Heart & circulation
apoB: the cholesterol number that actually matters
A standard cholesterol test weighs the cargo. apoB counts the delivery trucks, and it's the number of trucks, not the cargo, that decides how much ends up in your artery walls.
Your GP checks total cholesterol, and maybe LDL cholesterol. Both measure one thing: how much cholesterol is floating in your blood. But cholesterol doesn't drift into your artery walls on its own. It's carried there inside particles, and it turns out the number of particles matters far more than the amount of cholesterol they're carrying.
Cholesterol is the cargo. apoB counts the trucks.
Every particle that can lodge in an artery wall (LDL, VLDL, IDL, Lp(a)) carries exactly one protein called apolipoprotein B, or apoB. One particle, one apoB. So when a lab measures apoB, it's effectively counting your artery-clogging particles directly.
Lower apoB
fewer particles
Higher apoB
more particles · same cholesterol
Both carry the same cholesterol. The artery on the right has more particles, so more lodge in the wall and build plaque. That particle count is what apoB measures.
Why it beats a standard cholesterol test
Two people can have the same LDL cholesterol but very different particle counts. This is common if you carry extra weight around the middle, have raised triglycerides, or are insulin-resistant: you make lots of small, dense LDL particles. Each one carries less cholesterol, so your LDL number can look reassuring while the particle count quietly runs high. apoB catches what LDL misses.
What apoB tells you that cholesterol doesn't
As a rough guide, optimal is under about 0.9 g/L, and lower still if you're already at higher cardiovascular risk. Your doctor sets the right target for you. This is a guide, not a diagnosis.
The good news
The things that lower LDL usually lower apoB too: less saturated fat, more fibre and unsaturated fats, regular movement, not smoking, and, where a doctor advises it, medication. You don't need a separate plan, just the right number to track.
Should you test it?
apoB is worth knowing if you want a clearer read on heart risk than total cholesterol gives, especially if you have a family history of early heart disease, raised triglycerides, carry weight around the middle, or simply want the most informative single lipid marker.
- You've been told your cholesterol is 'borderline' and want to know what it really means
- You have a family history of heart attack or stroke before 60
- You have raised triglycerides, high blood sugar, or a larger waist
- You're optimising for the long game and want the marker the evidence favours
For predicting cardiovascular risk, the number of apoB particles is more informative than the concentration of LDL cholesterol they carry.
European Atherosclerosis Society consensus (2021)
apoB is included in our cardiovascular and longevity panels.
See the panels