Quite a few years ago I was suffering from lots of lethargy. I thought it might just be some kind of sleep apnea. A few blood tests showed an alarmingly high concentration of calcium in my blood which appeared to explain several secondary symptoms. I also have a family history of thyroid issues which is linked to it.

Cutting out vitamin d rich sources and most calcium rich sources had me back to normal within a few weeks. I'm back on calcium rich sources now without, much problem, but still need to watch for high vitamin d sources or the issues return.