Cordyceps, what it is, benefits, side effects and dose

High on the Tibetan Plateau, above 3,000 metres, a fungus grows inside caterpillars buried in the soil. By early summer a thin, dark stalk pushes up through the grass, which is why it's called "winter worm, summer grass" [1]. The cordyceps in UK capsules is grown very differently.

Cordyceps is a fungus used in traditional Tibetan and Chinese medicine. Today it's sold as a supplement for energy and exercise. Small trials have found some changes in exercise tests, and others found none [2].

What is cordyceps?

Cordyceps is a group of fungi that grow on insects. The best known, Ophiocordyceps sinensis (once called Cordyceps sinensis), lives on moth caterpillars in the mountains of Tibet, western China, Nepal, Bhutan and India [1].

Wild cordyceps is rare and hard to collect. Its price has been put at 20,000 to 40,000 US dollars a kilo, which is why it's called "soft gold" in China [1]. So almost all cordyceps on sale is grown in a lab, without a caterpillar in sight.

Cordyceps sinensis or militaris?

Cordyceps supplements are usually one of two things. The label may say Cordyceps sinensis or "Cs-4", which is usually mycelium, the root-like threads, grown in tanks of liquid [1]. Or it may say Cordyceps militaris, a related species that's easier to grow [3].

Wild cordyceps, lab-grown mycelium and militaris don't contain the same mix of compounds. A review of 152 studies found that at least 116 used material that was unreliable, uncertain or not described [1]. Some products are also mycelium grown on grain, such as the oat-grown blend used in one exercise trial [3].

So check the label for the species, the part (fruiting body or mycelium) and the amount in a day's dose.

What is cordyceps good for?

The label says energy and stamina. The trials say it's too early to tell. Many studies looked at exercise, and the results are mixed [2].

A 2025 review of trials in athletes found three trials of Cordyceps sinensis at 2 to 3 g a day. Two, in runners, found better endurance and aerobic fitness, and one, in cyclists, found no change [2]. Mixed

Cordyceps has also been tested on the immune system. In 79 healthy Korean men, 1.5 g a day of Cordyceps militaris for 4 weeks raised the activity of natural killer cells, a type of white blood cell, more than a placebo [7]. Early

No health claim for cordyceps is authorised in Great Britain [8]. So a pack can't legally promise that it boosts energy or immunity.

Is cordyceps safe?

Trials have reported few side effects, but many didn't report on them. In the 2025 review, only 3 of 14 trials mentioned side effects at all [2].

Lab studies suggest cordyceps may lower blood sugar and slow blood clotting. So speak to your GP or pharmacist first if you take diabetes medicines or a blood thinner such as warfarin. One person had heavy bleeding after a tooth was taken out while using cordyceps every day [9].

We found no safety studies in pregnancy or breastfeeding, so it's best avoided then.

How much cordyceps should you take?

There's no agreed dose. Trials in healthy people gave 1 g to 4 g a day, as capsules or tablets, for 1 to 12 weeks [3][4][5]. One trial gave a single 1 g dose 30 minutes before exercise [6].

Follow the dose on your product's label. Because products differ so much, a dose from one trial doesn't carry over to a different species or part.

Where Nooroots fits

Nooroots doesn't make a cordyceps supplement. If you're curious about mushrooms for focus, our guide to lion's mane covers a mushroom studied for memory and focus. Our guide to mushroom coffee looks at the blends that often include cordyceps.

Frequently asked questions

What does cordyceps do to your body?

Small trials have looked at exercise and immune markers. Some found better endurance or aerobic fitness, and others found no change, so the evidence is mixed [2].

Is cordyceps dangerous?

Trials have reported few side effects. It may add to the effects of diabetes medicines and blood thinners, so check with your GP or pharmacist first if you take them [9].

Is Cordyceps militaris or sinensis better?

We found no trial comparing them directly. Both have been tested in small exercise trials, with mixed results, so the label's species, part and amount matter more [2][3].

Can you take cordyceps every day?

Trials gave it daily for up to 12 weeks [5]. There's little research on longer use.

How long does cordyceps take to work?

Trials ran from a single dose to 12 weeks. One found no change after 1 week but a rise in fitness in a small group after 3 weeks [3].

Is cordyceps legal in the UK?

Cordyceps is sold in the UK as a food supplement. No health claim for it is authorised, so packs can't say it improves energy or immunity [8].

Read more in our guide to rhodiola rosea, another supplement tested for energy and exercise.

References

Every study here is listed so you can read it yourself. This guide is for general information and doesn't replace advice from your GP or pharmacist. We check it again at least every six months.

1. Lo HC, Hsieh C, Lin FY, Hsu TH (2013). A systematic review of the mysterious caterpillar fungus Ophiocordyceps sinensis in DongChongXiaCao and related bioactive ingredients. Journal of Traditional and Complementary Medicine 3(1): 16–32. PMID 24716152
2. Shu MY, Zhang XC, Zuo L, et al. (2025). Effects of fungal supplementation on endurance, immune function, and hematological profiles in adult athletes: a systematic review and meta-analysis. Frontiers in Nutrition 12: 1670416. PMID 41280379
3. Hirsch KR, Smith-Ryan AE, Roelofs EJ, Trexler ET, Mock MG (2017). Cordyceps militaris improves tolerance to high-intensity exercise after acute and chronic supplementation. Journal of Dietary Supplements 14(1): 42–53. PMID 27408987
4. Parcell AC, Smith JM, Schulthies SS, Myrer JW, Fellingham G (2004). Cordyceps sinensis (CordyMax Cs-4) supplementation does not improve endurance exercise performance. International Journal of Sport Nutrition and Exercise Metabolism 14(2): 236–242. PMID 15118196
5. Chen S, Li Z, Krochmal R, Abrazado M, Kim W, Cooper CB (2010). Effect of Cs-4 (Cordyceps sinensis) on exercise performance in healthy older subjects: a double-blind, placebo-controlled trial. Journal of Alternative and Complementary Medicine 16(5): 585–590. PMID 20804368
6. Farzan H, Koushkie Jahromi M (2026). Acute Cordyceps militaris supplementation and elevated resting oxygen uptake with faster reaction times: a randomized crossover trial. PLoS One 21(7): e0351725. PMID 42455764
7. Kang HJ, Baik HW, Kim SJ, et al. (2015). Cordyceps militaris enhances cell-mediated immunity in healthy Korean men. Journal of Medicinal Food 18(10): 1164–1172. PMID 26284906
8. Department of Health and Social Care. Great Britain nutrition and health claims (NHC) register, spreadsheet of 19 May 2026. Accessed 26 October 2026. gov.uk
9. Memorial Sloan Kettering Cancer Center. About Herbs: Cordyceps. Last updated 10 February 2022. Accessed 26 October 2026. mskcc.org