Testing for ‘Bad Cholesterol’ Doesn’t Tell the Whole Story

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.”