About

High-Density Lipoprotein (HDL) acts as a scavenger in the bloodstream, removing excess cholesterol and transporting it to the liver for excretion. Medical reports report these values in varying units depending on the laboratory location. The United States typically utilizes mg/dL, while Canada and Europe favor mmol/L. Misinterpreting these units leads to incorrect risk assessment.

This tool normalizes lipid data using the standard molar mass of cholesterol (386.65 g/mol). Accuracy is vital here because the threshold for cardiovascular protection differs significantly between men and women. A value considered borderline for a male patient may indicate high risk for a female patient. This utility applies NCEP ATP III guidelines to categorize results and computes the Total/HDL ratio, a derived metric often cited as a superior predictor of ischemic heart disease than isolated values.

Formulas

The conversion between molar concentration and mass concentration relies on the molecular weight of cholesterol.

C_mmol/L = C_mg/dL38.67

To assess risk using the Cholesterol Ratio:

Ratio = Total CholesterolHDL

Reference Data

Classification	Range (mg/dL)	Range (mmol/L)	Clinical Interpretation
Low (Men)	< 40	< 1.03	Major risk factor for heart disease.
Low (Women)	< 50	< 1.29	Major risk factor for heart disease.
Borderline (Men)	40 - 59	1.03 - 1.55	Intermediate protection.
Borderline (Women)	50 - 59	1.29 - 1.55	Intermediate protection.
Optimal / High	≥ 60	≥ 1.55	Considered protective against heart disease.

Frequently Asked Questions

Females typically have higher baseline HDL levels due to the effects of estrogen, which increases the production of ApoA-I, a major protein component of HDL. Consequently, the threshold for "low" HDL is set higher (< 50 mg/dL) for women compared to men (< 40 mg/dL) to reflect equivalent cardiovascular risk.

According to the American Heart Association, a ratio below 5:1 is the standard target for general health. A ratio below 3.5:1 is considered optimal and indicates a significantly lower risk of developing cardiovascular issues.

While HDL is generally "good", recent studies suggest a U-shaped curve for mortality. Extremely high levels (exceeding 90-100 mg/dL or 2.3-2.6 mmol/L) may be associated with genetic variants that do not necessarily confer added protection and could, in rare cases, be linked to adverse outcomes. Consult a lipidologist for values exceeding these upper limits.

You cannot use this specific tool for triglycerides. Triglycerides have a different molecular weight. The conversion factor for cholesterol is 38.67, whereas for triglycerides it is approximately 88.57. Using the wrong factor will result in a roughly 50% error.