Objectives: To evaluate the clinical correlation between vitamin D and children with type 1 diabetes mellitus (T1DM) and provide new basis for the prevention and treatment of T1DM. Methods: Children newly diagnosed with T1DM and treated with 3C therapy in our hospital from 2017 to 2018 were selected

the serum levels of 25-hydroxyvitamin D (25(OH)D) of children with T1DM and children with healthy physical examination were analyzed. According to the levels of 25(OH)D

children with T1DM were divided into 3 subgroups (deficient group

insufficient group and sufficient group). The gender

age

residence

body mass index (BMI)

fasting C-peptide

fasting blood glucose and insulin dosage of three subgroups were compared. The correlation between different tanner stages

gender

season

presence or absence of diabetic ketoacidosis (DKA) and serum vitamin D levels was investigated. Results: The serum level of 25(OH)D in the T1DM group was (42.31±22.01) nmol/L

lower than that in the healthy control group (50.37±22.28) nmol/L

and the difference was statistically significant (P<0.05). In the T1DM group

the fasting C-peptide level of the vitamin D sufficient group was higher than that of the vitamin D insufficient group and the vitamin D deficient group (P<0.05). The fasting blood glucose level and the amount of insulin per body mass in the vitamin D deficit group were higher than those in the vitamin D sufficient group (P<0.05). According to the measurement time of 25(OH)D

all patients can be divided into the group A (from 1 to 3 months

from 10 to 12 months) and group B (from 4 to 9 months)

the level of 25(OH)D in group A was lower than that in group B (P<0.05). The level of 25(OH)D in patients with DKA was lower than that in patients without DKA (P<0.05). Conclusion: Vitamin D deficiency is common in children with T1DM

especially in children with DKA and from 1 to 3 months and from 10 to 12 months. Children with T1DM with sufficient vitamin D can reduce the insulin dosage. It is necessary to strengthen the monitoring and supplement of vitamin D in children with T1DM.