Just give blood...
Literally, that's the treatment, it's the only way to remove stuff like iron. They even do an iron test Everytime, although they're looking for people under and not over the limit.
And I've never heard "Celtic curse" it's how people survived famine and no access to iron in their food supply. We're just super efficient at absorbing it. And modern diets are too high in iron
Unless, you just give blood. Which again, is the prescribed treatment if you ever test too high.
So just give blood routinely and be comfortably under the limit.
It's the easiest "curse" in the world to manage. Hell, leeches and bloodletting have been around for milenia as common treatments.
For much of recorded history, you'd stumble into proper treatment,. literally, from just bleeding