From the Guidelines
Not fasting before a cholesterol test does not significantly affect the results for total cholesterol and HDL-C levels, but it may affect triglyceride and LDL-C levels. According to the most recent and highest quality study 1, a nonfasting lipid profile provides acceptably accurate measures for risk calculation, and the small variance in LDL-C level is unlikely to affect classification of risk or therapeutic decisions. The study found that nonfasting LDL-C level may be 10% lower and triglyceride levels may be as much as 20% higher compared to fasting measures.
Key Points to Consider
- Nonfasting tests may still be useful for HDL cholesterol and total cholesterol measurements, which are less affected by recent food intake 1.
- For the most accurate assessment of your cardiovascular risk profile, especially for triglycerides and LDL cholesterol, following your healthcare provider's fasting instructions is important 1.
- Some newer guidelines suggest non-fasting tests may be acceptable in certain situations, but you should always follow your doctor's specific instructions regarding whether to fast before your particular cholesterol test 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 fasting lipid profile may be necessary 1.
Clinical Implications
- The American College of Cardiology/American Heart Association task force on clinical practice guidelines recommends that a nonfasting sample is effective to document baseline lipid levels before initiation of statin therapy in individuals with clinical ASCVD 1.
- In adults with a family history of premature ASCVD or genetic hyperlipidemia, a fasting lipid profile is reasonable for initial evaluation to aid in the understanding and identification of familial lipid disorders 1.
From the Research
Effect of Not Fasting on Cholesterol Test Results
- Not fasting before a cholesterol test may have minimal effects on the results, with studies showing small changes in total cholesterol, high-density lipoprotein (HDL) cholesterol, and low-density lipoprotein (LDL) cholesterol levels 2, 3, 4, 5.
- The changes in lipid levels due to fasting status are generally considered clinically insignificant, with maximal mean changes of +0.3 mmol/L (26 mg/dL) for triglycerides, -0.2 mmol/L (8 mg/dL) for total cholesterol, -0.2 mmol/L (8 mg/dL) for LDL cholesterol, and -0.1 mmol/L (4 mg/dL) for HDL cholesterol 3.
- Nonfasting cholesterol measurements have been shown to predict outcomes at least as well as fasting cholesterol measurements, and may even be superior in predicting cardiovascular risk 6, 3, 5.
Clinical Implications
- For routine screening, nonfasting cholesterol measurement is considered a reasonable alternative to fasting cholesterol measurement, and may improve patient compliance and safety 2, 6, 5.
- However, fasting may still be important for monitoring triglyceride and LDL cholesterol levels in patients taking lipid-lowering medications, and for patients with diabetes due to the risk of hypoglycemia 2.
- Several societies' guidelines and statements endorse nonfasting lipid profiles, simplifying blood sampling for patients, laboratories, and clinicians worldwide 3, 5.