For decades, the higher your “good” cholesterol, the better. A growing body of evidence is quietly refuting that idea and raising questions your doctor may not have answered yet.

He had been proud of that number for years. Every time his annual bloodwork came back, his HDL, the “good” cholesterol, was well above the threshold that cardiovascular guidelines have long identified as protective. His doctor had nodded approvingly. His health app coded it green. He took it as evidence that he was doing something right.

What he did not know, and what many physicians have not yet had reason to explain, is that the relationship between HDL cholesterol and heart health is no longer considered straightforward. A growing body of evidence, from large Scandinavian cohorts, from Mendelian randomization studies that use genetics to isolate causation, and from failed clinical trials that tried and could not replicate HDL’s presumed protective effects, is steadily dismantling a cornerstone of standard lipid interpretation.

The evidence does not say that a low HDL is unimportant. It does say, with increasing confidence, that a very high HDL is not a reliable sign of cardiac protection, and for some people, it may be associated with elevated risk.

How HDL Earned Its “Good Cholesterol” Label

The classification of HDL as protective cholesterol is rooted in observational data that goes back decades. Population studies, notably the Framingham Heart Study, which began tracking cardiovascular health in a Massachusetts town in 1948, consistently found that people with lower HDL levels had higher rates of heart attack and stroke. The biological explanation was plausible: HDL particles were understood to perform reverse cholesterol transport, pulling cholesterol from arterial walls and carrying it back to the liver for disposal. Higher HDL, the thinking went, meant more efficient arterial housekeeping and less plaque.

This correlation was strong enough, and the mechanism compelling enough, that raising HDL became a clinical goal. The Framingham Risk Calculator, still widely used to estimate 10-year cardiovascular risk, assigns a bonus point when HDL rises above 60 mg/dL, effectively reducing a patient’s calculated risk score. A generation of physicians was trained to reassure patients with high HDL that they had an advantage.

When Clinical Trials Failed to Confirm the Theory

The first substantial challenge came not from observational data but from pharmacology. If raising HDL was genuinely protective, drugs that boosted it should have reduced heart attacks and deaths. They did not.

A class of drugs called CETP inhibitors, designed to raise HDL by blocking the protein that transfers cholesterol from HDL to other lipoproteins, produced some of the most expensive failures in cardiovascular drug development. Torcetrapib, the most prominent example, was abandoned after a large clinical trial found that it actually increased mortality despite substantially raising HDL. Niacin, a supplement long used to raise HDL, similarly failed to produce the expected cardiovascular benefit in rigorously designed trials when added to standard statin therapy.

These failures prompted a re-examination of the fundamental assumption. Researchers began asking whether HDL levels in blood were genuinely protective, or whether they were simply a marker correlated with other factors, such as diet quality, exercise, and genetics, that carried the actual protective effect.

The association between HDL and cardiovascular risk may follow a U-shaped curve: both extremely low and extremely high levels appear to carry elevated risk. The optimal range, where risk is lowest, sits in the middle.

The U-Shaped Curve

The most direct challenge to the “higher is better” framework came from large prospective cohort studies examining what actually happens to people with very high HDL levels over time.

A study published in the European Heart Journal drew on data from more than 116,000 participants in two long-running Copenhagen population studies. Researchers tracked deaths from any cause over the years of follow-up. The relationship between HDL levels and mortality was not linear; it was U-shaped. Both very low HDL and very high HDL were associated with elevated all-cause mortality compared to the intermediate range.

The HDL concentration associated with the lowest all-cause mortality was approximately 73 mg/dL in men and 93 mg/dL in women. Men with HDL above 116 mg/dL had a 36% higher risk of all-cause mortality than those in the optimal range. At HDL levels of 116 mg/dL or higher, the risk was more than double. Women showed a similar pattern at the upper extreme.

A subsequent systematic review and meta-analysis confirmed the finding across multiple cohorts, concluding that extremely high HDL levels were associated with a 15% increase in all-cause mortality risk compared to normal HDL levels. A 2022 study published in JAMA Cardiology found similar patterns in high-risk populations with existing coronary artery disease.

HDL cholesterol reference ranges (approximate):

Low (increased risk): below 40 mg/dL in men, below 50 mg/dL in women

Optimal range: roughly 60–90 mg/dL (risk of cardiovascular events is lowest here)

Potentially concerning: above 97 mg/dL in men, above 135 mg/dL in women (based on Copenhagen Heart Study data)

Note: individual risk assessment requires clinical evaluation; ranges are population-level estimates, not diagnostic thresholds.

What Genetics Has Added to the Picture

Mendelian randomization studies have provided some of the most analytically rigorous contributions to this debate. The technique uses naturally occurring genetic variants, essentially the randomization that happens at birth, to ask whether having genes associated with lifelong higher HDL actually protects against heart disease. If the association between HDL and lower cardiac risk were causal, people with the genetic predisposition to higher HDL should have fewer heart attacks.

In most such analyses, they do not. A review published in Cardiovascular Drugs and Therapy in 2026 synthesized this literature, concluding that genetic causes of high HDL cholesterol do not significantly reduce myocardial infarction risk. In fact, certain genetic variants associated with high HDL, including mutations in genes called SCARB1 and LAG3, appear to be associated with increased risk. A variant in a gene called HNF4A has been significantly associated with both high HDL and increased heart attack risk.

What genetics cannot easily explain is why some people with high HDL do well. The emerging understanding is that HDL is not a single entity. It is a diverse population of particles that vary in size, composition, and function. Measuring total HDL cholesterol in blood captures how much cholesterol is being carried around on HDL particles, but not how well those particles are working. A person with very high HDL may have particles that are poor at removing cholesterol from arterial walls. A person with moderately elevated HDL may have highly functional particles. Blood tests don’t distinguish between them.

What Has Not Changed

Several things remain firmly supported by the evidence and should not be read as unsettled by any of this.

Low HDL, below 40 mg/dL in men and 50 mg/dL in women, is still associated with elevated cardiovascular risk and is worth clinical attention. The question is not whether the lower end of the HDL scale matters; it clearly does. The question is whether more is always better once a person is already in or above the normal range.

LDL cholesterol, the “bad” cholesterol, remains a well-established causal risk factor for cardiovascular disease, with a far stronger and more consistent evidence base than HDL. The clinical case for managing LDL, particularly through lifestyle modification and statins where indicated, is not weakened by any of the HDL findings.

The lifestyle behaviors associated with higher HDL, regular aerobic exercise, not smoking, maintaining a healthy weight, and eating a diet rich in unsaturated fats remain independently beneficial. Their benefit does not depend on HDL as the mechanism. Exercise, in particular, has cardiovascular effects that operate through many pathways simultaneously.

What This Means for Patients Today

For most people, HDL levels in the commonly reported range, somewhere between 50 and 90 mg/dL, carry no cause for alarm or special action in either direction. The HDL paradox is primarily relevant for two groups: people with very high HDL, above roughly 97 mg/dL in men or 135 mg/dL in women, for whom the new evidence warrants a conversation with their physician about the full lipid picture; and patients who have been led to believe that a high HDL effectively offsets other cardiovascular risk factors. It does not do that reliably.

The clinical implications are still being worked out. The Framingham Risk Calculator has not been formally revised to account for the U-shaped relationship, and most standard lipid panels continue to present HDL without any flag for unusually high values. Those updates may come as the evidence continues to consolidate. For now, the most useful thing an informed patient can do is treat a very high HDL reading not as a prize but as a data point to discuss, one piece of a cardiovascular risk profile that includes LDL, triglycerides, blood pressure, family history, and the full picture of lifestyle habits.

Bottom Line

Evidence strength: Moderate — large prospective cohort studies and Mendelian randomization analyses; clinical guidelines not yet formally revised

The long-standing view that higher HDL (“good”) cholesterol is invariably protective is no longer well supported by the evidence. Multiple large studies indicate a U-shaped relationship between HDL and cardiovascular risk, with both very low and very high levels associated with elevated risk. The range associated with the lowest mortality appears to be roughly 60–95 mg/dL. Clinical trials of HDL-raising drugs have not produced the cardiovascular benefits the HDL hypothesis predicted. Genetic studies suggest that a lifelong tendency toward higher HDL does not independently protect against heart attack.

For most people, HDL in the typical reported range is not a concern. But a very high HDL reading, above approximately 97 mg/dL in men or 135 mg/dL in women, is worth discussing with your physician, particularly if you have other cardiovascular risk factors. A high HDL does not reliably offset elevated LDL, high blood pressure, or other established risk factors. Managing those risks through lifestyle and, where appropriate, medication remains the better-supported strategy for protecting long-term heart health.