For infants who are breastfed or receive less than 1 liter of vitamin D–fortified formula daily, what is the recommended daily vitamin D supplementation?

• A. 200 IU
• B. 400 IU
• C. 600 IU
• D. 800 IU

Answer: (B)

Infants who are breastfed or drink less than 1 liter of vitamin D–fortified formula per day don’t receive enough vitamin D from diet alone, and sun exposure in infancy is variable, so they need a daily supplement. The recommended amount to ensure adequate vitamin D is 400 international units per day. This dose aligns with guidelines and ensures a total intake of about 400 IU daily, since formula provides roughly that amount per liter; if formula intake is 1 liter or more, supplementation isn’t routinely needed. The goal is to prevent vitamin D deficiency and rickets while staying within safe, standard dosing. Higher amounts aren’t routinely indicated unless a clinician specifies a different plan.