CALCIUM PLUS MAGNESIUM & VITAMIN D-3: Provides 1000mg of calcium 20 mcg (800 IU) vitamin D-3 & 500mg magnesium per serving. STRONG BONES: Calcium is essential for building & maintaining strong, healthy bones. ENHANCED CALCIUM ABSORPTION: Vitamin D & magnesium enhance calcium absorption. BACKED BY SCIENCE: Since 1935, GNC has been committed to meeting the highest standards of quality, safety, and efficacy while applying the most up-to-date advances in nutritional science so you can live well.