The categories
These come from the NCEP Adult Treatment Panel III executive summary, which remains the source of the familiar category labels, and from the 2005 AHA/NHLBI scientific statement that defines the metabolic syndrome criteria.
| Population | Category | HDL-C |
|---|---|---|
| Adults (ATP III) | Low, a major risk factor | Under 40 mg/dL |
| Adults (ATP III) | High, a negative risk factor | 60 mg/dL and above |
| Men (metabolic syndrome criterion) | Reduced HDL-C | Under 40 mg/dL |
| Women (metabolic syndrome criterion) | Reduced HDL-C | Under 50 mg/dL |
Two things follow that people often miss. ATP III's own low threshold is 40 mg/dL regardless of sex; the sex split appears only in the metabolic syndrome criteria, where the bar for women is 50. And "negative risk factor" at 60 and above has a specific technical meaning in ATP III: it subtracts a risk factor from the count, rather than describing a target you should be aiming at.
Why nobody treats HDL
Low HDL predicts cardiovascular events. That much is not in dispute and is why it sits in the risk calculators. The question the field asked next was the obvious one: if low HDL predicts events, does raising it prevent them? Two large trials answered, and both answers were no.
AIM-HIGH: raising HDL changed nothing
Published in the New England Journal of Medicine in December 2011, AIM-HIGH randomized 3,414 patients with established cardiovascular disease, all on simvastatin, to extended-release niacin or placebo. The niacin worked on the numbers exactly as intended. At two years it had raised median HDL from 35 to 42 mg/dL, lowered triglycerides from 164 to 122 mg/dL and lowered LDL from 74 to 62 mg/dL.
The primary endpoint occurred in 282 patients on niacin (16.4 percent) and 274 on placebo (16.2 percent), a hazard ratio of 1.02 with a 95 percent confidence interval of 0.87 to 1.21 and a P value of 0.79. The trial was stopped after a mean of three years for lack of efficacy. Every lipid number moved in the right direction and the event rate did not move at all.
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Torcetrapib: raising it a lot was worse
The ILLUMINATE trial, published in the same journal in November 2007, tested torcetrapib, a CETP inhibitor, in 15,067 patients at high cardiovascular risk, on top of atorvastatin. At twelve months it had raised HDL by 72.1 percent and lowered LDL by 24.9 percent. On the lipid panel it was the most effective drug anyone had built.
It was terminated early. Cardiovascular events rose, with a hazard ratio of 1.25 (95 percent CI 1.09 to 1.44, P=0.001), and death from any cause rose, hazard ratio 1.58 (95 percent CI 1.14 to 2.19, P=0.006).
Taken together, the two trials are why HDL is now read as a marker of something else, metabolic health, rather than as a dial to turn. A low HDL is a reason to look harder at triglycerides, weight, activity, smoking and glucose, all of which move HDL as a side effect of moving themselves.
Our HDL reference page lists each category with its source and effective date, cholesterol levels by age covers the rest of the panel, and the lab result lookup will place a specific number.
Frequently asked questions
What is a low HDL level?
Under 40 mg/dL, per NCEP ATP III, which classes it as a major risk factor for coronary heart disease. In the separate metabolic syndrome criteria from the 2005 AHA/NHLBI statement, the threshold is under 40 mg/dL for men and under 50 mg/dL for women.
Is a high HDL always good?
ATP III counts 60 mg/dL and above as a negative risk factor, meaning it subtracts one from your risk factor count. That is a scoring convention rather than a target, and the drug trials that raised HDL deliberately did not reduce events. HDL is best read as a marker of metabolic health rather than as a number to maximize.
Can I take a supplement or drug to raise HDL?
Nothing is prescribed for that purpose. Niacin raised HDL from 35 to 42 mg/dL in AIM-HIGH and produced an event rate of 16.4 percent versus 16.2 percent on placebo, and the trial was stopped for lack of efficacy. Torcetrapib raised HDL by 72.1 percent and was stopped early for increased cardiovascular events and deaths.
Why is the HDL threshold different for women?
Only in one place. ATP III's low-HDL threshold is 40 mg/dL for everyone. The sex-specific values, under 40 for men and under 50 for women, come from the 2005 AHA/NHLBI metabolic syndrome criteria, which is a different document answering a different question.
What actually raises HDL?
The things that improve metabolic health generally: physical activity, stopping smoking, and reducing triglycerides through weight and diet change. The reason to do them is their effect on cardiovascular risk overall. The HDL rise is a by-product, and on the trial evidence it is not the part doing the work.
When to talk with a clinician
Bring a low HDL up as part of the whole panel rather than on its own, particularly alongside triglycerides, waist circumference, blood pressure and glucose, because those five together are what the metabolic syndrome criteria are actually asking about. A single low HDL is a prompt to look at the pattern, not a number to chase.
