Bone alkaline phosphatase 250 U/L is not serious. Bone alkaline phosphatase is mainly secreted from bone, and its secretion gradually increases when there is insufficient calcium salt deposition in bone, and decreases if there is sufficient calcium salt in bone. Therefore, bone alkaline phosphatase is one of the phenotypic markers of osteoblasts, which can directly reflect the activity or functional status of osteoblasts, and can also screen for or assist in the diagnosis of impaired bone calcification due to calcium deficiency or metabolic bone disease of other etiologies. The normal reference value for bone alkaline phosphatase should be less than or equal to 200 U/L. 250 U/L is high but not serious. Because no test is viewed in isolation, if a patient’s bone alkaline phosphatase reaches about 250 U/L, it needs to be analyzed in combination with symptoms and other tests to be meaningful. Bone alkaline phosphatase levels are generally somewhat high in infants and young children, and this indicator reflects the growth of newborn tissue. The high bone alkaline phosphatase level should not be used as a basis for the diagnosis of rickets, but should be used to test the blood level of 1,25-dihydroxyvitamin D3 and to consider vitamin D3 supplementation. 400 IU of vitamin D per day is required for infants during breastfeeding, and no additional calcium supplementation is needed.