Vitamin D Status Among Infants Aged 1–5 Months in Northwestern Romania: A Single-Center Study and Implications for Infant Care and Management

Background/Objectives: Vitamin D is essential for calcium and phosphorus homeostasis and bone mineralization in infancy; serum 25-hydroxyvitamin D [25(OH)D] is its main biomarker. In Romania, data on vitamin D status among infants younger than six months remain limited, despite evidence of suboptimal status in other Romanian pediatric and perinatal populations. This study aimed to assess vitamin D status in infants aged 1–5 months in northwestern Romania and its associations with supplementation dose, feeding type, and season of blood sampling.