What Causes Low HDL Cholesterol Levels?

While having low triglycerides and ​LDL cholesterol can have a positive effect on your heart health, having low levels of HDL cholesterol may count against you. That's because HDL is considered “good cholesterol."

HDL (high-density lipoprotein) plays an interesting role in that it actually removes LDL cholesterol (your "bad" cholesterol) from the walls of your arteries. This may protect your arteries from clogging up and causing conditions like a heart attack or stroke.

In fact, studies have shown that low HDL levels are linked to an increased risk of developing cardiovascular disease. This is especially true if other lipids, such as LDL cholesterol and triglycerides, in your blood are also high. Likewise, research suggests that high HDL levels are linked to a lower risk of cardiovascular disease.

It's important to understand that there is no direct causal relationship found between HDL levels and having a heart attack or stroke—hinting that other factors are at play, and a person's HDL level is one piece of the puzzle. 

Normal HDL cholesterol levels range between 40 and 60 milligrams per deciliter (mg/dL). However, doctors focus less on the actual HDL "number" and more on a person's entire heart health and how their individual HDL level fits into that picture.

For instance, let's say a person is overweight and smokes and is found to have a low HDL on a routine blood test. Instead of prescribing a medication to increase the HDL to a "normal" number, a doctor will focus on smoking cessation counseling, exercise, and weight loss—these measures can all effectively raise the HDL. In fact, you may be surprised to learn that there is no great scientific evidence out there to support the use of medication to raise a person's HDL level.

There are a number of conditions and lifestyle choices that play a role in lowering HDL levels. While these may not be a factor for you, think about these issues and discuss with your doctor:

• Uncontrolled diabetes: Having high blood glucose levels may contribute to lowering HDL cholesterol levels. It can also increase triglyceride and LDL levels. Getting your blood sugar under control may help get your HDL levels back within a healthy range. This can be done by modifying your lifestyle or taking medication to treat it.
• Smoking: The chemicals found in cigarettes can lower your HDL cholesterol. Quitting smoking can help increase your HDL, as well as prevent other chronic diseases, including cardiovascular disease.
• Sedentary lifestyle: Adding moderate exercise to your daily routine may help increase your HDL levels slightly. The American Heart Association recommends aerobic exercising 40 minutes daily three to four times weekly—examples include swimming, brisk walking, running, bicycling, and dancing. 
• Carry Excess Weight: Having excess weight can cause a number of health conditions, including a decrease in your HDL levels. If you are overweight or obese, losing weight can increase these levels and lower your risk of heart disease.

Your HDL level is important, but your doctor will likely focus less on the precise number and more on what it means. In other words, she will focus on interpreting your HDL level within the context of your risk factors for heart disease like your family history, weight, activity level, whether you smoke, and whether you have other medical conditions like high blood pressure or diabetes.

If your doctor tells you your HDL level is low, try not to be discouraged. Instead, focus your energy on getting healthier, whether that means losing weight if you are overweight or obese, stopping smoking, or getting outside for a jog. If you need help meeting these lifestyle goals, that's OK. Talk with your doctor—it may be a good time to see a nutritionist or even start a weight loss program.