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taking iron supplements for a male is dangerous, my doctor told me years ago, for whatever that is worth

This is very true. Some men have to have regular iron level checks and if their iron is too high, they have to have some blood taken out to lower the levels ( venesection). Definitely get medical advice if you're a male before taking iron supplements.

As someone also in the U.K., check your CO2 levels where you sleep and work.

It can also be vitamin B1 or B12 deficiency.