Cordyceps side effects: what is known, and is it dangerous?

Short answer: Cordyceps is generally well tolerated in studies, with mainly mild side effects such as abdominal discomfort, diarrhea, dry mouth, nausea, reduced appetite, and skin rash (LiverTox, 2026). Take extra care if you use blood thinners, blood sugar-lowering medications, or immunosuppressants, and if you are pregnant or breastfeeding. Another point to consider is product quality, since heavy metals are a known concern with cordyceps.

Last updated: November 4, 2026 · Written by Florian Fermin

If you search for "cordyceps side effects," you'll mostly find lists without sources. Here, I lay out what reliable sources say, and also honestly explain what isn't known. For cordyceps, that's quite a lot.

What side effects of cordyceps have been reported in studies?

Studies mainly report mild side effects from cordyceps: abdominal discomfort, diarrhea, dry mouth, nausea, reduced appetite, and skin rash. This information comes from LiverTox, a database by the U.S. National Institutes of Health on liver injury caused by medications and supplements. According to LiverTox, cordyceps extracts are well tolerated (LiverTox, 2026).

LiverTox found no published cases of acute liver injury caused by cordyceps and considers the likelihood of this to be low. Memorial Sloan Kettering (MSK), a large American hospital with its own herbal database, says that no serious side effects have been reported (MSK, 2022).

A side effect is an unwanted reaction by your body to something you take. The fact that few side effects are observed in small studies does not mean they never occur. Rare symptoms or effects of years of use simply won't show up in such studies.

Is cordyceps dangerous?

For healthy adults who follow the recommended daily dose, sources do not point to serious risks. The more serious cases that have been reported involved prolonged bleeding after a dental procedure and lead poisoning from a contaminated product. Whether cordyceps poses a risk depends mainly on your situation: your medications, pregnancy, and the product’s quality.

The risk mainly arises in three situations:

• You take medications, especially blood thinners, blood sugar-lowering medications, or immunosuppressants. More on this below.
• The product is contaminated, for example with lead or arsenic.
• You’re pregnant, breastfeeding, or allergic to mushrooms or fungi.

Which medications can interact with cordyceps?

An interaction means that a supplement and a medication can change each other’s effects. For cordyceps, sources mainly mention blood thinners and blood sugar-lowering medications. These warnings are largely based on lab research, so no one knows exactly how big the effect is in people.

• Blood thinners (anticoagulants and antiplatelet medications): according to MSK, lab research suggests that cordyceps inhibits platelet clumping and may strengthen the effects of these medications. In addition, a case has been reported of an older patient who took Cordyceps sinensis daily and continued bleeding for longer after having a tooth extracted (Hatton et al., 2018).
• Blood sugar-lowering medications and insulin: according to MSK, lab research suggests that cordyceps may strengthen the effects of these medications. Whether this also happens in people has not yet been established.
• Immunosuppressants: in a Chinese study of 202 people after a kidney transplant, some participants received cordyceps alongside ciclosporin, an immunosuppressant medication, under the supervision of their doctors. In that group, both the dose and blood levels of ciclosporin were lower than in the control group (Li et al., 2009). This combination should therefore be managed by your doctor, not used for self-care.

Do you take any of these medications, or other prescription medications? If so, talk to your doctor or pharmacist first before starting cordyceps. Bring a list of all the supplements you take, including the amounts. If you’re having surgery or a dental procedure soon, also mention that you use cordyceps.

Can you use cordyceps if you’re pregnant or breastfeeding?

As far as we know, safety data on cordyceps during pregnancy and breastfeeding are lacking. The reference sources we used for this article, LiverTox and MSK, say nothing about it. That’s why all our cordyceps packaging advises you to consult your doctor before use if you’re pregnant or breastfeeding.

So I wouldn't use it during that period without consulting your GP or midwife. The same applies to children: supplements aren't intended for them unless a doctor advises otherwise. And if you're allergic to mushrooms or fungi, cordyceps isn't for you.

What about heavy metals and contamination in cordyceps?

Heavy metals are a known concern with cordyceps. In Taiwan, two people were reported to have lead poisoning after using cordyceps powder with an extremely high lead content (Wu et al., 1996). Arsenic is also a known concern in wild Cordyceps sinensis (Li et al., 2019).

Researchers disagree about the level of risk posed by this arsenic. A Chinese study of wild Cordyceps sinensis found that only 8.69% of the arsenic was in its most toxic, inorganic form, and concluded that heavy metals did not pose a clear risk when consumed in reasonable amounts (Zhou et al., 2018). Li et al. (2019), on the other hand, found an unknown form of arsenic and considered it a possible health risk.

Both studies looked at wild cordyceps, while cordyceps used in supplements is almost always cultivated. Still, this doesn't tell you anything about your specific product. Only a lab test can.

A certificate of analysis (CoA) is a lab report for each production batch. It usually lists the measured levels of heavy metals such as lead, cadmium, mercury, and arsenic, as well as microbiological contaminants. Learn how to read one in how to read a CoA. If a CoA isn't available, ask the seller for one.

How can you take cordyceps while keeping the risk of side effects low?

You can reduce the risk of side effects by following the daily dose on the packaging, taking cordyceps with a meal, and choosing a product that has been tested for contaminants. These tips can also help:

• Stick to the daily dose. Find out how much cordyceps to take per day in each form in how much cordyceps per day.
• Take it during or right after a meal, as stated on our packaging. This is also helpful if you have a sensitive stomach.
• Start with the lowest amount on the label, then see how your stomach responds.
• If you use several products containing cordyceps, such as our Mushroom Complex and separate cordyceps capsules, add the amounts together.
• Choose a product with a clear ingredient list and a batch-specific CoA. To find out which form is right for you, read cordyceps powder, capsules, or extract.
• If you notice anything unpleasant, stop taking it and consult your doctor.

What does our cordyceps packaging say?

All our cordyceps packaging carries the same warning: "Do not exceed the recommended daily dose. Consult your doctor before use if you are pregnant, breastfeeding, taking medication, or have a medical condition." Below is the highest amount listed on the packaging for each product.

The ingredient list for all three products includes Cordyceps sinensis, with no fillers. The capsules also contain only a plant-based HPMC capsule. The powder and capsules are organic.

We have a certificate of analysis (CoA) for every batch, which you can request via support@getgoyu.com.

Summary in 3 points

• Cordyceps is generally well tolerated in studies. Reported side effects are mainly mild, such as abdominal discomfort, diarrhea, dry mouth, and nausea.
• If you take blood thinners, blood sugar-lowering medication, or immunosuppressants, or if you are pregnant or breastfeeding, consult your doctor or pharmacist first.
• Heavy metal contamination is a known concern with cordyceps, so choose a product with a batch-specific certificate of analysis.

Frequently asked questions

Does cordyceps have side effects?

Sometimes. The effects mentioned are mainly mild symptoms, such as abdominal discomfort, diarrhea, dry mouth, nausea, reduced appetite, and skin rash.

Is cordyceps dangerous?

For healthy adults who follow the recommended daily dose, the sources do not indicate serious risks. However, be cautious if you take medication and choose a product that has been tested for heavy metals.

Can I use cordyceps if I take blood thinners?

Consult your doctor or pharmacist first. Lab research suggests that cordyceps may increase the effects of blood thinners, and one case of prolonged bleeding has been reported.

Can I use cordyceps while pregnant?

There are no safety data on this. Consult your doctor or midwife.

Can cordyceps cause stomach problems?

Yes, abdominal discomfort, diarrhea, and nausea are listed as mild side effects. Take it with a meal and start with the lowest amount on the label.

Sources

1. Hoofnagle JH. Cordyceps. Updated July 23, 2026. In: LiverTox: Clinical and Research Information on Drug-Induced Liver Injury. Bethesda (MD): National Institute of Diabetes and Digestive and Kidney Diseases. NCBI Bookshelf NBK615916
2. Memorial Sloan Kettering (MSK). Cordyceps. About Herbs, updated February 10, 2022. mskcc.org
3. Hatton MN, Desai K, Le D, Vu A (2018). Excessive postextraction bleeding associated with Cordyceps sinensis: a case report and review of select traditional medicines used by Vietnamese people living in the United States. Oral Surgery, Oral Medicine, Oral Pathology and Oral Radiology, 126(6), 494-500. doi:10.1016/j.oooo.2018.07.005
4. Li Y, Xue WJ, Tian PX, Ding XM, Yan H, Pan XM, Feng XS (2009). Clinical application of Cordyceps sinensis on immunosuppressive therapy in renal transplantation. Transplantation Proceedings, 41(5), 1565-1569. doi:10.1016/j.transproceed.2009.02.085
5. Wu TN, Yang KC, Wang CM, Lai JS, Ko KN, Chang PY, Liou SH (1996). Lead poisoning caused by contaminated Cordyceps, a Chinese herbal medicine: two case reports. Science of the Total Environment, 182(1-3), 193-195. doi:10.1016/0048-9697(96)05054-1
6. Li Y, Liu Y, Han X, Jin H, Ma S (2019). Arsenic Species in Cordyceps sinensis and Its Potential Health Risks. Frontiers in Pharmacology, 10, 1471. doi:10.3389/fphar.2019.01471
7. Zhou L, Wang S, Hao Q, Kang L, Kang C, Yang J, Yang W, Jiang J, Huang LQ, Guo L (2018). Bioaccessibility and risk assessment of heavy metals, and analysis of arsenic speciation in Cordyceps sinensis. Chinese Medicine, 13, 40. doi:10.1186/s13020-018-0196-7
8. Product pages, ingredient lists, and usage instructions for Cordyceps Powder, Cordyceps Capsules, and Cordyceps Extract Capsules by GOYU, accessed November 4, 2026.

Find all forms of our cordyceps on the buy cordyceps page.

This article is for informational purposes and is not medical advice. Dietary supplements are not a substitute for a varied and balanced diet and a healthy lifestyle. If in doubt, if you are pregnant, or if you take medication, consult your doctor or pharmacist.