Most people have been trained to watch one number. Their LDL cholesterol goes up, and they worry. It goes down, and they relax.
I think that’s the wrong number to watch.
Atherosclerosis isn’t caused by cholesterol floating loose in the blood. It’s caused by particles carrying cholesterol getting stuck in the artery wall. Every one of those particles — LDL, VLDL, IDL, lipoprotein(a) — carries exactly one copy of a protein called apolipoprotein B. One particle, one ApoB.
So measuring ApoB counts the particles. Measuring LDL cholesterol estimates how much cargo those particles are carrying in total. Those are not the same question, and they don’t always give the same answer.
ApoB vs LDL cholesterol: where they disagree
Picture two people with an identical LDL of 110. The first has a modest number of large, cholesterol-rich particles. The second has a great many small, cholesterol-poor ones. Same LDL. Very different particle counts, and the second person is at meaningfully higher risk — more particles means more chances for one to lodge in the wall.
This discordance isn’t rare, and it clusters in exactly the people I see most: insulin resistance, high triglycerides, low HDL, extra weight around the middle, metabolic syndrome. That pattern produces many small particles. LDL cholesterol can look reassuring while ApoB is telling a different story.
It cuts the other way too. Some people are told to start a statin on the basis of an LDL that turns out to reflect a smaller number of large, buoyant particles. Their ApoB is fine. That’s a conversation worth having before starting a medication for life.
What to ask for
ApoB is a standard, inexpensive, widely available blood test. It does not require fasting. Most labs run it. Most doctors don’t order it, largely because guidelines were built around LDL for decades before ApoB became easy to measure.
Ask for it by name. If you want a fuller picture, ApoB plus lipoprotein(a) — the latter is largely genetic, measured once in a lifetime, and never checked in most people despite being an independent driver of risk.
What I do with it
I use ApoB as the marker to follow, and then I ask the more interesting question: why is it elevated? For many people the honest answer is insulin resistance and diet, not a lipid problem in isolation. That’s a fixable answer, and fixing it upstream tends to move ApoB along with triglycerides, blood pressure, and how the person feels.
The number is a better number. But it’s still a number, and it’s still pointing at something underneath.
Andrew Rudin, MD is a cardiologist and board-certified cardiac electrophysiologist who takes a natural, root-cause approach to heart health. He sees telehealth patients nationally and internationally through Natural Heart Doctor, and is licensed in New York and Tennessee. He has been quoted as an expert source by Medscape and Men’s Journal, and was profiled in The Village Voice. More at andrewrudinmd.com.
This article is for general education and is not medical advice. It is not a substitute for care from your own physician, and nothing here should be used to start, stop, or change treatment on your own.