A single number that captures lipid balance.
Source: Castelli, Am J Med 1986 — used in Framingham analyses.
What does the cholesterol ratio mean?
The total cholesterol to HDL ratio is calculated by dividing your total cholesterol by your HDL (high-density lipoprotein, or "good cholesterol"). It captures the balance between cholesterol being deposited into arterial walls (driven by LDL and VLDL, which contribute to total cholesterol) and cholesterol being removed from arterial walls and transported to the liver for excretion (driven by HDL).
Dr William Castelli of the Framingham Heart Study demonstrated in 1986 that this ratio was among the strongest predictors of coronary artery disease in the study population. The key insight is that a person with moderately elevated total cholesterol but very high HDL can have a lower cardiovascular risk than someone with lower total cholesterol but very low HDL.
HDL is raised by aerobic exercise, smoking cessation, and replacing saturated fats with unsaturated fats. Alcohol raises HDL modestly but its net effect on cardiovascular risk is debated. Total cholesterol is lowered by reducing saturated fat intake, increasing soluble fibre, and statin therapy. The ratio responds to both components and gives a quick summary of your lipid profile direction.
Note that the ratio is a screening tool, it does not replace a full lipid panel or a cardiovascular risk score. People with the same ratio can have very different absolute risks depending on their total cholesterol and HDL levels.
Reference ranges
| Risk category | Ratio (both sexes) |
|---|---|
| Optimal / very low risk | < 3.0 |
| Good | 3.0 – 3.5 |
| Average risk | 3.5 – 5.0 |
| Moderate risk | 5.0 – 6.0 |
| High risk | > 6.0 |
When should you see a doctor?
A ratio above 5.0 is worth discussing with your doctor, particularly if combined with other risk factors such as high blood pressure, diabetes, smoking, or family history of heart disease. Even a ratio in the "average" range may warrant treatment in someone with established cardiovascular disease or diabetes. Your doctor will interpret the ratio in the context of your full cardiovascular risk profile.