When is the best time for infants to take vitamin D3?

Infants should begin taking vitamin D3 at 400 IU per day starting at 6 months of age to maintain normal blood levels, which helps promote the absorption of calcium and phosphorus and supports healthy bone development. The dosage of vitamin D3 may be adjusted according to individual circumstances to ensure the infant's health and proper growth. Infants should also receive regular pediatric check-ups to monitor healthy development.