The chiolesterol ratio commonly refers to the ratio that you obtain by dividing your total cholesterol with your high-density lipoprotein (HDL, or "good") cholesterol. It is used by the medical community to predict your risk of developing heart disease.
For example, if your total cholesterol is 200 milligrams per deciliter (mg/dL) or 5.2 millimoles per liter (mmol/L) and your HDL cholesterol is 50 mg/dL or 1.3 mmol/L, your cholesterol ratio is 4-to-1. For most people, the goal is to keep the total cholesterol to HDL cholesterol ratio below 5:1 with the ideal being below 3.5:1.
Cholesterol are not very soluble in water and therefore needs some assistance to travel throughout the blood stream. HDL (high density lipoprotein), helps form packets of cholesterol, move them through the blood to the liver where they are removed. HDL levels have an inverse relationship with coronary heart disease. The higher the HDL level the lower the risk of heart disease.
A high total cholesterol number can be due to either a high HDL number or a high LDL number or both. If it is high because of a high HDL number, your health is not necessarily in danger. However, if it is high because your LDL cholesterol level is high, your health is at risk. This ratio becomes high when the total cholesterol increases and HDL cholesterol decreases. Low ratio indicates lower risk of heart attack, while high ratio indicates higher risk.
Another ratio that is gaining prominence is the LDL/HDL ratio and it is found by diving LDL cholesterol by HDL cholesterol values. A ratio between 3.3 and 4.4 is considered low risk while a ratio between 4.4 and 7.1 is considered average risk. Between 7.1 and 11.0 is considered moderate risk while anything above 11 is considered high risk.
In the past, the cholesterol ratio (total cholesterol/HDL) was thought to be more important than individual levels of HDL cholesterol and LDL cholesterol. But now the medical community is divided on this.
Calculating your cholesterol ratio may provide useful information about your heart disease risk, but it isn't useful for deciding what treatment you should have to reduce your heart disease risk. It is now generally believed that your total cholesterol and low-density lipoprotein (LDL, or "bad") cholesterol levels are more useful in guiding treatment decisions than is your cholesterol ratio.
The American Heart Association recommends using the absolute numbers for total blood cholesterol and HDL cholesterol instead of cholesterol ratio. They believe that the absolute cholesterol numbers are more useful to plan treatment than this ratio.