Intracellular Magnesium and Vitamin D - a few studies
Google Scholar search for "Intracellular Mg" "vitamin d" 659 items June 2022
This free form of Magnesium is rarely measured, but is the most accurate
The plasma/blood form of Magnesium is highly regulated by the body, and is not a good measure
Vitamin D metabolism in magnesium deficient chicks - Dec 1989 -
https://doi.org/10.1016/S0271-5317(89)80161-7Magnesium Supplementation in Vitamin D Deficiency - Feb 2019 - doi:10.1097/MJT.0000000000000538
Skeletal and Hormonal Effects of Magnesium Deficiency - June 2013 - https://doi.org/10.1080/07315724.2009.10719764
Low dietary magnesium intake alters vitamin D—parathyroid hormone relationship in adults who are overweight or obese - Sept 2019 https://doi.org/10.1016/j.nutres.2019.08.003
Low intracellular magnesium in patients with acute pancreatitis and hypocalcemia. - Feb 1990 PDF
Magnesium in the elderly - book chapter 2019?