HDL cholesterol is often referred to as the "good" cholesterol because it helps remove cholesterol from your arteries. According to the Cleveland Clinic, a healthy HDL level is above 60 mg/dL. However, the Mayo Clinic notes that people who naturally have extremely high HDL levels above 100 mg/dL (2.5mmol/L) appear to be at higher risk of heart disease. WebMD also states that HDL cholesterol levels less than 40 mg/dL are low and not so good. Therefore, it is important to maintain a healthy HDL level, but extremely high levels may not necessarily be beneficial.