VLDL-C Laboratory Measurement and Calculation
VLDL-C (very-low-density lipoprotein cholesterol) is not directly measured in routine clinical practice but is calculated from the standard lipid panel using the triglyceride value.
How VLDL-C is Obtained
The standard method for determining VLDL-C is calculation using the Friedewald equation component: VLDL-C = triglycerides ÷ 5 (when values are in mg/dL). 1 This calculation is embedded within the widely-used Friedewald equation for estimating LDL-C: LDL-C = total cholesterol − HDL-C − (triglycerides/5). 1
Standard Lipid Panel Components
The routine fasting lipid panel directly measures only three values: 1
- Total cholesterol (directly measured)
- HDL cholesterol (directly measured)
- Triglycerides (directly measured)
VLDL-C is then calculated as triglycerides ÷ 5, based on the principle that VLDL particles contain approximately 20% cholesterol and 80% triglycerides by weight. 2, 3, 4
Alternative Calculation Methods
The Lipid Research Clinics formula suggests VLDL-C = triglycerides × 0.16 may provide more accurate estimates, particularly for triglyceride levels in the normal range. 2
For elevated triglycerides, the 0.20 multiplier (equivalent to dividing by 5) remains reasonably accurate up to triglyceride levels of 4,000 mg/dL, though precision decreases at triglyceride values exceeding 10,000 mg/dL. 3
The Martin-Hopkins method and newer NHLBI equations provide more accurate VLDL-C and LDL-C calculations, especially when triglycerides are elevated or LDL-C is very low. 1
Clinical Context
VLDL is the chief carrier of triglycerides in plasma, and VLDL-C represents the cholesterol content of these triglyceride-rich particles. 1 VLDL-C is atherogenic and contributes to cardiovascular risk. 1
Non-HDL-C (calculated as total cholesterol minus HDL-C) represents the sum of LDL-C plus VLDL-C and captures all atherogenic lipoproteins. 1 Non-HDL-C is increasingly recognized as a superior risk marker compared to LDL-C alone, particularly in patients with elevated triglycerides. 1
When the Friedewald Calculation Fails
The Friedewald equation becomes inaccurate when: 1
- Triglycerides exceed 400 mg/dL (some sources suggest 500 mg/dL as the cutoff)
- Non-fasting samples are used (triglycerides will be falsely elevated by 20-30 mg/dL, causing VLDL-C overestimation by 4-6 mg/dL) 1
- Type III dyslipidemia is present (abnormal VLDL remnants with higher cholesterol content) 1
In these situations, direct LDL-C measurement should be performed rather than relying on calculated values. 1, 5
Common Pitfalls
Do not confuse VLDL-C with triglycerides: VLDL-C represents only the cholesterol component (approximately 20%) of VLDL particles, while triglycerides comprise 80-95% of VLDL content. 6, 7
The Friedewald equation underestimates LDL-C by 4-6 mg/dL when applied to non-fasting samples because elevated postprandial triglycerides falsely inflate the VLDL-C estimate. 1
Direct LDL-C measurement is not clinically equivalent to calculated LDL-C: differences exceeding 15-20 mg/dL occur in 25-33% of patients, which can affect treatment decisions. 5
VLDL-C levels are not routinely reported separately on standard lipid panels; clinicians must calculate it manually if needed (triglycerides ÷ 5) or recognize it as the component subtracted in the Friedewald LDL-C calculation. 1, 2