Innovative instruments to stem the tide of cardiometabolic diseases are needed, especially in primary care (PC). A measurement of the ratio: triglycerides (TG) to HDL-Cholesterol (HDL-C), known as atherogenic dyslipidemia index (TG/HDL-C) (a biomarker of plasma atherogenicity & insulin resistance), may be helpful in PC, since it can shed some light on early detection of asymptomatic patients with high cardiovascular (CV) risk. This work explores the correlations between TG/HDL-C, lipid and anthropometric parameters, coronary heart disease (CHD) and type 2 diabetes mellitus (T2DM), in PC patients. This analysis reports that the increased TG/HDL-C positively correlates with obesity and diabetes. Thus, TG/HDL-C may serve as a simple tool for the identification of patients, who may be at high risk for CHD or diabetes, despite achieving the recommended LDL-C levels. This book, therefore, proposes TG/HDL-C as a novel marker, which should be useful to PC practitioners, cardiology and diabetology specialists, pharmacists, dietitians, nurses, rehabilitants, and health educators. Also, researchers may consider this marker for future design of prospective randomized clinical trials.