Nature Made produces a good calcium citrate and magnesium supplement that is verified by the U.S. Pharmacopeial Convention, according to Nature Made. Nature Made supplements contain no preservatives or artificial colors, and the USP mark of approval means that the ingredient facts on the label are accurate.
Another good supplement is the Kirkland Signature brand, which offers calcium citrate with magnesium and vitamin D3, according to the USP. Of 14 consumer reviews, three complaints involved the large size of the tablets, dislike for the seal and the need for two 250 milligram tablets to equal the 500 milligrams on the label front, according to Costco.com.
Nature Made and Kirkland Signature supplements conform to the U.S. Food and Drug Administration's current Good Manufacturing Practices using sanitary and well-controlled procedures, as of 2015, according to USP.