"Natural" doesn't mean side-effect-free. Functional mushrooms are generally well tolerated, but some people get stomach upset or skin reactions, a few species can interact with common medications, and there are rare reports of serious problems with large amounts. Here's what to know before you start.
Written by Vita Globe Editorial Team | Reviewed against Memorial Sloan Kettering herb monographs, NIH guidance and published case reports
What are the side effects of mushroom gummies?
The most common are mild: nausea, stomach upset, constipation, dry mouth or itching, which have been reported with reishi[1]. Some mushrooms may interact with blood thinners and diabetes medications[1][3][4]. Rare serious cases, like kidney damage from heavy chaga use, involved large amounts over months[3].
Caveat: Much of the safety data comes from case reports and small trials, so rare effects may be under-recognized.
Sources: MSK Reishi · MSK Chaga · MSK Maitake · Verified 2026-09-27
IN THIS ARTICLE
What are the most common side effects?
Most reported side effects are mild and digestive. Memorial Sloan Kettering's reishi monograph lists nausea, insomnia, dry mouth, constipation, vertigo and itching[1]. For shiitake, gastrointestinal upset and sensitivity to sunlight have been reported[2]. In a small maitake extract trial in breast cancer survivors, two of 34 participants withdrew because of mild side effects: one had nausea and joint swelling, and the other a rash and itching[5].
Gummies can also cause mild stomach upset for reasons that have nothing to do with mushrooms, such as taking them on an empty stomach or eating more than the serving size. Following the label and taking them with food often helps.
| Mushroom | Reported side effects (not exhaustive) |
|---|---|
| Reishi | Nausea, insomnia, dry mouth, constipation, vertigo, itching; rare liver injury[1] |
| Shiitake | Linear "whiplash" skin rash, GI upset, photosensitivity[2] |
| Chaga | Rare oxalate kidney injury with heavy, long-term use[3] |
| Maitake | Mild GI and skin reactions in trials; warfarin interaction[4][5] |
Can you be allergic to functional mushrooms?
Yes. People can react to mushrooms like any other food. One well-described example is shiitake dermatitis, a whip-like, linear rash that can appear after eating raw or cooked shiitake[2]. Inhaling mushroom spores has also caused lung inflammation in people who work with them[2], though that's an occupational issue rather than a gummy issue.
If you know you react to mushrooms or molds, check with your healthcare provider before trying a mushroom supplement, and stop if you notice a rash, hives, swelling or trouble breathing.
What rare but serious reactions have been reported?
Kidney injury with chaga. Chaga is high in oxalates. MSK summarizes three serious case reports, including a 72-year-old woman who developed oxalate nephropathy requiring dialysis after taking 4 to 5 teaspoons of chaga powder daily for six months[3][6]. These cases involved large amounts of chaga powder over long periods, which is very different from a small share of a blend, but they're a good reason for anyone with kidney disease or a history of kidney stones to talk to their doctor first. Our chaga guide covers this in more detail.
Liver injury with reishi powder. Rare cases of liver toxicity have been reported with powdered reishi, including one death[1]. Signs of liver trouble include yellowing skin or eyes, dark urine and unusual fatigue; see a doctor promptly if you notice them.
Unlisted ingredients. Some of the most serious "mushroom gummy" problems haven't come from functional mushrooms at all but from psychedelic-marketed products. Our piece on functional vs. psychedelic mushroom gummies explains the difference.
Which medications can mushrooms interact with?
Supplements can interact with prescription drugs, and the NIH recommends telling all your healthcare providers about any supplements you take[7]. For functional mushrooms, these are the interactions MSK flags:
- Blood thinners (anticoagulants and antiplatelets, like warfarin): reishi and chaga may increase bleeding risk, and maitake has been reported to raise INR with warfarin[1][3][4].
- Diabetes medications: chaga and maitake may add to blood-sugar-lowering effects[3][4].
- Immunosuppressants: reishi may affect immune response and potentially reduce these drugs' effects[1].
- Cancer treatment: MSK advises people in active cancer treatment to talk with their care team before using reishi[1].
The honest summary
- Most side effects are mild and digestive.
- Mushroom allergies are real; stop if you get a rash or swelling.
- Serious kidney and liver cases are rare and mostly linked to large amounts of single-mushroom powders over months.
- If you take blood thinners, diabetes medications or immunosuppressants, check with your provider first.
Who should skip mushroom gummies or check first?
- Anyone pregnant or breastfeeding, since there's little safety research in these groups.
- People with kidney disease or a history of kidney stones (chaga's oxalate content)[3].
- People with liver disease.
- Anyone scheduled for surgery or taking blood thinners[1].
- People with diabetes on glucose-lowering medication[4].
- Children, unless a pediatrician recommends it.
Our option
Vita Globe Mushroom Gummies – 10-Mushroom Complex
We list every mushroom in our blend so you can check it against your provider's advice: lion's mane, reishi, cordyceps, chaga, turkey tail, maitake, shiitake, white button, black fungus and royal sun, at 250mg of 10:1 extracts per two-gummy serving. If you're pregnant, nursing, taking medication, or have any mushroom or fungal allergy, please talk with your healthcare provider before use.
Frequently asked questions
Are mushroom gummies safe to take every day?
Functional mushroom gummies are designed for daily use at the labeled serving, and most people tolerate them well. Check with your provider if you have a medical condition or take medications[7].
Can mushroom gummies upset your stomach?
Yes, mild nausea or constipation can happen[1]. Taking them with food and sticking to the serving size often helps.
Are mushroom supplements bad for your kidneys?
For most healthy people, there's no evidence of harm at typical supplement amounts. Kidney injury has been reported with heavy, long-term chaga use because of its oxalate content[3][6].
Can mushroom supplements cause liver damage?
It's rare, but liver toxicity has been reported with powdered reishi[1]. Stop and see a doctor if you notice yellowing skin or eyes or dark urine.
Can I take mushroom gummies with blood thinners?
Talk to your doctor first. Reishi, chaga and maitake have been flagged for possible bleeding-risk or INR interactions[1][3][4].
Sources
- Memorial Sloan Kettering Cancer Center. About Herbs: Reishi Mushroom. Updated May 5, 2026. mskcc.org
- Memorial Sloan Kettering Cancer Center. About Herbs: Shiitake Mushroom. Updated February 14, 2023. mskcc.org
- Memorial Sloan Kettering Cancer Center. About Herbs: Chaga Mushroom. Updated February 20, 2023. mskcc.org
- Memorial Sloan Kettering Cancer Center. About Herbs: Maitake. Updated July 9, 2026. mskcc.org
- Deng G, Lin H, Seidman A, et al. A phase I/II trial of a polysaccharide extract from Grifola frondosa (Maitake mushroom) in breast cancer patients: immunological effects. Journal of Cancer Research and Clinical Oncology. 2009;135(9):1215-1221. doi:10.1007/s00432-009-0562-z
- Kikuchi Y, Seta K, et al. Chaga mushroom-induced oxalate nephropathy. Clinical Nephrology. 2014;81(6):440-444. doi:10.5414/CN107655
- NIH Office of Dietary Supplements. Dietary Supplements: What You Need to Know. ods.od.nih.gov
About the Vita Globe Editorial Team
The Vita Globe Editorial Team researches and writes our wellness content, working from peer-reviewed research, systematic reviews and guidance from bodies such as the NIH and the FDA. We cite our sources inline and update articles when the evidence changes.
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. This article is for informational purposes only and is not a substitute for medical advice. Talk to your healthcare provider before starting any new supplement, particularly if you are pregnant, nursing, taking medication, or caring for a child.
