Relationship Between Insulin Resistance and Vitamin D in Type 2 Diabetes Mellitus (DM)

All eligible patients will be asked to participate in the study after counseling and written consent. The following data will be collected.

I) Demographic \& baseline data of the participants:

* Gender, age, residence (rural or urban), weight and height. * Smoking or alcohol consumption.

II) Medical History of the participants:

* Regarding Type 2 DM: onset of diagnosis, current medications, dosage of medications, adherence to treatment, complications of DM. * Other medical disorders: hypertension, thyroid disease.

III) Clinical and laboratory assessment of the participants:

* Vital signs: Pulse, blood pressure (systolic \& diastolic), temperature and respiratory rate. * Body mass index (BMI): calculated as weight in kilograms divided by the square of height in meters (kg/ m²). * Waist circumference of the participants. * All participants will be fasting overnight (12 hours), and the blood samples will be drawn in the next morning. All blood biomarkers will be tested in the same laboratory. We will measure the following: Fasting blood glucose (FBG), glycosylated hemoglobin (HbA1c), 25-hydroxyvitamin D, albumin, total cholesterol (TC), triglyceride (TG), high-density lipoprotein cholesterol (HDL), low-density lipoprotein cholesterol (LDL), alanine aminotransferase (ALT), aspartate aminotransferase (AST), urea nitrogen (BUN), creatinine (S.cr) and uric acid (UA). * The serum concentration of 25(OH)D will be measured using electro-chemi-luminescence immunoassay. * Triglyceride-glucose index (TyG) will be calculated as (fasting triglyceride (mg/dL) x fasting glucose (mg/dL)/2). * Vitamin D deficiency (VDD) is defined as plasma 25(OH)D \< 20 ng/mL; values 20-30 ng/mL are considered insufficiency; and values \> 30 ng/mL are considered sufficiency. * For those with vitamin D deficiency (25(OH)D \< 20 ng/mL); vitamin D supplementation will be added for correction. * Follow up of the participants after 3 months: vitamin D level (25-hydroxyvitamin D), Triglyceride-glucose index (TyG), waist circumference and glycemic control reflected by glycosylated hemoglobin (HbA1c).