Background: The free-form of vitamin D has been used by many researchers as an index of vitamin D status in health and disease. Several methods are there to estimate free, total, and even bioavailable vitamin D. Objective: The present work was carried out to measure free vitamin D using a special formula suggested by Bikle and Schwartz in 2019, which includes the vitamin D binding protein (VDBP). The results will be used to evaluate the vitamin D status in patients with type 2 diabetes mellitus (T2DM), and its relation to the disease progression. Methods: Sixty-four patients with T2DM and 73 healthy subjects, all from Baghdad city, were enrolled in the current study from March to October 2020. For each participant, fasting blood glucose, hemoglobin (HbA1c), insulin resistance HOMA-IR, and body mass index (BMI) were measured in addition to the total vitamin D and VDBP. Moreover, free vitamin D was calculated by the formula of Bikle & Schwartz. Results: There were highly significant correlations between total vitamin D and absolute values of free vitamin D or its percentage. The difference in total vitamin D was significant between patients and healthy controls with no significant change in VDBP, free and bio-available vitamin D, while free vitamin D% was higher in the patient’s group. Correlations between vitamin D and each of BMI, fasting glucose, HbA1c, and HOMA-IR were not significant; however, there was a negative correlation with BMI and fasting glucose in the healthy control subjects only. The Receiver Operating Characteristic (ROC) curve analysis of vitamin D in the diagnosis of diabetes mellitus was poor. Conclusion: Total vitamin D can represent vitamin D status, but it cannot be used as a factor for diagnosing T2DM. However, it could be of importance to change the glycemic status.

Background: Vitamin D is considered an important regulator of many metabolic processes in the body. Its deficiency was reported to associate with many pathological conditions, with contradicting reports on its role in dyslipidemia. Objectives: To evaluate the role of vitamin D (total and/or free) in improving dyslipidemia of type 2 diabetes mellitus (T2DM). Methods: Sixty-four patients with T2DM, and 73 apparently healthy normal subjects were enrolled in the study from March to October 2020. Their fasting blood glucose, glycated hemoglobin, HbA1c, and serum lipids (cholesterol, its fractions and triglycerides) were measured in addition to total and free vitamin D. Results: There was a significant negative correlation between total vitamin D and each of cholesterol and LDL-C in the diabetic group. The correlations between serum vitamin D and all other lipid parameters (HDL-C, VLDL-C and triglycerides) were non-significant in the diabetic group, while in the control groups none of serum lipids showed significant correlations with vitamin D. Conclusions: The significant negative association of vitamin D with total cholesterol and LDLC in the diabetics reveals the important action of vitamin D in reducing the atherogenic indices, and consequent reduction in the rate of atherosclerosis and cardiovascular disease or stroke.