Apolipoprotein B is the structural protein carried by LDL, VLDL, IDL and lipoprotein(a) particles, one molecule per particle. Measuring it therefore counts the atherogenic particles in the blood rather than the cholesterol packed inside them. It is used in the lipid profile as a direct measure of the particle burden that can enter the artery wall.
No readings for this marker yet.
Higher apolipoprotein B is seen most often with raised LDL and non-HDL cholesterol, and with insulin resistance, obesity, type 2 diabetes, hypothyroidism, kidney or liver disease, or familial lipid disorders; it can be high even when LDL cholesterol looks acceptable, particularly when triglycerides are raised and particles are small. Lower values usually accompany a favourable lipid pattern, and rarely reflect an inherited deficiency, malabsorption or an overactive thyroid. An isolated result is confirmed on repeat testing and interpreted with a doctor against the full risk picture.
The value shifts with recent acute illness, pregnancy and marked weight change, and assays are standardised, so switching laboratories can move the number slightly. It is read together with LDL cholesterol and non-HDL cholesterol, which it should broadly agree with, and with triglycerides, since discordance appears most often when those are high; lipoprotein(a) contributes some of the measured apolipoprotein B and is assessed separately.
Reference ranges are general adult values and depend on lab, assay, age and sex. For orientation, not diagnosis — discuss results with your doctor.