Some vitamins and minerals work synergistically (vitamin D and vitamin C, for instance, are enhanced when taken in tandem) while other nutrient combinations such as iron and calcium can have negative interactions.

It’s important to check with a health care professional about proper ways of taking vitamins, because more is not always better. In some cases, overuse or improper vitamin combinations can be toxic, resulting in long-term vitamin deficiencies, says Dr. Brynna Connor, a board-certified family medicine physician and health care ambassador at northwestpharmacy.com.

For more combinations to avoid as well as some synergistic combinations, check out this blog article from goodhousekeeping.com.