Guide
Chaga mushroom side effects
The documented risk of chaga mushroom is oxalate. Two case reports link chaga powder, at 10-15 g a day in one, to kidney damage from oxalate crystals. We found no liver-injury report and no human trial, so rates for a 1,000 mg capsule dose are unknown.
The documented side effect of chaga mushroom is kidney damage from oxalate, reported in two case reports of people who took chaga powder over weeks to years. Chaga is naturally high in oxalate. No human trial exists, so we do not know how often problems occur at any dose, including the 1,000 mg in our capsule serving.
Oxalate and the kidneys
Oxalate is a compound that can form calcium oxalate crystals; when enough of it reaches the kidneys, the crystals can injure them. The human evidence on chaga is two case reports:
- 2022, Medicine (Baltimore): a 69-year-old man took 10-15 g a day of chaga mushroom powder plus 500 mg a day of vitamin C for about 3 months. He developed acute kidney injury; a biopsy showed calcium oxalate crystals in the kidney tubules. His kidney function recovered about a month after treatment began.
- 2020, Journal of Korean Medical Science: a 49-year-old man took chaga powder, for a skin condition, for about 5 years and presented with end-stage kidney disease and oxalate crystal deposits. The leftover powder was assayed as having extremely high oxalate content. His daily gram dose is not stated.
What these do not show: neither says the powder was mycelium, both are single cases, and neither tells us how common the problem is. Ten to fifteen grams is ten to fifteen times our 1,000 mg serving. We do not know the oxalate content of our mycelium powder, and the label prints no oxalate figure. That unknown is why our label's warning says chaga is naturally high in oxalate and tells people with kidney problems or kidney stones to ask a physician before use.
What we did not find
- Liver: autocomplete suggests people search for liver problems with chaga. We found no liver-injury report. That is not evidence of safety; it means we located nothing either way.
- Digestive upset, headache, rash: no trial measured side effects, so we have no rates. Any ingredient can cause a reaction in someone sensitive; stop and ask a doctor if one occurs. We did not search for or cite allergy reports.
- Drug effects: see chaga mushroom and medications.
Mycelium is not the same as conk
Most chaga literature, tea and the case reports concern powders of unstated tissue, usually conk. A 2025 analysis found grain-fermented mycelium chaga products chemically very different from conk; its authors work for a supplier of wildcrafted chaga, which is a stated conflict of interest. So whether the conk's oxalate content carries over to mycelium on grain is unknown, and we won't assume it either way.
Questions people ask
What are chaga mushroom tea side effects?
The same oxalate concern applies to anything made from the conk. We found no study of tea specifically.
Does chaga mushroom extract or powder have different side effects?
We found no study comparing forms. The case reports concern powder.
What are the risks of chaga mushroom coffee?
We found no study of chaga in coffee. The oxalate point depends on how much chaga you take in total, from all sources.
Are there side effects for dogs?
We found no study of dogs and give no guidance. Ask a veterinarian.
Do the oxalate reports mean stones?
The case reports describe oxalate crystals in kidney tissue, not stones, so we cannot say yes or no beyond what they report. If you have a history of oxalate stones, see who should not take chaga mushroom.
What do the benefits and the risks add up to?
No human trial shows a benefit; see what the research does and doesn't show. Our label for chaga mycelium is 1,000 mg per two capsules, as low as $19.19 a bottle on subscription.
Sources
- Chaga mushroom-induced oxalate nephropathy that clinically manifested as nephrotic syndrome: A case report A 69-year-old man taking 10-15 g a day of chaga powder plus vitamin C for 3 months developed acute kidney injury with oxalate crystals; he recovered with treatment.
- Development of End Stage Renal Disease after Long-Term Ingestion of Chaga Mushroom: Case Report and Review of Literature A 49-year-old man who took chaga powder for years ended up with end-stage kidney disease and oxalate deposits; the leftover powder was very high in oxalate.
- Inonotus obliquus - from folk medicine to clinical use A 2020 review of chaga research says the evidence is mostly cell and animal work and that properly designed human studies are still needed.
- Isolation and characterization of a novel platelet aggregation inhibitory peptide from the medicinal mushroom, Inonotus obliquus A lab and mouse study found a chaga mycelium extract and a peptide from it reduced platelet clumping; no person took part.
- Comparative Study of Chaga (Inonotus obliquus) Dietary Supplements Using Complementary Analytical Techniques Lab analysis of chaga supplements found grain-fermented mycelium products chemically very different from wild chaga conk, and starch-rich.
*These statements have not been evaluated by the Food and Drug Administration. This product is not intended to diagnose, treat, cure, or prevent any disease.
