Yes, I am still taking 400 mcg of selenium every day on a empty stomach. I have not tried stopping it in recent years, but in the past, every time I stopped it, by health level would drop after about 5 days.
I guess I should retest stopping it at some point. But the trouble is, once I restart, it take another 10 days before my ME/CFS improves again. So then I lose about 2 weeks in a more severe state.
I would say before selenium I was moderate, but bordering on severe. But while taking selenium, it places me at the top end of moderate, nudging on mild. It a very noticeable improvement.
The other thing that has helped me is the
high dose transdermal B12 oils, which deliver a systemic dose of B12 equivalent to an injection. These have improved brain fog and mental clarity a bit, but not really any other ME/CFS symptoms.