Approximately 50% of . citizens are Vitamin D deficient. The numbers are higher among hispanic and black populations. The melanin in darker-skinned people interferes with the synthesis of the vitamin D that starts at the level of the skin when the sun comes into contact with it. Therefore, darker-skinned people tend to be more deficient. Vitamin D is crucial for good health , and may be one of the simplest solutions to a wide range of health problems, from diseases of the eyes to the bowels, and conditions rooted in chronic inflammation and immune dysfunction in particular. It is a common deficiency worldwide, even in sundrenched areas, yet many people, including physicians, are unaware they may be lacking this important nutrient.
Steroid isolation , depending on context, is the isolation of chemical matter required for chemical structure elucidation, derivitzation or degradation chemistry, biological testing, and other research needs (generally milligrams to grams, but often more  or the isolation of "analytical quantities" of the substance of interest (where the focus is on identifying and quantifying the substance (for example, in biological tissue or fluid). The amount isolated depends on the analytical method, but is generally less than one microgram.  [ page needed ] The methods of isolation to achieve the two scales of product are distinct, but include extraction , precipitation, adsorption , chromatography , and crystallization . In both cases, the isolated substance is purified to chemical homogeneity; combined separation and analytical methods, such as LC-MS , are chosen to be "orthogonal"—achieving their separations based on distinct modes of interaction between substance and isolating matrix—to detect a single species in the pure sample. Structure determination refers to the methods to determine the chemical structure of an isolated pure steroid, using an evolving array of chemical and physical methods which have included NMR and small-molecule crystallography .  :10–19 Methods of analysis overlap both of the above areas, emphasizing analytical methods to determining if a steroid is present in a mixture and determining its quantity. 
My theory is that people with 1,25(OH) toxicity have already high 1,25(OH) levels for some reason or cholecalciferol is metabolized by CYP2D6. I’m slow metabolizer, and if any med I’m taking is metabolized by CYP2D6, I got toxicity symptoms since day one. I need to take a quarter of the therapeutic dose so my body could use this medicine correctly. On the other hand, fast metabolizers need to take 4x of the therapeutic dose. It would explain why doses of D3 varies so much in people’s statements. Of course, it’s a fat-soluble vitamin, so weight is an important factor when you adjust the dose, but the pace of your’s liver metabolization is even more important IMO.