There is a genetic/acclimatization factor at work here, too. Some decades ago, I was dating a nurse at Loma Linda. She suggested that I donate blood, which I did. Several days later, the hospital called & asked me to come in for a visit. They told me that I had recorded the highest hemoglobin & clotting factor they had ever seen. We discussed my life-style, and when I mentioned that I was climbing 12-14 thousand-foot mountains several times a month, they asked me to give blood every 3 weeks, so that they could spin down platelets. And they paid me!
That was then. Now, after three blood-clot episodes, I just depend on rat-poison. Every day.
