Is Kanna Safe? Side Effects, Interactions and Who Should Skip It
Short human trials look well tolerated in healthy adults, but the data are small, and anyone on serotonin-affecting medicine should talk to a doctor first.
Is kanna safe? For healthy adults, the short answer from the limited research is "probably well tolerated at the doses studied, with big caveats." The studies are small, mostly short, and mostly of one branded extract. And for anyone taking antidepressants or other serotonin-affecting medicine, "ask your doctor first" is the right answer. This page lays out what the data show, what they do not, and who should sit this one out.
In small trials of one standardized kanna extract (Zembrin), healthy adults tolerated 8 mg and 25 mg daily for 3 months with no vital-sign, ECG or bloodwork differences from placebo [1]. Reported side effects are mild, mainly headache and upset stomach [5]. Interactions with SSRIs and similar drugs are not fully understood, so check with a doctor first [5].
What do safety studies show?
The best human safety data come from a handful of small trials, nearly all using Zembrin, a standardized Sceletium tortuosum extract. They are encouraging, but they are not proof of long-term safety.
The most direct one is a 2013 study by Nell and colleagues. It was randomized, double-blind and placebo-controlled, with 37 healthy adults taking 8 mg or 25 mg of Zembrin once daily, or placebo, for 3 months. Vital signs, physical exams, ECGs, blood tests and urinalysis showed no apparent differences between groups. The authors concluded both doses were well tolerated [1]. Efficacy was not tested; the trial was built only to look at safety.
A 2014 toxicology paper tested the same extract in rats. In a 14-day study at up to 5,000 mg/kg per day and a 90-day study at up to 600 mg/kg per day, researchers saw no mortality or treatment-related adverse effects. Those highest doses were set as the no-observed-adverse-effect levels [2]. Rat data do not translate directly to people, but they are a standard part of how food and supplement ingredients get evaluated.
Other trials add small pieces. In a 2014 crossover study of 21 healthy adults (average age about 55) taking 25 mg a day for 3 weeks, the extract was reported as well tolerated [3]. A 2020 pair of studies in 20 young healthy volunteers used a single 25 mg dose [4].
A 2026 critical review of animal and clinical work described a "favourable safety profile" alongside mixed evidence on effects and limits such as small sample sizes [7].
Limits worth knowing
- Small and short. The longest trial we found was 3 months with 37 people [1].
- Healthy volunteers. A 2021 review notes the plant has not yet been studied in a clinical population [8]. Results may not apply to people with health conditions or on medication.
- One extract. The trials used Zembrin. A different extract at the same milligram number is not the same thing.
- Industry ties. At least one of these papers lists authors from the company that owns Zembrin [2], so read the safety findings as industry-linked.
What are the side effects of kanna?
WebMD lists headache and upset stomach as the common side effects of sceletium [5]. It also advises stopping use and getting help for signs of a serious allergic reaction [5].
The trial data are consistent with mild effects. In the 3-month study, headache was the most commonly reported adverse event, followed by abdominal pain and upper respiratory infections, and all of these were more common in the placebo group than in the kanna groups [1]. That does not mean kanna prevents headaches. It means that in a small trial, these complaints showed up regardless of what people took.
Because the evidence base is thin, rarer or longer-term effects could exist that no study was large enough to catch. If something feels off after a kanna product, stop and talk to a clinician.
Why do SSRIs and other medicines matter?
They matter because of serotonin syndrome, a reaction that happens when too much serotonin builds up in the body, usually from combining substances that each affect serotonin.
MedlinePlus, from the National Library of Medicine, describes serotonin syndrome as a potentially life-threatening reaction to certain medicines that can be fatal if untreated. It usually happens when two or more serotonin-affecting substances are taken together, and the risk is higher when a medicine is first started or the dose is raised. The drugs it names include SSRIs, SNRIs, MAOIs and triptans (migraine medicines) [6]. Symptoms can begin within minutes to hours and include agitation or restlessness, fast heartbeat, high blood pressure, diarrhea, overactive reflexes, loss of coordination and a rise in body temperature [6].
Where does kanna come in? In a lab study, a standardized kanna extract blocked the serotonin transporter, the same protein that SSRIs are designed to act on, and it also inhibited an enzyme called PDE4 [10]. That is a test-tube finding, not a measurement of what happens in a person who takes kanna alongside a prescription. WebMD says the interactions between sceletium and medicines "are not fully understood" and lists concerns with MAOIs, SSRIs, SNRIs, tricyclic antidepressants, antipsychotics, triptans and St. John's wort [5].
So nobody can tell you the exact risk, which is precisely why the advice is conservative. Some kanna drink makers say the same on their labels. Kanva Botanicals, for example, warns against use with SSRIs and SNRIs on its product page [11].
| Medicine or supplement type | Examples | Why it is flagged |
|---|---|---|
| SSRIs | sertraline, fluoxetine, escitalopram | Named by MedlinePlus as a cause of serotonin syndrome [6]; listed by WebMD for kanna [5] |
| SNRIs | venlafaxine, duloxetine | Same [5][6] |
| MAOIs | older antidepressants | Same [5][6] |
| Tricyclic antidepressants | older antidepressant class | Listed by WebMD [5] |
| Triptans | sumatriptan, rizatriptan | Migraine medicines; named by both [5][6] |
| St. John's wort | herbal supplement | Listed by WebMD [5] |
Drug-name examples come from the MedlinePlus lists [6]. The list is not complete. If you take any prescription medicine, ask your pharmacist.
One practical point: do not stop or change a prescribed medicine on your own to try kanna. MedlinePlus advises talking to your provider before stopping a prescribed medicine [6].
Who should skip kanna?
People who take any of the medicines in the table above, who are pregnant or breastfeeding, or who are under the legal age for the product should skip kanna, or at minimum talk to a doctor first.
- Anyone on serotonin-affecting medicine. SSRIs, SNRIs, MAOIs, tricyclics, triptans and St. John's wort, as above [5].
- Pregnant or nursing people. WebMD says it is not known whether sceletium could affect pregnancy or harm a fetus, or whether it passes into breast milk [5]. Unknown is not the same as safe.
- Younger people. We found no safety studies in children or teens; the trials above enrolled adults [1][3][4]. Brands set their own age limits (Upstate Elevator, for example, states 18+), and we would use 21+ as the cautious line for a drink aimed at adults.
- People with health conditions or several medicines. Trials excluded this group in practice, since they enrolled healthy volunteers [8]. A pharmacist can check for interactions in a few minutes.
Do product quality and dose vary?
Yes, a lot. The plant's chemistry changes with growing conditions, harvest timing and processing, and WebMD notes that switching brands may not give you the same effects or side effects [5].
WebMD also says the FDA has not tested sceletium products to confirm they contain what the label says, and that some sceletium supplements have been found to contain other ingredients, such as ephedrine [5]. The FDA does not approve dietary supplements for safety and effectiveness before they sell, and manufacturers are responsible for making sure products meet safety standards [9].
For drinks, the practical issue is dose. Trials used 8 to 50 mg of a standardized extract. On the market, we found cans listing anywhere from 15 mg to 500 mg of kanna, with different extract types, and some brands do not state the amount on their product pages. Those numbers are not comparable unless the extract is standardized the same way. Our ranking of kanna drinks lists what each label states. For how studies chose their doses, see kanna dosage.
Look for a brand that states milligrams, names the extract, and prints a clear interaction warning. Silly, for example, lists 35 mg of kanna per can without stating extract standardization on the label, so we flag that gap ourselves; see how it ranks.
Can you mix kanna with alcohol?
There is no research showing it is safe, so the cautious answer is no. WebMD says there is not enough research to know whether sceletium interacts with foods or drinks, including alcohol [5].
Many people reach for kanna drinks as alcohol alternatives, which is a different thing from mixing the two. If you are drinking alcohol, adding a psychoactive plant extract on top adds unknowns to a situation that already impairs judgment and coordination. That is our editorial caution, not a finding from a study.
So, is kanna safe?
For most healthy adults, the limited evidence points to good short-term tolerability at studied doses, mainly with mild effects like headache and upset stomach. The honest summary has three parts.
- The human safety data are small, short and tied to one extract.
- Serotonin-affecting medicines are the clearest reason to avoid it or ask a doctor first.
- Pregnancy, nursing, alcohol and long-term use are unknowns, and unknowns call for caution.
If you want to read more about what the research does and does not show for effects, see what the research says and what kanna is. This page is general information, not medical advice. These statements have not been evaluated by the FDA, and kanna products are not intended for any disease or health condition.
References
- Nell H, Siebert M, Chellan P, Gericke N. A randomized, double-blind, parallel-group, placebo-controlled trial of Extract Sceletium tortuosum (Zembrin) in healthy adults. J Altern Complement Med 2013;19(11):898-904. PubMed
- Murbach TS, Hirka G, Szakonyine IP, Gericke N, Endres JR. A toxicological safety assessment of a standardized extract of Sceletium tortuosum (Zembrin) in rats. Food Chem Toxicol 2014;74:190-9. 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. Evid Based Complement Alternat Med 2014;2014:682014. PubMed
- Reay J, et al. Sceletium tortuosum (Zembrin) ameliorates experimentally induced anxiety in healthy volunteers. Hum Psychopharmacol 2020;35(6):1-7. PubMed
- WebMD. Sceletium: Uses, side effects, interactions. webmd.com
- MedlinePlus. Serotonin syndrome. National Library of Medicine. medlineplus.gov
- 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;92(8):806-823. PubMed
- Olatunji TL, et al. Sceletium tortuosum: a review on its phytochemistry, pharmacokinetics, biological and clinical activities. J Ethnopharmacol 2021;280:114476. PubMed
- U.S. Food and Drug Administration. FDA 101: Dietary supplements. fda.gov
- Harvey AL, et al. Pharmacological actions of the South African medicinal and functional food plant Sceletium tortuosum and its principal alkaloids. J Ethnopharmacol 2011;137(3):1124-9. PubMed
- Kanva Botanicals. Release + Relax product page (label and warning). kanvabotanicals.com
Frequently asked questions
Is kanna safe to drink every day?
The longest human safety trial we found ran 3 months at 8 mg or 25 mg a day of one standardized extract in 37 healthy adults, and found no differences in vital signs, ECG or bloodwork versus placebo [1]. There are no long-term studies beyond that, and other products may differ.
What are the side effects of kanna?
WebMD lists headache and upset stomach as the common side effects [5]. In the 3-month trial, headache was the most commonly reported adverse event, and it was more common in the placebo group [1].
Can I take kanna with an SSRI?
Not without talking to your doctor or pharmacist. WebMD lists SSRIs, SNRIs, MAOIs, tricyclics, triptans and St. John's wort as medicines of concern, and says the interactions are not fully understood [5]. See why serotonin matters.
Is kanna safe during pregnancy or breastfeeding?
Nobody knows. WebMD states it is not known whether sceletium could affect pregnancy or harm a fetus, or whether it passes into breast milk [5]. Skip it unless your doctor says otherwise.
Has the approved by the FDA kanna?
No. The FDA has not reviewed sceletium for safety and effectiveness [5], and it does not approve dietary supplements for safety and effectiveness before they are sold [9]. See is kanna legal.
Can I drink alcohol with kanna?
There is not enough research to know whether sceletium interacts with alcohol [5]. With no data, the cautious move is not to combine them.