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Safety

Does cordyceps cause diarrhea?

Written by the Full Measure editorial team, which sells supplements. Approved for publication by the Full Measure owners. Updated .

Drafted with AI assistance from the sources listed below. How we write these

Quick answer

NIH's LiverTox lists diarrhea among minimal or mild side effects of cordyceps extracts, with abdominal discomfort, dry mouth, nausea, poor appetite and rash. Trials of 1 to 4 g a day report few side effects, and in a 2025 review only 3 of 14 trials in athletes mentioned adverse events. No source gives a rate for diarrhea.1,2

Key facts

  • LiverTox says cordyceps extracts are well tolerated, with only minimal or mild adverse events that can include abdominal discomfort, diarrhea, dry mouth, nausea, poor appetite and rash.1
  • In a 2025 review of 14 trials of mushroom supplements in athletes, only 3 mentioned adverse events at all.2
  • A 4-week trial of 1.5 g a day of Cordyceps militaris in 79 healthy men reported no statistically significant adverse reaction.3
  • An 8-week trial of 1.68 g a day of a cordyceps mycelium extract in 79 adults reported no serious adverse events.4
  • No source we read gives a rate for diarrhea, or compares the forms of cordyceps sold.1

What NIH's liver injury database says

LiverTox covers cordyceps because the question is whether it harms the liver, and rates it an unlikely cause of clinically apparent liver injury. Its background section also describes tolerability. It says cordyceps extracts are well tolerated and have only minimal or mild adverse events, which can include abdominal discomfort, diarrhea, dry mouth, nausea, poor appetite and rash.1

The entry gives no rates for any of these. It adds that doses in commercial products range from 0.5 to 4 g a day, and that most products in use are not made from the natural fungus but from a laboratory-grown version called Cs-4.1

What the trials reported

Trials of 1 to 4 g a day reported few side effects. In a 3-month study of 1.05 g a day of a related species, liver and kidney blood tests did not change and no one reported side effects.3,4,5

In the 4-week trial, 39 men took 1.5 g a day of Cordyceps militaris and 40 took placebo, and the report states there was no statistically significant adverse reaction.3

In the 8-week trial of a mycelium extract, 79 healthy adults took 1.68 g a day or placebo, and no serious adverse events were reported. Pregnant and breastfeeding women were not included.4

In a trial of 40 healthy adults who drank a Cordyceps militaris beverage for 8 weeks, safety blood tests did not differ from placebo.6

Why a missing report is not a clean answer

In a 2025 review of 14 trials of mushroom supplements in athletes, only 3 mentioned adverse events, so mild complaints may have gone unrecorded.2

A paper that does not mention diarrhea has therefore not shown that none occurred. That is why LiverTox's list of possible effects and the trials' silence can both be true, and why no source here gives a rate.1,2

What is in the product

Cordyceps is the common name for several fungi that live on insects, and the products on shelves differ. LiverTox says most are a laboratory-grown mycelium, while trials have also used Cordyceps militaris, taken as capsules or as a drink.1,6

Lead poisoning from contaminated cordyceps powder: two cases in Taiwan, where the powder held up to 20,000 ppm of lead. Blood lead returned to normal after they stopped taking it.7

That case is from 1996 and concerned a powder with a very high lead content. It is listed because it shows why the maker and the contents of a product matter, not because it describes products sold today.7

Other causes of diarrhea

MedlinePlus lists bacteria, viruses and parasites in food or water, medicines such as antibiotics, and food intolerances among the common causes of diarrhea, and says sometimes no cause can be found. A person who starts cordyceps and then has diarrhea therefore cannot assume the supplement caused it. A doctor or pharmacist can look at everything a person takes.8

For adults, MedlinePlus says to contact a provider for signs of dehydration, diarrhea beyond 2 days, severe pain, a fever of 102 degrees or higher, or stools with blood, pus or a black, tarry look.8

Who should ask a doctor or pharmacist first

  • Anyone who takes medicines that suppress the immune system, or who has an autoimmune condition, because trials found raised natural killer cell activity with cordyceps.3,4
  • Anyone with liver disease. LiverTox says cordyceps should be stopped in a person who develops evidence of cirrhosis or portal hypertension, and describes one 2023 case of a rare chronic liver condition in a long-term user that makes the link uncertain.1,9
  • Anyone who is pregnant or breastfeeding. One of the trials excluded them, and we found no study in either group.4

Questions people ask

Does cordyceps cause constipation?

LiverTox lists diarrhea, not constipation, among the mild side effects of cordyceps extracts, and none of the trial summaries we read mentions constipation. Ask your doctor if bowel changes follow a new supplement.1

Does cordyceps cause stomach upset?

LiverTox lists abdominal discomfort, nausea and poor appetite among minimal or mild adverse events of cordyceps extracts. The trials we read report few side effects, and a 2025 review found most trials in athletes did not mention them.1,2

Does cordyceps cause dry mouth?

LiverTox lists dry mouth among the minimal or mild adverse events that can occur with cordyceps extracts. It gives no rate.1

How long does diarrhea from cordyceps last?

No source says how long diarrhea from cordyceps lasts. MedlinePlus says diarrhea from any cause usually lasts one or two days, and tells adults to contact a provider if it lasts more than 2 days.8

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Sources

  1. Cordyceps. In: LiverTox: Clinical and Research Information on Drug-Induced Liver Injury. Bethesda (MD): National Institute of Diabetes and Digestive and Kidney Diseases; 2012 onward. References updated July 23, 2026. Read from the chapter text in NIH's LiverTox open-access archive. Opened 2026-10-11.
  2. Shu MY, Zhang XC, Zuo L, Jiang FL, Liang J, Li F. Effects of fungal supplementation on endurance, immune function, and hematological profiles in adult athletes: a systematic review and meta-analysis. Front Nutr. 2025;12:1670416. Opened 2026-10-07.
  3. Kang HJ, Baik HW, Kim SJ, et al. Cordyceps militaris enhances cell-mediated immunity in healthy Korean men. J Med Food. 2015;18(10):1164-1172. Opened 2026-10-07.
  4. Jung SJ, Jung ES, Choi EK, Sin HS, Ha KC, Chae SW. Immunomodulatory effects of a mycelium extract of Cordyceps (Paecilomyces hepiali; CBG-CS-2): a randomized and double-blind clinical trial. BMC Complement Altern Med. 2019;19(1):77. Opened 2026-10-07.
  5. Tsai YS, Hsu JH, Lin DP, et al. Safety assessment of HEA-enriched Cordyceps cicadae mycelium: a randomized clinical trial. J Am Coll Nutr. 2021;40(2):127-132. Opened 2026-10-07.
  6. Ontawong A, Pengnet S, Thim-Uam A, et al. A randomized controlled clinical trial examining the effects of Cordyceps militaris beverage on the immune response in healthy adults. Sci Rep. 2024;14(1):7994. Opened 2026-10-07.
  7. Wu TN, Yang KC, Wang CM, et al. Lead poisoning caused by contaminated Cordyceps, a Chinese herbal medicine: two case reports. Sci Total Environ. 1996;182(1-3):193-195. Opened 2026-10-07.
  8. MedlinePlus Health Topics. Diarrhea. National Library of Medicine; content from the National Institute of Diabetes and Digestive and Kidney Diseases. Read October 11, 2026. Opened 2026-10-11.
  9. Kaur B, Vipani A, Trivedi H, et al. Traditional Chinese medicine, Cordyceps, related to hepatoportal sclerosis. ACG Case Rep J. 2023;10(12):e01206. Opened 2026-10-07.

This page is information, not medical advice. Talk to your doctor or pharmacist about your own situation.