Kanna Capsules: What Is Inside and How to Read the Label
The capsule is the most common kanna supplement, and the milligram number printed on it may not mean what you think.
Kanna capsules are the form most people mean when they say "kanna supplement," and the search results for them are mostly vendor pages that disagree about how many milligrams belong in one. This post explains what a capsule can contain, why the mg figure is slippery, what is and is not known about onset, and what to check on the label. It describes what studies and labels say. It does not recommend a dose.
A kanna capsule contains either ground Sceletium tortuosum plant material or a concentrated extract, and the label mg may refer to either. The human trials we found used 8 mg or 25 mg a day of one standardized extract [1][2]. We found no study timing onset for capsules, so onset claims are brand estimates. Check the extract name, the amount per capsule and the Supplement Facts panel [4].
What are kanna capsules?
They are dietary supplements that package Sceletium tortuosum, also called kanna, into a capsule, usually as dried ground plant or as a concentrated extract.
WebMD lists capsules among the forms sceletium is sold in, alongside liquid extract, dried ground powder, tea and gummies, and notes that each form may contain different amounts of the plant's chemicals [3]. Traditional use was different: historical accounts describe chewing the dried, fermented plant, and tinctures [5]. Capsules are a modern convenience. For background on the plant itself, see what is kanna.
Because capsules are supplements, the FDA is not authorized to approve them for safety and effectiveness before they are marketed [4]. WebMD adds that the FDA has not confirmed that products contain the ingredients on their labels [3]. That puts the weight on the label and on the maker.
How many mg are in a kanna capsule?
There is no standard amount, and the same mg can describe very different contents.
A 2022 plant-chemistry study found that levels of marker alkaloids in Sceletium varied by collection site and ecotype, and the authors proposed those markers for monitoring commercial products [6]. If the raw plant varies that much, "500 mg of kanna" from ground leaf and "25 mg of kanna" from a concentrated extract are not comparable statements. A third kind of label states milligrams of alkaloids rather than of plant, which is a smaller number again.
The human trials used one specific standardized extract, Zembrin, described in its 3-month safety trial as a 2:1 standardized extract [1]. In a 3-month trial of 37 healthy adults, participants took 8 mg or 25 mg a day [1]. A single 25 mg dose was used in an imaging study of 16 healthy volunteers [2] and in two anxiety-task studies of 20 volunteers [7]. Other trials used 25 mg a day for 8 days in 60 recreationally trained adults [8] and for 3 weeks in 21 healthy adults [9]. Those studies were short, small and in healthy people, and several authors were affiliated with the extract's owner. Their doses do not transfer to a capsule of a different extract or of ground leaf [10]. We cover the reasoning in kanna dosage.
| What the label says | What it may mean | Comparable to the trial doses? |
|---|---|---|
| "500 mg kanna" | Ground plant or an unspecified extract | No way to tell without more detail |
| "25 mg Zembrin" | A named standardized extract, the type used in trials [1][2] | Closest match, though the trials were in healthy volunteers |
| "10 mg alkaloids" | Alkaloid content only | Different unit; not the same as extract mg |
| "Standardized," no detail | Marketing term | Not a guarantee of quality or consistency [11] |
How long do kanna capsules take to work?
No one has published a controlled comparison of onset for kanna capsules, so any specific number is a brand estimate.
The nearest published data are not in people. A 2012 lab study put four kanna alkaloids on pig mouth-lining and intestinal tissue and found they crossed all of them, with lower permeability across the oral tissues than the intestinal tissue [12]. It says nothing about how a swallowed capsule compares with anything else in a human. Our post on kanna drinks vs capsules goes through the format question, and what kanna feels like explains why the trials themselves do not describe an obvious felt effect.
Are kanna capsules safe?
The small amount of human data is reassuring in healthy adults, but it is limited, and medication interactions are the main caution.
In the 3-month trial, vital signs, ECG and bloodwork did not differ from placebo at 8 mg or 25 mg a day. The most common adverse event was headache, which was more frequent in the placebo group; efficacy was not assessed [1]. WebMD lists headache and upset stomach as common side effects, and possible interactions with MAOIs, SSRIs, SNRIs, tricyclic antidepressants, antipsychotics, triptans and St. John's wort. It also says it is not known how sceletium might affect pregnancy, and that breastfeeding safety is unknown [3]. A 2021 review noted the plant had not yet been studied in a clinical population [10].
If you take any of those medicines, are pregnant or nursing, or have a medical condition, ask a doctor or pharmacist first. Details at is kanna safe. Do not read this section as a statement that capsules are risk free.
Kanna capsules vs powder, tincture and drinks
The main differences are how clear the amount is and how much you can adjust it.
| Form | Strength | Weakness |
|---|---|---|
| Capsule | Fixed amount per unit; Supplement Facts panel | Contents range from leaf to extract; see kanna powder |
| Tincture | Liquid; amount per dropper is on the label | Ratio and alcohol content vary; see kanna tincture |
| Tea | Close to some traditional preparations | Amount per cup is hard to state; see kanna tea |
| Ready-to-drink | Single serving, flavored | Extract often unnamed; other ingredients present |
For a product-by-product comparison see our kanna supplements hub, and for cans see the kanna drink ranking.
What should be on a capsule label?
At minimum, a Supplement Facts panel, a named plant part or extract, and an amount per serving you can interpret.
- The extract or plant part. "Sceletium tortuosum extract" says more than "kanna blend." Whether the extract is named and standardized to anything matters more than the headline mg.
- Amount per capsule and servings per bottle. Check whether the mg is per capsule or per serving of several capsules.
- Other ingredients. Fillers, other botanicals and caffeine change what you are actually taking.
- Contact details and lot number. These let a maker answer questions. Our kanna label guide and where to buy kanna go further.
- Claims. Supplement labels cannot claim to diagnose, treat or prevent a disease, and any structure or function claim must carry the FDA disclaimer [11]. A label that promises more is a warning sign.
The NCCIH cautions that "standardized," "verified" or "certified" on a label does not necessarily guarantee product quality or consistency [11]. It is a reason to read the whole panel, not to stop at one word.
This page is general information, not medical advice. These statements have not been evaluated by the FDA. Kanna products are not intended for any disease or health condition. kannadrinks.com is published by Psilly Goose, a kanna drink maker.
References
- 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;19(11):898-904. PubMed
- 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;38(13):2708-16. PubMed
- WebMD. Sceletium: Uses, side effects, interactions. webmd.com
- U.S. Food and Drug Administration. Information for Consumers on Using Dietary Supplements. fda.gov
- Smith MT, Crouch NR, Gericke N, Hirst M. Psychoactive constituents of the genus Sceletium N.E.Br. and other Mesembryanthemaceae: a review. J Ethnopharmacol 1996;50(3):119-30. AGRIS record
- Reddy K, Stander MA, Stafford GI, Makunga NP. Mass spectrometry metabolomics and feature-based molecular networking reveals population-specific chemistry in some species of the Sceletium genus. Front Nutr 2022;9. PubMed
- Reay J, et al. Sceletium tortuosum (Zembrin) ameliorates experimentally induced anxiety in healthy volunteers. Hum Psychopharmacol 2020;35(6):1-7. 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;34(9):2476-81. 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
- Olatunji TL, et al. Sceletium tortuosum: a review on its phytochemistry, pharmacokinetics, biological and clinical activities. J Ethnopharmacol 2021;280:114476. PubMed
- National Center for Complementary and Integrative Health. Using dietary supplements wisely. nccih.nih.gov
- Shikanga EA, et al. In vitro permeation of mesembrine alkaloids from Sceletium tortuosum across porcine buccal, sublingual, and intestinal mucosa. Planta Med 2012;78(3):260-8. PubMed
Frequently asked questions
How long do kanna capsules take to work?
We found no published study that timed onset for kanna capsules, so any figure on a product page is the maker's estimate. Our post on what kanna feels like covers why even the existing trials describe little that participants could feel.
How many mg are in a kanna capsule?
It varies by product and the number can mean different things: plant powder, a concentrated extract, or alkaloids only. The human trials used 8 mg or 25 mg a day of one standardized extract [1][2], and doses of other products are not interchangeable with those. See kanna dosage.
Are kanna capsules safe?
In one 3-month trial of 37 healthy adults, an 8 mg or 25 mg daily dose of a standardized extract did not change vital signs, ECG or bloodwork versus placebo [1]. That is a small, single-extract study. Possible interactions with antidepressants and other serotonergic drugs are the main caution [3]. See is kanna safe.
Are kanna capsules better than powder?
Capsules fix the amount per unit and hide the taste. They do not change what is inside. A capsule of ground leaf and a capsule of concentrated extract can be very different products even at the same mg on the label.
Do kanna capsules interact with medications?
Possibly. WebMD lists MAOIs, SSRIs, SNRIs, tricyclic antidepressants, antipsychotics, triptans and St. John's wort as possible interactions, and says research is incomplete [3]. Ask a pharmacist or doctor before using it.