Multivitamins containing iron should not be taken at the same time as calcium supplements, as calcium interferes with the body's ability to absorb iron, explains Nature Made. Magnesium supplements should also ideally be taken apart from supplements of other minerals, according to ConsumerLab.com.
Most daily vitamin supplements, including multivitamins, vitamin E, vitamin C and B-complex supplements, can be taken together with a meal, according to Nature Made.
For many people, it is most practical to take such vitamins along with their breakfast. Taking B vitamins at this time can help supply energy to start off the day, as B vitamins are involved in converting food into energy. Vitamin C helps the body absorb iron, so taking an iron-containing supplement while drinking orange juice for breakfast can be nutritionally advantageous. If doing so is more convenient, it is also acceptable to take vitamins with another meal of the day, notes Nature Made.
Taking certain vitamins and minerals without food may lead to uncomfortable gastrointestinal effects, such as an upset stomach from iron supplements or diarrhea from taking magnesium, warns ConsumerLab.com. Vitamins A, E, D and K are all fat-soluble vitamins that are absorbed more readily when taken with foods containing fat.