Objective To explore the interactive effect of vitamin D and triglyceride （TG）/high-density lipoprotein cholesterol （HDL-C） on the time to achieve glycemic control in hospitalized patients with type 2 diabetes mellitus （T2DM）. Methods A retrospective cohort study was conducted on 82 T2DM patients admitted to Henan Hongli Hospital from March 2021 to December 2023. Patients were categorized into two groups based on the time it took for their blood glucose to reach target levels during their hospitalization： the ≤ 7 d group and the > 7 d group. The baseline data， vitamin D levels， and TG/HDL-C ratios of both groups were compared. The relationship between vitamin D， TG/HDL-C levels， and the time it took for blood glucose to reach target levels was analyzed. Furthermore， the TG/HDL-C levels of patients with varying vitamin D levels were compared， and the relative risk （RR） and receiver operating characteristic （ROC） curve were used to analyze the interactive effect and predictive value of vitamin D and TG/HDL-C levels on the time it took for hospitalized T2DM patients to achieve target blood glucose levels. Results The hospitalization duration of the group with a duration of > 7 days was longer than that of the group with a duration of ≤ 7 days. The fasting blood glucose， glycosylated hemoglobin， and TG/HDL-c levels were higher in the former group， while the vitamin D level was lower. The proportion of patients with vitamin D deficiency and severe deficiency was higher in the former group compared to the latter group （P < 0.05）. Pearson correlation analysis revealed that vitamin D level was negatively correlated with the time to achieve glycemic control （r = -0.733， P < 0.001）， while TG/HDL-C level was positively correlated with the time to achieve glycemic control （r = 0.830， P < 0.001）. After adjustment， logistic regression analysis indicated that vitamin D （95%CI： 0.482 ~ 0.694） and TG/HDL-C level （95%CI： 1.053 ~ 1.392） remained independent factors influencing the time to achieve glycemic control in hospitalized T2DM patients （P < 0.05）. Patients with insufficient， deficient， and severely deficient vitamin D had higher TG/HDL-C levels compared to those with sufficient vitamin D （P < 0.05）. The relative risk （RR） of patients with vitamin D deficiency and elevated TG/HDL-C coexisting resulting in a hospitalization duration of > 7 days for T2DM patients was 15.867， indicating a synergistic effect. The area under the receiver operating characteristic （AUC） curve for predicting the time to achieve glycemic control in hospitalized T2DM patients using a combination of vitamin D and TG/HDL-C was 0.929， which was greater than that of vitamin D and TG/HDL-C alone （Z = 3.849， 3.526， P < 0.05）. Conclusion The vitamin D and TG/HDL-C levels in hospitalized T2DM patients are closely related to the time of reaching glycemic targets. The simultaneous exposure of both factors can affect the time of achieving glycemic targets， and the combined prediction of vitamin D and TG/HDL-C has good reference value for predicting the time of achieving glycemic targets in hospitalized T2DM patients.