Low HDL cholesterol: what it means for your heart and what you can do

HDL stands for high density lipoprotein. HEART UK explains that lipoproteins are little parcels of fats and protein that transport fats around the body in the blood. HDL contains a lot of protein and relatively little fat, which makes it dense. It is one of five main types of lipoprotein.

It is often called good cholesterol. HEART UK points out that it is not the cholesterol itself that is protective but the HDL lipoprotein as a whole. It has three main effects: it removes excess cholesterol from blood vessels and other tissues and returns it to the liver to be recycled or removed, it has an anti-inflammatory effect that helps protect artery walls, and it has an anti-oxidant effect that helps protect cells and important chemicals in the blood.

The NHS explains that a cholesterol test can measure total cholesterol, HDL and non-HDL cholesterol. For healthy adults it gives a guide to healthy levels of HDL above 1.0 mmol/L for men or above 1.2 mmol/L for women, with total cholesterol below 5 mmol/L and non-HDL below 4 mmol/L. HEART UK gives the same figures and notes that HDL levels in boys fall after puberty and stay lower throughout life, which is why the thresholds differ.

The NHS stresses that what is a good target for you depends on things like your age, whether you have health conditions and your risk of cardiovascular disease, and that the figures are a guide for healthy adults. Illness, some medicines or a recent baby can make your levels lower or higher. It also says it makes little difference whether you have eaten before the test.

HEART UK adds a note of caution about the idea that more is always better. More recent research has found that both too little and too much HDL cholesterol are associated with increased cardiovascular risk.

HEART UK describes low HDL most often as part of a pattern with high triglycerides. This unhealthy pattern can be inherited and often occurs in people who are very overweight, especially if they carry weight around their middle, who have type 2 diabetes or who have metabolic syndrome.

The NHS lists general lifestyle contributors to cholesterol problems, including eating fatty food, not exercising enough, being overweight, smoking and drinking alcohol, and notes that you are more likely to have high cholesterol if you are over 50, a man, have been through the menopause or are of South Asian or sub-Saharan African origin. It can also run in families.

Because several causes can overlap, it is useful to review your overall health rather than treating the HDL figure in isolation, and a GP may want to look at blood pressure and blood sugar as well.

The practical approach is to reduce overall cardiovascular risk rather than to chase the HDL number alone. The NHS says you can lower your cholesterol by eating healthily and getting more exercise, and that some people also need medicine.

HEART UK lists measures that help the related pattern of high triglycerides and low HDL: reaching a healthy weight and shape, regular physical activity of at least 150 minutes a week at moderate intensity, replacing saturated fats with unsaturated fats, choosing wholegrain foods, cutting added sugars, eating fruit, vegetables and fish, and keeping alcohol to no more than 14 units a week.

If your risk of heart attack or stroke is high, the NHS says statins are the most common medicine and are usually taken for life, with other tablets or injections available if statins do not work or cannot be taken. A GP decides this based on the whole risk picture, not on HDL alone.

Low HDL does not cause symptoms, so it is usually found through a cholesterol test arranged because of another risk factor, or through a private test. Discuss the result with your GP, especially if you also have high blood pressure, diabetes, a family history of early heart disease or high triglycerides.

Call 999 for symptoms of a heart attack or stroke whatever your cholesterol results show. Private cholesterol tests can be convenient but, as with NHS tests, the key is what is done with the result in the context of your overall risk.