Maintaining a normal ratio between the HDL (good) cholesterol and total cholesterol levels is important for avoiding atherosclerosis, or stiffening of the arteries, according to MedicineNet. Dividing the total cholesterol number by the HDL number yields this ratio, and the higher the ratio, the higher the risk of heart attack.
Low levels of HDL cholesterol and high levels of total cholesterol both increase this ratio. Average ratios are approximately 4.5 as of 2015, but the healthiest averages are less than 4 and ideally less than 3, notes MedicineNet.
Another (and more expensive to obtain) way to look at cholesterol ratios is to find the quotient of the LDL (bad) cholesterol and the HDL (good) cholesterol. No matter what the ratio is, the best levels for LDL cholesterol are less than 100 (ideally, less than 80), no matter what the HDL total is. People who have other risk factors for heart disease, such as diabetes, high blood pressure, tobacco use or a genetic predilection, should keep their LDL levels as low as possible. Patients suffering from coronary artery disease and who have undergone stent implantation, bypass surgery or other surgical interventions should aim for LDL levels below 80, according to MedicineNet.