High cholesterol occurs when there is too much cholesterol — a fatty substance — in the blood. Cholesterol is essential for building cells and producing hormones, but having too much of it can lead to fatty deposits in the arteries. Over time, these deposits narrow the arteries and increase the risk of heart disease, stroke, and other circulatory problems. Because high cholesterol often causes no symptoms, it is usually detected through routine blood tests.

There are two main types of cholesterol: low-density lipoprotein (LDL), often called “bad” cholesterol, and high-density lipoprotein (HDL), known as “good” cholesterol. LDL contributes to plaque buildup in the arteries, while HDL helps remove excess cholesterol from the bloodstream. An imbalance between these two — high LDL and low HDL — increases cardiovascular risk.

Several factors contribute to high cholesterol. Diets high in saturated and trans fats, lack of physical activity, smoking, and being overweight are common causes. Genetics also play a significant role, meaning some people inherit a tendency to have high cholesterol even with a healthy lifestyle. Age and underlying conditions, such as diabetes or thyroid problems, can also affect cholesterol levels.