Always treat the cause and not just the symptoms!
People low in Magnesium have a greater tendency to accumulate Iron in body tissue and Iron accumulation in the Liver is disrupting the optimal function of the 25-Hydroxy enzyme. —

‘Vitamin D Insufficiency and Liver Iron Concentration in Transfusion Dependent Hemoglobinopathies in British Columbia’, Open Journal of Hematology 2015

“...These results indicate an association between increased LIC and vitamin D insufficiency/deficiency, suggesting that liver iron overload may indeed affect vitamin D metabolism. Prospective trials are needed to confirm these results.”
http://rossscience.org/ARTICLE/OJHMT-6-6.php