Objective: To analyze the effect of vitamin D combined with insulin in treating patients with hyperglycemia in pregnancy. Methods: 84 cases of patients with hyperglycemia in pregnancy were selected from January 2023 to January 2025 in our hospital and randomly divided into combined group and single group, with 42 cases in each group. Insulin was used in the single group and vitamin D was added in the combined group. the efficacy, fasting blood glucose (FPG), 2hPG, glycosylated HbA1c, FINS, GL, HOMA-IR, total cholesterol (TC), triglycerides (TG), low-density lipoprotein (LDL-C), hs-CRP, IL-6, TNF-α, and adverse pregnancy outcomes were compared between the two groups. Results: The treatment efficiency was 90.48% higher in the combination group than 73.81% in the single group (P < 0.05); after drug administration, the levels of FPG, 2hPG, HbA1c, FINS, GL, HOMA-IR, TC, TG, LDL-C, hs-CRP, IL-6, and TNF-α were lower in the combination group than in the single group, and the incidence of adverse pregnancy outcomes was 7.14% lower than single group 23.81% lower (P < 0.05). Conclusion: Vitamin D combined with insulin in the treatment of patients with hyperglycemia in pregnancy is effective in controlling blood glucose, improving pancreatic islet function, regulating lipid indexes, controlling inflammatory reactions, and reducing adverse pregnancy outcomes.