Vitamin D I'm doing 10k iu a day. But I really have no idea what is best. I took 20k iu before, but I stopped when I started responding more to magnesium & zinc, both of which are dependent on vitamin D to help absorb.
As for magnesium, on an average day 100 mg x 4 spread out through the day is best. It seems to absorb much better if spread out. And I also tolerate it much better with this dose. I don't have to fear overshooting the dose.
Sometimes I have days when I have a super high demand for magnesium. The cues for me are high muscle inflammation, feeling a need to stretch, stretching very hard and getting a pleasurable and slightly itchy feeling stretch. I also tend to feel extremely tired. My mental clarity is passable, however. On these days I can take in around 1-1.5g of magnesium and feel better the more I take.
Potassium deficiency feels different to magnesium deficiency because the stretches don't feel good, and your muscles tend to take around 1s to relax again. Potassium deficiency I don't seem to get as much muscular inflammation, but I get really bad problems with focus and fatigue. Often poor focus and fatigue happen before any muscular symptoms.
Both electrolyte deficiencies I get after b12 and perhaps b2/6/zinc/copper.