For decades, assessing cholesterol risk has been built around a simple idea: Lower “bad” cholesterol, lower your chance of a heart attack. The test at the center of that approach measures how much low-density lipoprotein, or LDL cholesterol, is circulating in part of the blood. It has shaped everything from clinical guidelines to the widespread use of statins, medications that reduce LDL.

It works. Lowering LDL cholesterol reduces heart attacks, strokes, and early death. But it doesn’t tell the whole story.

The LDL cholesterol test measures the amount of cholesterol inside the low-density lipoprotein particles circulating in the bloodstream. Those LDL particles containing the cholesterol can get trapped in artery walls, forming plaques that can eventually block blood flow. As the test measures the amount of cholesterol being carried, not the number of LDL particles themselves, two people can have the same LDL cholesterol level but very different numbers of particles, and therefore different levels of risk.

That gap has pushed researchers toward a different way of measuring risk. Apolipoprotein B, or apoB, reflects the total number of cholesterol-carrying particles in the blood rather than how much cholesterol they contain. A growing body of research suggests it’s a more accurate way of identifying who is at risk and who’s not.

In March 2026, the American Heart Association and American College of Cardiology recognized this. Their updated cholesterol guidelines acknowledged apoB as a potentially more precise marker, in line with earlier European recommendations. But they stopped short of recommending apoB as the primary method for testing.

“They review the evidence and rank apoB as superior, but the actual rules of the road continue to prioritize LDL,” says Allan Sniderman, a cardiologist at McGill University.

Sniderman was an author on a 2026 JAMA modeling study that analyzed lifetime outcomes for around 250,000 US adults eligible for statin treatment. Comparing LDL cholesterol, non-HDL cholesterol, and apoB, the study found that using apoB to guide treatment decisions would prevent more heart attacks and strokes than current approaches, while remaining cost-effective.

ApoB testing can be done through standard blood tests. So why has it not filtered into routine care? Not even in Europe, where the guidelines have reflected its usefulness for years.

Part of the answer is inertia. For decades, LDL cholesterol has been both a scientific breakthrough and a public health success story. It is simple, widely understood, and directly linked to treatments that work.

“For 50 years, LDL cholesterol was an amazing discovery,” Sniderman says. “It’s not that it isn’t a good marker. It is a good marker.”

Børge Nordestgaard, president of the European Atherosclerosis Society, agrees that LDL cholesterol remains central for a reason. “The evidence is immense; it’s beyond discussion,” he says. “Statins reduce heart attacks, strokes, and early death through LDL cholesterol lowering.”

That success helped shape a powerful narrative: LDL is “bad cholesterol,” and lowering it saves lives. But that simplicity has also limited how risk is understood.

“The result is patients and physicians know little or nothing about apoB,” Sniderman says.

More recent research suggests that the cholesterol picture is more complex, especially in people already taking statins. Previous studies led by Nordestgaard have shown that in treated patients, high levels of apolipoprotein B and non-HDL cholesterol remain associated with increased risk of heart attacks and mortality, while LDL cholesterol does not. ApoB, in particular, emerged as the most accurate marker.

For Kausik Ray, a cardiologist at Imperial College London, the challenge is not choosing one marker over another, but understanding what each one captures, and what it misses.

“We’re not interested in cholesterol for its own sake,” Ray says. “We’re trying to prevent heart attacks and strokes.”

Cholesterol enters artery walls through apoB-containing particles, but those particles are not all the same. LDL makes up most of them, but lipoprotein(a) and triglyceride-rich particles also play a role. ApoB captures the total number, but not their source.

“Having a very high apoB will pick up more people than just LDL,” Ray says. “But then what you do about that is another matter.”

An elevated apoB could be driven by different underlying problems—high LDL, insulin resistance, obesity, or genetic factors—and each may require a different intervention.

“If you only had apoB, you don’t know whether to focus on LDL-lowering or weight loss or glucose control,” Ray says.

That is where nuance comes in. ApoB may be a better overall signal of risk, but clinicians still need to understand what is driving it. “Because then you can personalize it,” Ray says.

That need for a more detailed picture is already pushing cholesterol testing beyond a single number. Both Ray and Nordestgaard point to lipoprotein(a), a genetically determined form of cholesterol that is rarely measured but can significantly increase risk.

“We’ve got a huge problem in the UK with less than 5 percent of the population being tested,” Ray says. “You only need to measure lipoprotein(a) once in your lifetime.”

Nordestgaard argues that if lipid testing were designed from scratch today, it would not center on a single measure at all.

“You would test your LDL cholesterol, your remnant cholesterol, and your lipoprotein(a),” he says. “You would make three parallel tests.”

The shift is not just about better markers, but earlier detection. Cardiovascular risk builds silently over decades, yet testing often begins only once symptoms or clear risk factors appear, e.g. being male and over 60.

“If you don’t look, you don’t know,” Ray says. “Typically, people in their twenties, thirties, forties are often not going to have things checked, because they feel fine.”

Instead, he says, care is often reactive, which has consequences for prevention.

Beyond apoB, researchers are beginning to explore even more granular ways of measuring risk. Large-scale examining the chemical molecules produced by the body’s metabolism, alongside genetic data, suggest that cardiovascular risk is shaped by a complex interplay of biological pathways, not a single biomarker.

One analysis, for example, found that combining metabolic and genetic information can improve risk prediction beyond traditional cholesterol measures, helping to explain why people with similar profiles can have very different outcomes.

The challenge is translating that complexity into clinical practice. More detailed testing brings higher costs, greater analytical burden, and the need for new evidence to guide treatment decisions.

For researchers, the direction of travel is clear. Medicine must move away from single-number diagnostics toward more layered, data-driven assessments of risk.

For now, apoB sits at the center of that transition: a better population-level measure than LDL cholesterol alone, but still only part of a broader picture.

“This whole concept of normal—we’ve got to get rid of that and explain to people there’s a continuum for all of these things,” Ray says. “There isn’t a black-and-white answer, unfortunately.”