- Every particle that can cause artery plaque carries exactly one apoB protein, so apoB is a direct count of harmful particles.
- When LDL cholesterol and particle count disagree, risk follows apoB more closely.
- European targets are under 100, 80 or 65 mg/dL depending on your risk.
- ApoB is most useful if you have high triglycerides, diabetes, obesity or metabolic syndrome, or a very low LDL.
Your standard cholesterol test measures how much cholesterol is being carried in your blood. But plaque is not caused by cholesterol floating around on its own. It is caused by particles that carry cholesterol into artery walls. The more of these particles you have, the more chances each day for one to get stuck.
ApoB is a simple blood test that counts those particles. It is not yet routine in every country, but many heart and lipid specialists now see it as the most accurate single marker of cholesterol-related risk. Here is what it measures and when it is worth asking for.
One apoB per harmful particle
Apolipoprotein B (apoB) is the main structural protein wrapped around the lipoproteins made by the liver. It works like a label: each particle gets one copy, and keeps it for life. That makes apoB different from cholesterol, because the amount of cholesterol per particle varies, while the number of apoB molecules per particle does not.
About 90% of apoB particles in the blood. The main plaque builder.
Triglyceride-rich particles that shrink into cholesterol-carrying remnants. Higher when triglycerides are high.
An LDL-like particle with an extra protein attached. Mostly set by genes.
HDL particles carry a different protein, so they are not counted in apoB.
Sniderman et al., JAMA Cardiology 2019.
So a single apoB number adds up all the particles that can enter the artery wall: LDL, VLDL, remnants and Lp(a). An LDL cholesterol result only reflects the cholesterol inside one group of them.
When LDL and apoB disagree
For most people, LDL cholesterol and apoB rise and fall together, so LDL is a good enough guide. But in some people they point in different directions. This is called discordance.
It happens most often with insulin resistance. When triglycerides are high, LDL particles tend to become smaller and carry less cholesterol each. You can then have a “normal” LDL cholesterol but a high number of particles. Think of it as the same amount of cargo spread over many more small trucks. More trucks on the road means more chances of a crash.
- Fewer, larger LDL particles
- Normal triglycerides
- Risk is roughly what LDL suggests
- Many small, cholesterol-poor particles
- High triglycerides, low HDL, belly fat
- Risk is higher than LDL suggests
Illustrative examples. In studies of discordant results, heart risk tracks particle number (apoB) more closely than LDL cholesterol.
This pattern of high triglycerides, low HDL and many small LDL particles is especially common in South Asians, who tend to develop insulin resistance at a lower body weight. It is also common in people taking statins: statins lower LDL cholesterol a little more than they lower particle number, so some treated people still have more particles left than their LDL suggests. In both cases, apoB can show risk that a standard panel misses.
A large meta-analysis compared the three main measures directly. For the same statistical step up in each, apoB predicted heart risk most strongly.
Increase in heart disease risk per standard-deviation rise in each marker
Sniderman et al., Circ Cardiovasc Qual Outcomes 2011 (12 studies, about 234,000 people).
Healthy apoB levels
The 2019 European (ESC/EAS) guideline gives apoB targets that match its LDL targets for each risk level. The US 2018 guideline lists an apoB of 130 mg/dL or more as a “risk-enhancing factor” that can tip the decision toward treatment.
| Your risk level | ApoB goal | Matching LDL goal |
|---|---|---|
| Moderate | under 100 mg/dL | under 100 mg/dL (2.6 mmol/L) |
| High (for example, long-standing diabetes or familial hypercholesterolemia) | under 80 mg/dL | under 70 mg/dL (1.8 mmol/L) |
| Very high (for example, previous heart attack or stroke) | under 65 mg/dL | under 55 mg/dL (1.4 mmol/L) |
Mach et al., 2019 ESC/EAS guidelines. ApoB is reported in mg/dL or g/L (100 mg/dL = 1.0 g/L).
Not sure which group you are in? Read LDL cholesterol explained for how doctors judge risk, and diabetes and heart health if you have diabetes.
When to ask for an apoB test
The European guideline recommends apoB for risk assessment especially in people whose LDL result may be misleading. Consider asking about it if any of these apply:
- Triglycerides above about 150 mg/dL (1.7 mmol/L)
- Type 2 diabetes, prediabetes or insulin resistance
- Obesity, a large waist or metabolic syndrome
- Very low LDL cholesterol on treatment, where calculated LDL is less accurate
- Heart disease in yourself or close family despite “normal” cholesterol
Getting the test
Cost: apoB is an inexpensive, widely available test at larger labs in India, the US and the UK, often priced similar to or a little above a basic lipid panel. In the UK it is not part of routine NHS checks, so you may need to ask. Prices vary, so check with your lab or insurer.
How to lower apoB
Anything that lowers LDL lowers apoB: less saturated fat, more soluble fiber, healthy weight and, when needed, statins and other medicines. Because apoB also counts triglyceride-rich particles, cutting sugar, refined carbs and alcohol helps too. See how to lower LDL cholesterol and triglycerides explained.
Discuss results with your doctor. ApoB is one part of your risk. Decisions about medicine depend on your age, blood pressure, blood sugar, smoking and family history too.
MythIf my LDL is normal, my cholesterol risk is normal.
FactNot always. With high triglycerides or insulin resistance, you can have a normal LDL but a high number of particles. ApoB reveals this.
Common questions
Is apoB the same as LDL particle number (LDL-P)?
They are related. LDL-P is measured by a different method (NMR) and counts only LDL particles. ApoB counts all atherogenic particles and is more standardized and cheaper.
Does apoB include Lp(a)?
Yes, each Lp(a) particle carries one apoB. But Lp(a) particles are usually few in number, so a high Lp(a) can hide inside a normal apoB. Lp(a) needs its own test, done once in adulthood.
Do I need to fast for apoB?
No. ApoB changes very little after meals, which is another advantage over calculated LDL.
Should apoB replace LDL on my report?
Not necessarily. Most guidelines still use LDL as the main target and apoB as an extra check, especially in the situations listed above.
- ApoB counts every plaque-causing particle, one apoB per particle.
- With insulin resistance or high triglycerides, apoB can be high while LDL looks normal.
- ESC/EAS targets are under 100, 80 or 65 mg/dL depending on risk.
- It is a simple, non-fasting test worth asking about if you have metabolic risk factors.
- Next: LDL vs ApoB vs Non-HDL: Which Number Matters Most?.
Sources
- Sniderman AD, Thanassoulis G, Glavinovic T, et al. Apolipoprotein B particles and cardiovascular disease: a narrative review. JAMA Cardiol. 2019;4(12):1287–1295.
- Sniderman AD, Williams K, Contois JH, et al. A meta-analysis of low-density lipoprotein cholesterol, non-high-density lipoprotein cholesterol, and apolipoprotein B as markers of cardiovascular risk. Circ Cardiovasc Qual Outcomes. 2011;4(3):337–345.
- Mach F, Baigent C, Catapano AL, et al. 2019 ESC/EAS Guidelines for the management of dyslipidaemias: lipid modification to reduce cardiovascular risk. Eur Heart J. 2020;41(1):111–188.
- Grundy SM, Stone NJ, Bailey AL, et al. 2018 AHA/ACC/AACVPR/AAPA/ABC/ACPM/ADA/AGS/APhA/ASPC/NLA/PCNA Guideline on the Management of Blood Cholesterol. Circulation. 2019;139(25):e1082–e1143.
- Ference BA, Ginsberg HN, Graham I, et al. Low-density lipoproteins cause atherosclerotic cardiovascular disease. 1. Evidence from genetic, epidemiologic, and clinical studies. A consensus statement from the European Atherosclerosis Society Consensus Panel. Eur Heart J. 2017;38(32):2459–2472.
- Emerging Risk Factors Collaboration. Major lipids, apolipoproteins, and risk of vascular disease. JAMA. 2009;302(18):1993–2000.
This article is for general education and is not a substitute for advice from your own doctor or healthcare team.