Background <p>In Turkey, free vitamin D drop supplementation is provided during the first 12 months after birth. This study aimed to investigate the effectiveness of the National Vitamin D Supplementation Program among children aged 0–12 months in the Karabük province.</p> Methods <p>The study examined the vitamin D levels of children aged 0–36 months. Data were collected to assess the prevalence of vitamin D deficiency and sufficiency within the age intervals of 0–12, 12–24, and 24–36 months.</p> Results <p>The findings revealed that the majority of children fail to attain the desired vitamin D levels. While only one-fourth of the patients attained adequate vitamin D levels within the first 12 months, this proportion progressively declined to one-tenth as they approached the 36th month.</p> Conclusion and recommendation <p>Reforms are necessary in the current strategy for vitamin D supplementation, which is provided free of charge before the age of one. To enhance the effectiveness of the program, healthcare providers in primary care settings should play a central role. The new strategy should focus on a thorough explanation and, in particular, the implementation of a control mechanism. Such a mechanism can ensure oversight by encouraging reminders.</p>