Cataplex D - Helps with Calcium assimilation problems, nosebleeds, hemorrhage, lack of exposure to the sun, hypotension and low blood calcium. Biologically, the ultraviolet rays from the sun convert skin oil to Vitamin D. Vitamin D picks up calcium from the gut and puts it in the bloodstream. From there, Vitamin F takes it from the blood and deposits it in the tissues. Vitamin F is primarily found in oils. In the event of low levels of Vitamin F, Vitamin D also brings calcium back from the tissues and into the bloodstream.