Those who are older than 50 have unique needs when it comes to multivitamins. According to the Institute of Medicine, older adults may not absorb between 10 and 30 percent of the vitamin B12 in their food. Although the official daily value (DV) for vitamin B12 remains at 2.4 mcg throughout adulthood, some experts advise people over 50 to look for 25 mcg of B12 in their multivitamin. Based on the latest guidelines, the Institute of Medicine recommends 1,200 mg of calcium per day for women over 50 and men over 70. Both men and women over the age of 70 are advised to get 800 IU (international units) of vitamin D daily. Other nutrient needs are largely the same. It's important to know that the vitamin K in multivitamins might interfere with blood-thinning medications like Warfarin, according to the National Institutes of Health. If you take a blood thinner, talk to your doctor about your vitamin K needs before you start taking a multivitamin.