ApoB: counting the particles that build plaque

Apolipoprotein B (ApoB) is the protein wrapped around every lipoprotein particle that can lodge in an artery wall: LDL, VLDL, IDL and Lp(a). Each of those particles carries exactly one ApoB molecule. So a blood ApoB level is, in effect, a particle count. It is reported in mg/dL in the US and in g/L in Europe (100 mg/dL is 1.0 g/L).

A standard lipid panel does not include it. LDL cholesterol measures the cholesterol cargo, not the number of carriers, and in people with high triglycerides, insulin resistance or obesity the two can drift apart: many small particles, each carrying less cholesterol. That is the case for ordering ApoB.

The guideline numbers

Two points about the table. These are treatment goals tied to a person's overall risk, not a reference range for healthy people. And neither guideline sets an "optimal" ApoB for someone at low risk. The very low targets you will see online, often 60 mg/dL or under for everyone, are an extrapolation from the trials and genetics below. It is a defensible argument, but it is an opinion about primary prevention, not a guideline.

What raises and lowers it

• Raises: inherited conditions such as familial hypercholesterolaemia, diets high in saturated fat, excess weight and insulin resistance, type 2 diabetes, an underactive thyroid, kidney disease with heavy protein loss, and some drugs.
• Lowers: statins, ezetimibe, PCSK9 inhibitors and other lipid drugs, weight loss, and replacing saturated with unsaturated fat.
• Barely changes with a meal. The EAS/EFLM consensus found ApoB is not affected by fasting status, which makes it easier to compare across draws than triglycerides.

What it predicts

The strongest evidence that particle number is what matters comes from genetics. In a 2019 Mendelian randomisation study in JAMA covering 654,783 people and 91,129 cases of coronary heart disease, gene variants that lowered triglycerides and gene variants that lowered LDL cholesterol gave the same reduction in risk per 10 mg/dL lower ApoB: an odds ratio of 0.771 and 0.773. Once ApoB was accounted for, neither triglycerides nor LDL cholesterol added anything. That is a lifelong, genetic exposure, so the size of the effect does not translate directly to a few years on a drug, but the direction is consistent with the statin trials.

This is why the 2019 European guideline says ApoB may be preferred over LDL cholesterol in people with high triglycerides, diabetes, obesity or very low LDL. It is also why the LDL and HDL page and the triglycerides page keep coming back to particles.

On GLP-1 drugs and weight loss

The pivotal semaglutide and tirzepatide trials report LDL cholesterol rather than ApoB on their labels. LDL fell modestly: 2.5% on semaglutide 2.4 mg against a 1.3% rise on placebo in STEP 1, and 7.1% on tirzepatide 15 mg against 1.7% on placebo in SURMOUNT-1. The bigger change is in triglycerides, which suggests fewer triglyceride-rich particles.

The clearest ApoB data so far is for retatrutide, which is investigational. A 2026 post hoc analysis of two phase 2 trials found placebo-adjusted ApoB falls of up to 21.4% in people with type 2 diabetes over 36 weeks and up to 24.2% in people without diabetes over 48 weeks. Post hoc, phase 2, and not yet tested against outcomes. The retatrutide page covers where that drug stands.

How to test

• A single blood draw. Fasting is not required, though many people pair it with a fasting lipid panel.
• Ask for it by name. It is not part of a standard lipid panel, and Peptide AI's panels do not include it (see below).
• ApoB varies less from draw to draw than triglycerides do, but one value is still one value. Repeat a surprising result before changing anything.
• Keep the lab constant where you can. The lab report guide explains why.

Where it sits in Peptide AI

ApoB is not one of the markers Peptide AI groups and scores. The markers printed next to it on most reports, LDL, HDL, total cholesterol and triglycerides, sit in the metabolic panel, and the longevity bloodwork guide puts ApoB in context with the others.

Tracking it in Peptide AI

The lipid markers around ApoB are read from a lab PDF or manual entry, scored as part of the metabolic panel and plotted against your dose timeline. Log the draw date, whether you fasted, and anything unusual in the days before, such as illness, a hard session or a dose step, so the next result is compared like with like. Bloodwork tracking shows the series next to the dose log, weight and side effects, and the panels page lists every marker the app groups. More markers are in the bloodwork guides.