Does a cholesterol lab test require fasting?

From the Guidelines

Fasting is not required for a standard cholesterol lab test, as a nonfasting lipid profile provides acceptably accurate measures for risk calculation. According to the 2014 U.S. Department of Veterans Affairs and U.S. Department of Defense clinical practice guideline 1, a nonfasting lipid profile provides measures of total cholesterol and HDL-C levels that differ little from measures after a 9- to 12-hour fast.

The key points to consider are:

• Nonfasting LDL-C level may be 10% lower and triglyceride levels may be as much as 20% higher compared to fasting measures 1
• Lipid measures are necessary to enable risk calculation based only on measures of total cholesterol and HDL-C levels, and the small variance in LDL-C level is unlikely to affect classification of risk or therapeutic decisions 1
• If triglyceride levels are greater than 4.52 mmol/L (>400 mg/dL), the Friedewald equation commonly used to calculate LDL-C levels may not be accurate, and a nonfasting lipid profile may need to be remeasured after fasting 1

In terms of practical considerations, routine fasting lipid measures can burden patients and laboratories, as most patients do not come to clinic visits while fasting, and laboratories can be burdened by the large number of patients who present early in the morning after an overnight fast 1. Therefore, a nonfasting lipid profile is a reasonable and acceptable alternative to a fasting lipid profile for most patients.

From the Research

Cholesterol Lab Test Requirements

• A cholesterol lab test does not necessarily require fasting, as recent research suggests that nonfasting cholesterol measurements can predict outcomes at least as well as fasting cholesterol measurements 2, 3.
• Nonfasting lipid profiles have been shown to be superior to fasting in predicting cardiovascular risk, with minimal changes in lipid and lipoprotein levels in response to normal food intake 2.
• The maximal mean changes in lipid levels after a meal are not clinically significant, with changes of +0.3 mmol/L (26 mg/dL) for triglycerides, -0.2 mmol/L (8 mg/dL) for total cholesterol, and -0.2 mmol/L (8 mg/dL) for LDL cholesterol 2, 4.

Benefits of Nonfasting Cholesterol Measurement

• Nonfasting cholesterol measurement can simplify blood sampling in the laboratory and benefit patients by avoiding the inconvenience of fasting 2.
• Nonfasting measurement can also minimize the risk of hypoglycemia in individuals with diabetes 2, 5.
• Many countries are changing their guidelines to recommend nonfasting lipid profiles for cardiovascular risk prediction, simplifying blood sampling for patients, laboratories, and clinicians worldwide 2.

Clinical Implications

• The European Atherosclerosis Society and European Federation of Clinical Chemistry and Laboratory Medicine recommend the routine use of non-fasting lipid profiles, with fasting sampling considered only when non-fasting triglycerides are >5 mmol/L (440 mg/dL) 4.
• Laboratory reports should flag abnormal concentrations based on desirable concentration cut-points, with non-fasting and fasting measurements being complementary but not mutually exclusive 4.
• Nonfasting cholesterol measurement is a reasonable alternative to fasting cholesterol measurement for routine screening, with fasting becoming more important for monitoring triglyceride and low-density lipoprotein cholesterol levels in patients taking lipid-lowering medications 5.