HDL cholesterol under 40 mg/dL

ATP III's own words: "Low HDL cholesterol is a strong independent predictor of CHD." It sits in the panel's Table 3 of major risk factors alongside cigarette smoking, hypertension, a family history of premature heart disease and age, and the count of those factors is what sets the LDL goal. The line moved from 35 to 40 mg/dL in 2001 because 40 "is a better measure of a depressed HDL." ATP III also lists what usually drives the number down: the insulin-resistance cluster (high triglycerides, overweight, physical inactivity, type 2 diabetes), cigarette smoking, a diet over 60 percent carbohydrate, and drugs including beta-blockers, anabolic steroids and progestational agents.

What no guideline asks you to do. ATP III "does not specify a goal for HDL raising," and nothing since has. The 2026 ACC/AHA dyslipidemia guideline, which retired the 2018 cholesterol guideline in March 2026, states every treatment target as LDL cholesterol and non-HDL cholesterol. On drugs it is explicit: fibrates and niacin are not recommended for routine use "due to lack of proven reductions in ASCVD events when added to statin therapy," and niacin "should generally be avoided due to poor tolerability and adverse effects." ATP III's 2001 hope that raising HDL with drugs would cut risk predates the trials that tested it, and the current guideline has closed that door.

What the bodies do ask. ATP III sets the order: reach the LDL goal first, then, if the metabolic syndrome is present, shift to weight reduction and physical activity, and if triglycerides run 200 to 499 mg/dL, treat non-HDL cholesterol as the secondary target. The 2026 guideline still feeds your HDL into risk estimation (it is an input to the PREVENT equations, alongside total cholesterol, blood pressure, diabetes, tobacco use and kidney function) and describes low HDL as one feature of cardiovascular-kidney-metabolic syndrome rather than a stand-alone enhancer. Its physical activity section reports "a tendency toward higher HDL-C, lower TG, and less consistently lower LDL-C," with a meta-analysis of 148 trials finding an HDL rise of 2.11 mg/dL, and it prescribes at least 150 minutes a week of moderate aerobic activity plus resistance training on two or more days.

Retesting. The 2026 guideline recommends a lipid profile from age 19 "at least every 5 years," more often with additional risk factors, and says nonfasting samples can be used for most people. ATP III adds one rule for a nonfasting draw: a total cholesterol of 200 or higher or an HDL under 40 means a full fasting lipoprotein profile is needed next.

The same number as a metabolic syndrome criterion. Under 40 is also one of five criteria for the metabolic syndrome, and it is the only one drawn differently for men and women. ATP III's Table 8 sets the five: waist circumference over 102 cm (40 inches) in men or 88 cm (35 inches) in women, triglycerides of 150 mg/dL or higher, HDL under 40 in men or under 50 in women, blood pressure of 130/85 or higher, and an elevated fasting glucose. The rule: "the diagnosis of the metabolic syndrome is made when three or more of the risk determinants shown in Table 8 are present." The 2018 AHA/ACC cholesterol guideline printed the same HDL cutoffs and the same "any 3 of the following 5" rule and called the cluster "associated with an increased risk of ASCVD, diabetes mellitus, and all-cause death." The 2019 primary prevention guideline printed the same HDL cutoffs. None of the four documents explains why the women's line sits 10 mg/dL higher; they print the numbers and stop.

What changed in 2026. The 2026 ACC/AHA dyslipidemia guideline retired the 2018 guideline and no longer lists the metabolic syndrome or a numeric low HDL among its risk enhancers. It folds them into "cardiovascular-kidney-metabolic (CKM) syndrome," whose definition names "dyslipidemia (high serum TG and low serum high-density lipoprotein cholesterol [HDL-C] concentrations)" without a cutoff. So an HDL under 40 or 50 now counts by describing a pattern rather than by crossing a line, and the pattern is what the guideline treats: "The typical lipid profile of individuals with obesity often includes elevated TG, reduced HDL-C, and increased small cholesterol-depleted LDL particles. In the setting of obesity and CKM risk factors, non–HDL-C and apoB levels will more accurately reflect atherogenic risk than LDL-C." If your HDL is in this band and your triglycerides are up, the number your clinician should be steering by is non-HDL cholesterol or apoB, not LDL alone.

What the bodies say to do. ATP III: "First-line therapies for all lipid and nonlipid risk factors associated with the metabolic syndrome are weight reduction and increased physical activity." The 2018 guideline said lifestyle therapies are "particularly indicated" for this cluster. The 2026 guideline's dose is at least 150 minutes of moderate or 75 to 150 minutes of vigorous aerobic activity a week plus resistance exercise on two or more days, and it reports a "tendency toward higher HDL-C" with training. No body recommends a drug for the HDL number itself.