Total Cholesterol / HDL Ratio
Your total cholesterol divided by your HDL ("good") cholesterol. Some labs print it as a single number that sums up your cholesterol balance.
AI-verified against cited sources. Awaiting expert reviewAlso called TC/HDL, TC:HDL, Chol/HDLLOINC 9830-1
Check your result
Type your result to see where it falls.
Nothing you type here leaves your browser.
What it is
This ratio is simple division: total cholesterol divided by HDL cholesterol, with both numbers in the same unit. A ratio of 4 means your total cholesterol is four times your HDL. It is also called the Castelli Risk Index I. Your lab works it out for you, and it has no unit. A lower ratio means less of your cholesterol sits outside the protective HDL particles.
Why it matters
A ratio can show something that total cholesterol alone hides. A higher total cholesterol can come mostly from protective HDL, while a normal total with low HDL gives a higher ratio. Clinicians have used the ratio for many years as a quick signpost for heart risk. Newer guidelines focus on LDL and non-HDL cholesterol instead, and Mayo Clinic notes that non-HDL may be more useful than the ratio. So the ratio works best as a supporting number.
If it’s low
A lower ratio is generally seen as favorable, because HDL makes up a larger share of your total cholesterol. The ratio cannot go below 1, since HDL is part of the total. A very low ratio usually reflects a high HDL, a low total cholesterol, or cholesterol-lowering treatment. A low ratio on its own does not usually need action, and your clinician can look at it with your other results.
Common causes
- A high HDL cholesterol
- A low total cholesterol, for example from cholesterol-lowering treatment or a low-fat diet
- Regular exercise, which raises HDL in some people
If it’s high
A higher ratio means total cholesterol is large compared with HDL. That can happen because LDL or other non-HDL cholesterol is high, because HDL is low, or both. Higher ratios are linked to a greater chance of heart disease over time. The ratio alone cannot show which part is driving it, so your clinician will look at the pieces.
Common causes
- Low HDL cholesterol, which often goes along with little physical activity, smoking, extra weight, type 2 diabetes or metabolic syndrome
- High LDL or non-HDL cholesterol
- High triglycerides, which often travel with low HDL
- Anabolic steroid use, which can lower HDL
- Family history of high cholesterol or low HDL, including inherited conditions
What can help
- Be active most days. Exercise raises HDL in some people
- If you smoke, ask your clinician about help quitting. Smoking is linked to lower HDL
- Work toward a healthy weight and eat a heart-healthy diet with less saturated fat, added sugar and refined carbohydrate
- Ask your clinician whether to follow this ratio, your LDL, or your non-HDL cholesterol over time
- Ask how your result fits your overall heart risk
Usual ranges
What labs print as the reference range, by who was tested. Ranges differ a little between labs, so the range on your own report is the one your result is judged against.
For adults: up to 4.9 ratio. Source: Quest Diagnostics (via Fullscript), Circulation (Nguyen, Ahmad, Navar), NHLBI / National Institutes of Health, ACC/AHA Task Force on Clinical Practice Guidelines, Labcorp.
- Adults (this one applies)up to 4.9 ratio
Sources: Quest Diagnostics (via Fullscript), Circulation (Nguyen, Ahmad, Navar), NHLBI / National Institutes of Health, ACC/AHA Task Force on Clinical Practice Guidelines, Labcorp
See Chol/HDL Ratio by age and sex, with the U.S. survey numbers where they exist.
How common is your level?
NHANES describes the US civilian, non-institutionalized population, not a 'healthy' reference group. People with disease, on medication, fasting or not (except fasting-subsample markers), smokers and so on are all included. A percentile says where a value sits among Americans of that sex and age, not whether it is normal.
Use the left and right arrow keys to read each age. Shift moves five years.
Reference data derived from CDC/NCHS National Health and Nutrition Examination Survey (NHANES), cycles 2015-2016, 2017-March 2020 (pre-pandemic), August 2021-August 2023. Analysis by bloodtesttracker.com; not endorsed by CDC, NCHS or HHS.
Explore Chol/HDL Ratio by age and sex: every percentile as a table, with a download.
What can affect your result
- Anything that changes total cholesterol or HDL cholesterol changes the ratio
- Meals: HDL is not affected by fasting, and total cholesterol is on average about 8 mg/dL lower after eating, so fasting is usually not needed
- Physical activity, smoking, body weight and diet
- Diabetes, kidney disease and some medicines
- Rounding can make the ratio on your report differ slightly from the one you work out yourself
- Lab cutoffs differ, so compare your result with the range on your own report
- The ratio is calculated from total cholesterol and HDL cholesterol, so any error in either one carries into it.
- High levels of N-acetylcysteine (a medicine used for acetaminophen overdose), and the acetaminophen byproduct NAPQI at overdose levels, can make the total cholesterol part read falsely low on some assays.
- Acute illness, infection or inflammation can change cholesterol and HDL for a while. Labcorp suggests avoiding a full lipid panel for about three months after a heart attack.
- Pregnancy can raise cholesterol, which affects the total cholesterol part.
A few weeks to a few months. HDL changes slowly and modestly with exercise, weight change or quitting smoking.
When to talk to a clinician
Talk with a clinician if your ratio is above the range on your report (for example, 5.0 or higher on a Quest report), especially if you also have diabetes, high blood pressure, a family history of early heart disease, or you smoke. This number cannot tell you whether you have heart disease. If you have chest pain or pressure, trouble breathing, or signs of a stroke such as face drooping, arm weakness or trouble speaking, call 911 or your local emergency number.
Questions you could ask
- Should I follow this ratio, my non-HDL cholesterol or my LDL over time?
- Is my ratio high because my HDL is low, my total cholesterol is high, or both?
- Which cholesterol number do you use to track my heart risk?
- What changes would help most to raise my HDL or lower my non-HDL cholesterol?
- Is a low ratio explained by a high HDL or by my treatment?
Questions people ask
What is a good cholesterol ratio?
Lower is better. Quest labels a ratio below 5.0 as in range. There is no single universal cutoff, and US guidelines do not set a target for this ratio, so your clinician may focus on your LDL or non-HDL cholesterol instead. Check the range printed on your own report.
How is the cholesterol ratio calculated?
Divide your total cholesterol by your HDL cholesterol, using the same unit for both. For example, a total of 200 mg/dL and an HDL of 50 mg/dL gives a ratio of 4.0, often written as 4-to-1. The ratio has no unit, so it is the same number in mg/dL and mmol/L.
Is the ratio better than LDL or non-HDL cholesterol?
Mayo Clinic says many healthcare professionals now think non-HDL cholesterol may be more useful than the ratio. Either seems to predict heart risk better than total cholesterol or LDL alone. Current guidelines set goals for LDL and non-HDL cholesterol, not for the ratio.
Do I need to fast for this ratio?
Usually not. HDL is not affected by fasting, and total cholesterol changes only a little after eating. Follow the instructions your lab or clinician gives you, especially if triglycerides are measured on the same panel.
Why is the ratio on my report slightly different from my own math?
Small differences can come from rounding. If the gap is larger, check that you used the same unit for both numbers, for example mg/dL for total cholesterol and for HDL.
Show the science and sources
For clinicians and researchers
The ratio is total cholesterol divided by HDL-C (Castelli Risk Index I). Both terms share a unit, so it is dimensionless and numerically identical in mg/dL and mmol/L; LOINC separates a mass ratio (9830-1) from a molar ratio (32309-7). Because HDL-C is part of total cholesterol, the ratio is never below 1 and equals 1 + non-HDL-C/HDL-C. Labs compute it from two separately measured values, so it carries the analytic and biological variation of both. HDL-C is not affected by fasting, and total cholesterol falls by about 0.2 mmol/L (8 mg/dL) on average after habitual meals (EAS/EFLM 2016). A 2026 Circulation review of the 2026 ACC/AHA Dyslipidemia Guideline states that current guidelines do not use lipid ratios to guide therapy or risk assessment and that treatment decisions should rest on individual components such as LDL-C; NCEP ATP III and the 2018 ACC/AHA guideline also set no ratio target. Total and HDL cholesterol enter the PREVENT equations as separate inputs. Quest prints a reference of <5.0 for the calculated ratio on its lipid panel with ratios. Labcorp reports 'T. Chol/HDL Ratio' (unit 'ratio', LOINC 9830-1) on its lipid panel with total cholesterol:HDL ratio (221010). Mayo Clinic notes that many clinicians now regard non-HDL cholesterol as more useful than the ratio, and either as a better predictor than total or LDL cholesterol alone.
LOINC 9830-1 (primary), 32309-7. Specimen: calculated.
Sources
- Lipid Panel with Ratios, Quest Diagnostics (reference ranges as listed by Fullscript), Quest Diagnostics (via Fullscript)
- Lipid Panel With Total Cholesterol:HDL Ratio (test 221010), Labcorp
- Cholesterol ratio or non-HDL cholesterol: Which is most important? (read from a 2025 Internet Archive copy), Mayo Clinic
- Third Report of the National Cholesterol Education Program (NCEP) Expert Panel on Detection, Evaluation, and Treatment of High Blood Cholesterol in Adults (Adult Treatment Panel III): Executive Summary, NHLBI / National Institutes of Health (2001)
- Understanding the new dyslipidemia guidelines, Quest Diagnostics (2026)
- Fasting is not routinely required for determination of a lipid profile: clinical and laboratory implications including flagging at desirable concentration cutpoints. A joint consensus statement from the European Atherosclerosis Society and European Federation of Clinical Chemistry and Laboratory Medicine, European Heart Journal (joint EAS/EFLM statement, also in Clinical Chemistry) (2016)
- Dyslipidemia (Hyperlipidemia), Merck Manual Professional Edition
- Lipid Profile Testing and Interpretation (summarizes the 2026 ACC/AHA Dyslipidemia Guideline), Circulation (Nguyen, Ahmad, Navar) (2026)
- 2018 AHA/ACC/AACVPR/AAPA/ABC/ACPM/ADA/AGS/APhA/ASPC/NLA/PCNA Guideline on the Management of Blood Cholesterol: Executive Summary, ACC/AHA Task Force on Clinical Practice Guidelines (2019)
AI-verified against cited sources. Awaiting expert review. Last reviewed 2026-10-03. How we build and check these pages.