I've held off posting about this for a few days, although I've mentioned it where it seems relevant in replies. For a long time I've often woken up with a headache in the morning, which usually goes away after I've been up for a while and had breakfast. I don't know when this first started but it was several years ago, and I noted it because I never woke up with headaches before that.
While I was away on holiday a fellow traveller suggested that I was low in sodium and should eat some salt. I did this, finding that a little salt on my fingertip tasted really good! The following morning, no headache. A couple of evenings later I did the same thing, and after a few tastes suddenly I was overwhelmed with how disgusting the salt tasted and knew I finally had taken enough!
The good part of this is I have not since had a single morning headache, in fact I wake up feeling remarkably well, and I honestly can't remember when I last was waking up consistently feeling well with no headache or feelings of incipient headache.
I suppose the next step is for me to check my blood pressure somehow to make sure I haven't done anything dangerous. I can say, however, that a couple of years ago, having been on pred for about a year, I noticed my heart seemed to be skipping beats and I often had moments of faintness. My doctor being completely uninterested in this symptom I had to take matters into my own hands. I wondered whether I needed more salt as I've eaten little added salt for many years and did take in a bit more salt with my breakfast, and this seemed to help. But the morning headaches increased in frequency as time went by.
So, just wanted to share this experience in case it helps others.