Atherogenic Index: cardiovascular risk ratio

What is the Atherogenic Index

The Atherogenic Index (also known as the Castelli Index or TC/HDL ratio) is a calculated marker obtained by dividing total cholesterol by HDL cholesterol. It shows the balance between "total" and "good" cholesterol and helps assess the risk of cardiovascular disease.

This marker complements individual lipid panel numbers by considering their mutual balance. A person with high total cholesterol but very high HDL may have a good atherogenic index — and vice versa.

Reference Range

The recommended atherogenic index is below 3.5. A lower value indicates a more favorable lipid balance and lower cardiovascular disease risk.

Some sources cite ideal ranges: below 4.5 for men, below 4.0 for women. However, the lower the ratio, the better. Laboratories may specify their own ranges — always refer to yours.

Why the Atherogenic Index May Be Elevated

An elevated index means total cholesterol is too high relative to HDL, or HDL is too low. Common causes: unhealthy diet (high in saturated fats, processed foods), low physical activity, obesity, smoking, and genetic predisposition (familial dyslipidemia).

Metabolic syndrome, type 2 diabetes, and hypothyroidism can also increase the atherogenic index. Some medications (e.g., beta-blockers, progestins) may lower HDL and worsen the ratio.

Why the Atherogenic Index May Be Low

A low atherogenic index is generally a positive sign — indicating good lipid balance and lower cardiovascular risk. Regular physical activity (especially aerobic exercise) raises HDL cholesterol and improves the index.

A diet rich in omega-3 fatty acids (fatty fish, walnuts, flaxseeds) can also contribute to a low index. Genetics also play an important role — some people naturally have high HDL levels.

What to Do Next

If the atherogenic index exceeds 3.5, first review the full lipid panel: total cholesterol, LDL, HDL, and triglycerides. Your doctor will assess overall cardiovascular risk, considering age, blood pressure, smoking, diabetes, and family history.

Lifestyle changes — a heart-healthy diet, regular physical activity, smoking cessation, and weight normalization — are the first-line strategy for improving the index. This is a topic to discuss with your doctor.

Monitoring Over Time

The atherogenic index is especially useful for tracking trends. If you change your diet or start exercising, repeat the lipid panel after 3–6 months and compare the ratio. QbiLabs automatically calculates and displays this index on your data chart.

Regular monitoring helps you see whether lifestyle changes are producing results and motivates you to continue healthy habits.

Questions for Your Doctor

1. What is my overall cardiovascular risk profile, considering the atherogenic index? 2. Are lifestyle changes sufficient, or would medication therapy be needed? 3. How often should I repeat the lipid panel? 4. Do my other markers (triglycerides, LDL) also indicate increased risk?