So this conversation has gotten me to research this topic a little bit more. I'm not exactly sure if it's actually illegal in the U.S., that's just what the nurses who do my phlebotomy have told me. Though I did find that the American Red Cross does not accept blood from individuals who have hereditary hemochromatosis [1].

My case was discovered when my doctor did an iron work-up as part of checking out my liver. The normal level in men is 12-300 nanograms per milliliter (ng/mL). Mine was very close to 1000 ng/mL at the time. These days my hematologist likes to keep me in the 50-75 ng/mL range.

[1] https://www.redcrossblood.org/donate-blood/blood-donation-pr...