I am a 38-year-old recreational hiker with moderate fitness. I was preparing for the Everest Base Camp trek and read about cordyceps being used traditionally by Tibetan herders at altitude. Given that cordyceps literally evolved at 3,000-5,000 meters, using it as altitude support felt like it had a certain poetic logic.
I started 3000mg daily of a quality C. militaris extract 3 weeks before the trek and continued throughout. I was also taking the standard acclimatization approach — gradual ascent, rest days, proper hydration. My trekking partner, similar age and fitness, did not take cordyceps but followed the same acclimatization protocol.
This is anecdotal, not a controlled experiment, but: I handled the altitude transition markedly better than expected and better than my partner. At Namche Bazaar (3,440m), he was headachy and fatigued while I felt tired but functional. At Dingboche (4,410m), the difference was more pronounced — I was able to do a day hike to Nagarjun Peak while he rested. At Gorak Shep (5,164m), I was slow and breathing hard but still moving with reasonable energy. He was miserable and considered turning back.
The breathing effect was the most noticeable thing. At altitude, every breath feels insufficient — you are pulling in air but your body never quite feels like it is getting enough oxygen. With cordyceps, this sensation was present but muted. My breathing felt deeper and more productive. I cannot know whether this was pharmacological or placebo, but it aligned precisely with the traditional Tibetan use case that has persisted for centuries.
Would I take it again for altitude? Absolutely. Would I rely on it as a substitute for proper acclimatization? Absolutely not. It felt like it gave me a modest buffer — maybe equivalent to an extra 500-800 meters of acclimatization — but altitude sickness is serious and no supplement replaces doing it right.