Dave S writes:

Anemia is a matter of degrees. If your hemoglobin level is 0.1 mg/dl
lower than that particular lab's reference values for normal levels, you
technically are anemic. An abnormal lab value DOES NOT mean you
automatically manifest clinical symptoms.

But it is also possible to have no clinical symptoms on the ground,
and yet show severe symptoms at altitude.

How "dramatic" the effect you are claiming is a function of oxygen
delivery to the tissues, which is multifactorial, not tied SIMPLY to one
value.

Whatever the factors involved, flying while anemic is not a good idea.
You don't want to find out that you have the wrong combination of
factors by passing out at 5000 feet.

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