ergocalciferol

But of course, if you're taking "vegan-friendly" D supplements, it's almost always a fungal source which of course is the deficient D2 ergocalciferol form. I would suggest UV lamps at your desk instead of supplements.

At her regular checkup, my wife was prescribed ergocalciferol for a rather pronounced vitamin D deficiency. She said she felt like a new person after taking it.

The Rx concentrations are higher and generally cholecalciferol instead of ergocalciferol which is less absorbable and not as long-lasting. It’s fine to try it out.

If you supplement vitamin D at hogh doses, make sure you use cholecalciferol rather than ergocalciferol. The former is naturally synthesized in your own skin, whereas the latter is produced mainly in mushrooms, and can result in unpleasant side effects.

I thought all D2 and D3 supplements would be ergocalciferol and cholecalciferol, respectively, while calcitriol is what gets tested to assess blood levels. Do any supplements actually contain calcitriol?

Full "ergocalciferol should not be regarded as a nutrient suitable for supplementation or fortification." D2 and D3 are metabolized so differently that they result in the "production of unique biologically active metabolites."

There is some question as to whether ergocalciferol--a chemical mainly found in fungi that produce ergosterol and have been exposed to UVB light--is biologically equivalent to cholecalciferol in humans. It can alleviate vitamin D deficiency symptoms, but it is not known with certainty whether it can produce a sufficiency. As far as I am aware, the known cases of hypervitaminosis D have resulted from ergocalciferol supplementation, rather than from cholecalciferol.

Vitamin-D2 aka ergocalciferol works similar in that is is eventually converted by liver and kidneys into calcitriol. Ergocalciferol, calcifediol and it's various precursors can indeed be stored in fat tissue.