In the normal state, blood has no business anywhere except in the confines of the heart and blood vessels and in the sinusoids of the marrow, liver, and spleen. Of the average 5 L of blood, only 2.25 L, or 45%, consists of cells.
Take-away: Calcium and magnesium may best be taken in the evening with food or before nighttime sleep. Since zinc should not be taken with calcium and apart from iron, it is most useful if taken earlier in the day either slightly before/after food. Iron should ideally be taken on an empty stomach and separately from other multivitamin/multimineral combinations.
Claims that zinc is effective in preventing vision loss in the elderly have not been proven. Zinc has not been proven effective in the treatment of porphyria. Injectable zinc is given by or under the supervision of a health care professional. Other forms of zinc are available without a prescription. Once a medicine or dietary supplement has been approved for marketing for a certain use, experience may show that it is also useful for other medical problems.