Causes of high cholesterol include a poor diet, being overweight, low activity level, being older, certain diseases and medications, a family history of high cholesterol and being a smoker, according to WebMD. There are three different cholesterol numbers: high-density lipoprotein, or HDL, low-density lipoprotein, or LDL, and total cholesterol. While LDL and total cholesterol should be low, HDL is known as "good" cholesterol and should be high.
According to Mayo Clinic, total cholesterol should be below 200 milligrams of cholesterol per deciliter of blood, LDL should be below 70 milligrams of cholesterol per deciliter of blood and HDL should be above 60 milligrams of cholesterol per deciliter of blood. A diet high in saturated and trans fats can contribute to high LDL cholesterol. Foods high in these fats include meats, full-fat dairy products, fried foods and packaged goods.
At the age of 20, people's cholesterol levels begin to rise, but that rise is different for males and females. For males, cholesterol rises until age 50 and then tends to remain steady. Cholesterol levels found in females throughout the child-bearing years are usually lower than the levels found in males. However, once menopause is reached, cholesterol levels in females tend to rapidly rise to the levels found in men, according to WebMD.