What are the best supplements for my baby at 6 months of age?

Vitamin D. 6 month old babies need 400 units a day of vitamin d. If they are taking about 30 oz a day of formula, then they will get it from that; otherwise supplement. At 6 months your baby is probably starting solid foods, and another nutrient to consider is iron. Usually an iron supplement is not needed however; feed iron-fortified infant cereals and pureed meats to ensure adequate iron intake.