15, 25 or 35 mg of L-theanine, in alkaline water. One serving is one spray in each nostril, and each bottle holds 30 servings. To adjust how strong it feels, change the strength rather than the number of sprays, and start with Regular Strength.

• Breathe in gently while you spray; if it reaches your throat, inhale more softly next time.
• Tilt your head back slightly and wait at least 60 seconds before blowing your nose.
• It can be taken with or without a meal.

Step-by-step tips are in our kanna nasal spray guide, and more answers are on the Kanna Nasal Spray FAQ.

Sources

• Terburg D et al. Acute effects of Sceletium tortuosum (Zembrin), a dual 5-HT reuptake and PDE4 inhibitor, in the human amygdala and its connection to the hypothalamus. Neuropsychopharmacology, 2013. PubMed
• Nell H et al. A randomized, double-blind, parallel-group, placebo-controlled trial of Extract Sceletium tortuosum (Zembrin) in healthy adults. J Altern Complement Med, 2013. PubMed
• Chiu S et al. Proof-of-Concept Randomized Controlled Study of Cognition Effects of the Proprietary Extract Sceletium tortuosum (Zembrin) Targeting Phosphodiesterase-4 in Cognitively Healthy Subjects: Implications for Alzheimer's Dementia. Evid Based Complement Alternat Med, 2014. PubMed
• Reay J et al. Sceletium tortuosum (Zembrin(®) ) ameliorates experimentally induced anxiety in healthy volunteers. Hum Psychopharmacol, 2020. PubMed
• Hoffman JR et al. Ergogenic Effects of 8 Days of Sceletium Tortuosum Supplementation on Mood, Visual Tracking, and Reaction in Recreationally Trained Men and Women. J Strength Cond Res, 2020. PubMed
• de Jong M et al. Mesembryanthemum tortuosum and Zembrin: Mixed Evidence from In vivo Animal and Clinical Studies on their Antidepressant and Anxiolytic Effects. Planta Med, 2026. PubMed

Frequently Asked Questions

Is kanna safe?

In human trials, a standardized kanna extract at 8 to 25 mg a day was well tolerated for up to 3 months, with no changes in vital signs, heart tracings or blood tests. The studies were small and in healthy adults, and kanna should not be combined with medicines that affect serotonin.

What are the side effects of kanna?

The most commonly reported are headache, an upset stomach and feeling drowsy or flat at higher amounts. Nasal sprays can cause brief stinging or a runny nose. In trials, side effects were no more common than with placebo.

Can you take kanna with SSRIs?

Not without your clinician’s agreement. Kanna blocks serotonin reuptake in lab studies, so combining it with SSRIs, SNRIs, MAOIs or other serotonin-raising products could add to their effects.

Is kanna safe for your liver?

Blood chemistry did not change significantly over 3 months of daily use in a controlled trial, and no liver problems have been reported in published human studies. That trial ran for 3 months.

Does kanna raise blood pressure?

Vital signs did not differ from placebo over 3 months of daily use in a controlled trial. Check with your provider if you monitor your blood pressure.

Is kanna addictive?

No study has reported dependence or withdrawal.

How long does kanna last?

Published kanna studies have looked at mood, stress, thinking and safety markers rather than how long a dose lasts. Follow the label serving.

How long does kanna take to kick in?

A nasal spray is designed for a faster onset, within minutes. Capsules are swallowed and pass through digestion first.

Should I take kanna in the morning or evening?

There is no research on timing. Most people take it during the day; if it makes you drowsy, take it in the evening instead.

What is the best way to take kanna?

The one you can dose consistently. Capsules match what the studies used, while a nasal spray offers a measured serving with a faster onset. Start with the lowest strength either way.

These statements have not been evaluated by the Food and Drug Administration. This content is for education and is not medical advice. Our products are not intended to diagnose, treat, cure or prevent any disease. Do not use kanna if you are pregnant, breastfeeding, under 18, or taking medication that affects serotonin, unless your healthcare provider agrees.