Apolipoprotein B, or ApoB, is the main protein found in lipoproteins such as low-density lipoprotein (LDL) cholesterol and ultra-low-density lipoproteins (chylomicrons). Each of these lipoproteins contains one ApoB particle. So, your ApoB levels can tell you the number of these lipoproteins in the blood, which is why ApoB is considered a better predictor of heart disease risk than LDL cholesterol measurements.
ApoB plays a crucial role in transporting lipids (fats) around the body, but too much ApoB is linked to conditions like atherosclerosis, heart attacks, and strokes, which can affect your lifespan and your quality of life in later years.