Is it ok to take calcium, vitamin d3 and magnesium together? or do calcium and magnesium compete for absorption?

OK, to a degree but:: Calcium ; magnesium are often packaged together both in supplements ; foods. They compete a bit; calcium may reduce mag. Absorption but mag. Does not seem to reduce cal. Absorption. Those low in mag. Have difficulty absorbing cal.; if deficient in mag. It may be best to take it separately. http://www.nutraceuticalsworld.com/contents/view_breaking-news/2011-09-14/magnesium-is-key-to-calcium-uptake/.