What is ApoB, and should you test it?

Most people know their cholesterol number. Far fewer know their ApoB, and it's arguably the more useful of the two.

What it actually measures

Cholesterol doesn't float around in your blood on its own. It travels inside particles: LDL, VLDL, IDL and Lp(a). Every one of those particles carries exactly one molecule of a protein called apolipoprotein B, or ApoB.

So when you measure ApoB, you're counting the particles themselves. A standard LDL cholesterol test measures something different: how much cholesterol those particles are carrying in total.

That difference matters because it's the particles that do the damage. They slip into the artery wall, get stuck, and start the process that becomes plaque. More particles means more chances for that to happen, regardless of how much cholesterol each one carries.

When LDL and ApoB disagree

For many people, LDL cholesterol and ApoB tell the same story. But they can split apart, especially in people with high triglycerides, a large waist, insulin resistance or type 2 diabetes. In those cases the particles tend to be smaller and more numerous. LDL cholesterol can look fine while ApoB, the actual particle count, is high.

That's why European cardiology guidelines recommend ApoB as part of risk assessment, particularly for people with high triglycerides, diabetes or obesity.

What's a good number?

Standard lab ranges often flag ApoB only above about 120–130 mg/dL. Guidelines set lower targets the higher your overall risk: below 100 mg/dL for moderate risk, and lower still for high-risk groups.

In the Longevity Journal we use two targets:

• Advanced level: below 90 mg/dL
• Optimized level: below 70 mg/dL

These are optimal targets for long-term prevention, not diagnoses. If your number is high, talk to your doctor, especially if heart disease runs in your family.

How to test it

ApoB is a normal blood test from the same draw as the rest of your panel. It doesn't need fasting. Most GP panels don't include it by default, so ask for it by name. Privately, it's usually a small add-on to a standard panel. If you're testing for the first time, add Lp(a) as well: it's largely genetic, it raises risk independently, and you only need to test it once.

What moves it

• Saturated fat. Less butter, fatty meat and processed meat; more olive oil, nuts and fish.
• Fibre. Oats, beans, lentils and psyllium help lower the particles in your blood.
• Weight and waist. Losing excess fat, especially around the middle, often brings ApoB and triglycerides down together.
• Alcohol and refined carbohydrates, which drive up triglycerides and the particles that carry them.
• Medication, when lifestyle isn't enough. Genetics play a big role for some people, and that's a conversation for your doctor, not a failure of willpower.

The bottom line

If you only test one heart marker beyond blood pressure, make it ApoB. It counts what actually causes the problem, and it's cheap to add to a panel you're already having.

In the journal: ApoB is on the Advanced page. If it's your bottleneck, "beans or oats today" or "no processed meat" make good daily boxes.

Sources: Mach et al., ESC/EAS Guidelines for the management of dyslipidaemias, European Heart Journal 2020 · Sniderman et al., JAMA Cardiology 2019 · Ference et al., European Heart Journal 2017.