Cordyceps at Altitude: Hiking, Skiing and Oxygen

Does cordyceps help at altitude? Its reputation comes from the Himalayan plateau, where wild cordyceps grows above 3,000 metres and herders credit it with stamina in thin air. The science is much thinner than the legend. One small human trial found that a Rhodiola and cordyceps supplement improved running endurance after two weeks of training at 2,200 metres. No trial has shown that cordyceps prevents altitude sickness. For that, the proven tools are slow ascent and, where needed, acetazolamide.

This guide is for hikers, skiers and climbers wondering whether cordyceps belongs in their pack. For cordyceps and exercise at sea level, see our article on cordyceps, oxygen use and endurance.

Where Does the Altitude Reputation Come From?

From the plateau itself. Wild Cordyceps sinensis, now classified as Ophiocordyceps sinensis, grows on caterpillar larvae in high meadows of Tibet, Nepal and Bhutan, mostly above 3,000 metres. It has been used in traditional Tibetan and Chinese medicine for centuries, and its link with high-altitude life is part of its story.

That origin doesn't prove an altitude benefit, though. A plant or fungus growing high up doesn't mean it helps people cope with high places. Most supplements today also use a different species, Cordyceps militaris, cultivated on grain or other substrates at low altitude.

Interest grew in 1993, when Chinese runners who broke world records were reported to be taking cordyceps. Those reports were never backed by controlled evidence. They did, however, help make cordyceps a sports supplement.

What Does the Human Research Show?

Very little at altitude. We found one controlled trial. In 2014, Taiwanese researchers gave 18 men either a placebo or a supplement of Rhodiola crenulata (1,400 mg) and Cordyceps sinensis (600 mg) daily, during two weeks of training at 2,200 metres.

After the altitude camp, time to exhaustion in a running test rose by 5.7% in the supplement group against 2.2% with placebo. The supplement group also kept more of its parasympathetic nervous activity, a marker of recovery. Red blood cell counts rose equally in both groups (Chen 2014).

Three limits matter. The trial was small. It combined two ingredients, so we can't know how much was due to cordyceps rather than Rhodiola, which has its own altitude research. And 2,200 metres is a moderate altitude, below the level where acute mountain sickness becomes common.

What About Rhodiola, the Other Half of the Trial?

It matters more than most cordyceps marketing admits. The supplement in the altitude trial gave more than twice as much Rhodiola crenulata as cordyceps: 1,400 mg against 600 mg. Rhodiola is a plant from the same high mountain regions, and it has its own body of research on fatigue and on adaptation to low oxygen.

So when an article says "cordyceps improves performance at altitude" and cites this study, it's giving cordyceps credit for a combination product in which it was the smaller ingredient. The honest reading is that the combination helped in this one small trial, and that nobody knows how the effect splits between the two.

Why would researchers combine them? Partly because both are traditional high-altitude remedies, and partly because combination products are what many athletes actually buy. That's reasonable for a first study. It just doesn't settle the question for cordyceps on its own.

What About Animal and Lab Studies?

They're more encouraging, and less relevant. Several studies have exposed rats or cells to low oxygen and found that cordyceps extracts reduced some markers of stress or damage. Indian defence researchers, for example, reported that extracts of Cordyceps sinensis protected against simulated high-altitude hypoxia in laboratory models (Mishra 2021; Rajput 2020).

These studies are useful for understanding possible mechanisms. They don't show that a capsule will protect a person on a mountain. The doses, the models and the type of exposure are all different from a real trek.

Does Cordyceps Improve Endurance at Sea Level?

Modestly, in some groups. In older adults, 1 g a day of a cordyceps product for 12 weeks raised metabolic threshold by roughly 10% (Chen 2010). In young adults, a blend with Cordyceps militaris improved VO2max after three weeks (Hirsch 2017). But trained cyclists who took 3 g a day for five weeks saw no improvement at all (Parcell 2004).

The pattern suggests that any benefit is small and builds over weeks, and that already-fit people may gain little. If you plan to try cordyceps for a mountain trip, start well before you travel rather than on the day. Our cordyceps dosage guide covers the amounts used in trials.

What Actually Prevents Altitude Sickness?

Acute mountain sickness causes headache, nausea, fatigue, dizziness and poor sleep, usually within hours of arriving above about 2,500 metres. Rarely, it progresses to fluid on the lungs or brain, which can be fatal. The Wilderness Medical Society's guidelines set out what works (Luks 2024):

• Ascend gradually. Above 3,000 metres, avoid increasing your sleeping altitude by more than about 500 metres a day, and take a rest day every three or four days.
• Consider acetazolamide if you're at moderate or high risk. A meta-analysis of 22 trials found it effective at 125 to 375 mg twice daily (Gao 2021). It's a prescription medicine, so ask a doctor before your trip.
• Descend if symptoms worsen. Descent is the most reliable treatment for serious altitude illness.
• Don't ascend with symptoms. Rest at the same altitude until they've resolved.

Cordyceps isn't on that list. If you take it, take it in addition to these steps, never instead of them.

Which Symptoms Should Never Be Ignored?

Two rare forms of altitude illness can kill, and no supplement prevents them. Descend at once and get medical help if you or a companion shows these signs:

• Breathlessness at rest, a persistent cough, or pink frothy sputum, which can signal fluid on the lungs.
• Confusion, unsteady walking, severe headache or unusual drowsiness, which can signal swelling of the brain.

A useful check is to walk heel to toe in a straight line. Someone who can't do it at altitude may be developing brain swelling and shouldn't be left alone or taken higher.

Is Cordyceps Safe to Take on a Trek?

Usually, for healthy adults. The common side effects are mild stomach upset and dry mouth. A few cautions apply in the mountains:

• Blood sugar. Cordyceps may lower blood sugar in theory. If you take diabetes medicine and you're exercising hard and eating irregularly, that's worth discussing with your doctor first.
• Bleeding. Cordyceps may affect clotting. Avoid it if you take blood thinners, unless your doctor agrees.
• Immune medicines. Avoid it if you take immunosuppressants.
• Don't start anything new on the trip. Try cordyceps for a few weeks at home, so a stomach upset at altitude isn't confused with altitude sickness.

Our guide to cordyceps side effects and interactions covers the rest.

What About Skiing and Short Trips?

Most ski resorts sit between about 1,500 and 3,000 metres. Some people get mild altitude symptoms there, especially sleeping above 2,500 metres on the first night. The same rules apply: give yourself time, drink enough water, go easy on alcohol the first evening, and don't push hard on day one.

Cordyceps won't change much on a week's skiing. Any exercise benefit seen in trials took at least three weeks of daily use. If you already take it, carry on; if you don't, there's no evidence to start it just for the trip.

Frequently Asked Questions

Does cordyceps prevent altitude sickness?

There's no evidence that it does. No human trial has tested cordyceps for preventing acute mountain sickness. Slow ascent and, where appropriate, acetazolamide are the proven measures.

Should I take cordyceps before a high-altitude trek?

You can, if it suits you, but start several weeks before so you know how you react. Treat it as a possible small fitness aid, not altitude protection. Follow standard ascent rules regardless.

Can I take cordyceps with acetazolamide?

No interaction is known, but it hasn't been studied. Tell the doctor who prescribes acetazolamide about any supplements you take, including cordyceps.

Does cordyceps increase oxygen in the blood?

There's no human evidence that it raises blood oxygen. In the one altitude trial, red blood cell counts rose equally with the supplement and with placebo, which is the normal response to altitude.

Is wild Tibetan cordyceps better for altitude?

There's no evidence that it is. Wild Ophiocordyceps sinensis is rare and extremely expensive, and most products sold as "cordyceps" today use cultivated Cordyceps militaris. Neither has been proven to prevent altitude sickness.

Related Articles

• Cordyceps, Oxygen Use and Endurance
• Cordyceps Endurance and ATP: Human Studies
• Cordyceps Dosage Guide
• Cordyceps Side Effects and Interactions
• Cordyceps vs Caffeine for Energy

Sources

1. Chen CY, Hou CW, Bernard JR, et al. Rhodiola crenulata- and Cordyceps sinensis-based supplement boosts aerobic exercise performance after short-term high altitude training. High Alt Med Biol. 2014;15(3):371-379. PubMed 25251930
2. Luks AM, Beidleman BA, Freer L, et al. Wilderness Medical Society clinical practice guidelines for the prevention, diagnosis, and treatment of acute altitude illness: 2024 update. Wilderness Environ Med. 2024;35(1 Suppl):2S-19S. PubMed 37833187
3. Gao D, Wang Y, Zhang R, Zhang Y. Efficacy of acetazolamide for the prophylaxis of acute mountain sickness: a systematic review, meta-analysis and trial sequential analysis of randomized clinical trials. Am J Med Sci. 2021;361(5):635-645. PubMed 33587912
4. Chen S, Li Z, Krochmal R, et al. Effect of Cs-4 (Cordyceps sinensis) on exercise performance in healthy older subjects: a double-blind, placebo-controlled trial. J Altern Complement Med. 2010;16(5):585-590. PubMed 20804368
5. Hirsch KR, Smith-Ryan AE, Roelofs EJ, Trexler ET, Mock MG. Cordyceps militaris improves tolerance to high-intensity exercise after acute and chronic supplementation. J Diet Suppl. 2017;14(1):42-53. PubMed 27408987
6. Parcell AC, Smith JM, Schulthies SS, Myrer JW, Fellingham G. Cordyceps sinensis (CordyMax Cs-4) supplementation does not improve endurance exercise performance. Int J Sport Nutr Exerc Metab. 2004;14(2):236-242. PubMed 15118196
7. Mishra J, Khan W, Ahmad S, Misra K. Supercritical carbon dioxide extracts of Cordyceps sinensis: chromatography-based metabolite profiling and protective efficacy against hypobaric hypoxia. Front Pharmacol. 2021;12:628924. PubMed 34512317
8. Rajput R, Sharma P, Mishra J, et al. Bioactive fractions from the Chinese caterpillar mushroom, Ophiocordyceps sinensis (Ascomycetes), elucidate adaptogenic role against hypoxia stress. Int J Med Mushrooms. 2020;22(11):1121-1133. PubMed 33426843