The Apolipoprotein B (Apo-B) test measures the level of Apo-B, a protein found in low-density lipoprotein (LDL) and other atherogenic lipoproteins, often referred to as “bad cholesterol.” Apo-B is essential for the transport of cholesterol and triglycerides in the bloodstream. High levels of Apo-B are associated with an increased risk of cardiovascular diseases, such as heart attack and stroke, as it reflects the number of potentially harmful cholesterol particles in the blood. This test is used to evaluate lipid-related risks for heart disease, often alongside a standard lipid profile. A blood sample is required for this test.