HDL Cholesterol: Normal Values and What a Low HDL Means

Cholesterol does not dissolve in blood, so it travels packaged inside lipoproteins: spheres with a fatty core and a protein coat. HDL stands for high-density lipoprotein, the smallest and densest type. The test does not measure those particles themselves, but the amount of cholesterol inside them. That distinction matters more than it looks: the result tells you something about the cargo, not about the number of particles and not about how well they do their job.

HDL particles are the collection service of cholesterol transport. They take cholesterol up from cells around the body, including the foam cells in an early plaque in the artery wall, and deliver it to the liver, which disposes of it through the bile. This is called reverse cholesterol transport, and it is why a high HDL was seen as protective for decades.

In the Netherlands the result is reported in mmol/l. Unlike LDL, the laboratory prints only a lower limit here, no upper limit, and that lower limit differs by sex: 1.0 mmol/l for men and 1.2 mmol/l for women. The difference is physiological. Oestrogen gives women a higher average HDL, so the bar sits higher for them. The practical consequence: a value of 1.1 mmol/l is normal in a man and too low in a woman. Do not simply compare your number with your partner's.

One relationship you need to know in order to read the result: HDL moves inversely with triglycerides. A transfer protein swaps cholesterol out of the HDL particles in exchange for triglycerides from the fat-rich particles. The HDL particle ends up loaded with triglycerides, loses cholesterol and is cleared faster. Anyone with a lot of triglycerides in the blood is therefore left with a low HDL almost automatically. In practice a low HDL is rarely a stand-alone problem; it is usually the shadow of a raised triglyceride value and of the insulin resistance behind it.

You do not need to fast for an HDL test. HDL barely changes after a meal, unlike triglycerides.

Almost every page about HDL says the same thing: HDL is the good cholesterol, and the higher the better. Both halves of that sentence are wrong, which is exactly why this is the most important section on this page.

Higher is not always better. The relationship between HDL and all-cause mortality is not a straight line but a U. In two large Danish population studies, together more than 116,000 men and women, the lowest mortality sat at an HDL of roughly 1.9 mmol/l in men and roughly 2.4 mmol/l in women. Above that, the curve turns: men with an HDL of 3.0 mmol/l or more had roughly twice the mortality, women from 3.5 mmol/l upwards around one and a half times. An extremely high HDL is therefore not a certificate of health, and it deserves a conversation with your doctor rather than congratulations.

HDL is a gauge, not a dial. If a high HDL protects, then raising HDL ought to help. That has been tried extensively and it did not work. Drugs that inhibit the CETP transfer protein raised HDL by tens of percent and did not reduce heart attacks; the first in that class actually caused more deaths. Niacin raised HDL, but added no benefit on top of a statin and did add side effects. Genetic research points the same way: people who naturally carry a variant that raises HDL do not have a lower risk of myocardial infarction because of it, while that does hold for LDL-lowering variants.

What does that mean? That a low HDL is not a cause, but a signal. HDL is low because something else is going on: visceral fat, insulin resistance, smoking, too little movement, or high triglycerides. Those are the factors that carry the risk. Fixating on the HDL number means treating the thermometer instead of the fever.

So what do you do with it. Use HDL as context for the rest of your panel. A low HDL alongside high triglycerides and a raised fasting glucose together sketch a metabolic pattern that genuinely does carry risk. A low HDL also raises the cholesterol/HDL ratio, which is used in Dutch risk tables. But the values that predict risk most sharply are LDL, non-HDL cholesterol and ApoB, the number of risk-carrying particles. Your HDL says nothing about those.

And finally: there is no target value for HDL. Your doctor does not set an HDL goal the way they set one for LDL, because no treatment has been shown to lower your risk by raising HDL.

HDL is almost never measured on its own. It belongs in a lipid profile, together with total cholesterol, LDL and triglycerides, and that combination is exactly what makes the result interpretable.

You do not need to fast. HDL barely shifts after a meal, usually by less than a tenth of an mmol/l. Triglycerides are a different story, and because a non-fasting triglyceride value can inflate the calculated LDL, your doctor may still ask for a fasting repeat. For the HDL number itself the timing matters little.

Postpone the blood draw until a few weeks after an infection, an operation or a heart attack. The whole lipid profile dips temporarily at those times and paints a falsely favourable picture of your usual situation.

Testing makes sense during a periodic check of your cardiovascular risk, with a family history, with excess weight, diabetes or high blood pressure, when following a lifestyle change, and when you want to know what sits behind an earlier abnormal cholesterol result. If you find a low HDL, look first for causes beyond lifestyle: diabetes and insulin resistance, kidney or liver disease, heavy alcohol use, and medication. A TSH test also belongs with an unexpectedly abnormal lipid profile, because an underactive thyroid affects cholesterol. And always report the use of androgens or anabolic steroids: they lower HDL sharply.

The table below shows how HDL behaves in different groups and under different influences. These are directions, not cut-offs.

A single measurement is a snapshot. Have an abnormal result repeated before drawing conclusions from it, preferably at the same laboratory.