I was under the impression that vitamin D is absorbed much better if taken together with fats or oils. I would take it with food, not on an empty stomach.

Cautiously playing around with supplements I found melatonin to be effective in aiding sleep quality, though not with time to fall asleep. Any suggestions to that effect?

Have you tried taking melatonin sublingually? The rapid absorption leads to a faster onset of sleepiness, which might help (I get extremely sleepy about 10 minutes after sublingual administration). Sublingual melatonin tablets can be found on Amazon.

That's very interesting -- I noticed the exact opposite effect. Melatonin helps me fall asleep faster, but sleep quality doesn't appear to be much better. I did notice an improvement in sleep quality with ZMA (zinc+magnesium+vitamin B6), and the melatonin+ZMA combo works wonders for sleep.

I've not noticed a difference with generic Kroger brand and other brands of Vitamin D3. Seems to be about the same effect. 5,000IU and 10,000IU aren't noticeably different in my experience, but either are a marked improvement over no supplementation.