From the Guidelines
Not fasting before a lipid panel can cause LDL cholesterol to appear more elevated than it actually is, but the difference is relatively modest and may not significantly impact risk assessment or therapeutic decisions. According to the 2018 AHA/ACC/AACVPR/AAPA/ABC/ACPM/ADA/AGS/APhA/ASPC/NLA/PCNA guideline on the management of blood cholesterol 1, the non-fasting state can increase triglyceride levels, which can interfere with the calculation of LDL cholesterol using the Friedewald equation. However, the guideline suggests that a non-fasting sample is generally adequate to document baseline lipid levels prior to initiation of statin therapy, given the relatively modest differences in LDL-C levels between fasting and non-fasting samples.
Some key points to consider:
- The Friedewald equation becomes less accurate when triglycerides are elevated after eating, which can artificially inflate the calculated LDL value 1.
- The non-fasting state can increase triglyceride levels by 20-30%, but this may not significantly impact risk assessment or therapeutic decisions 1.
- A fasting lipid profile is reasonable for initial evaluation in adults with a family history of premature ASCVD or genetic hyperlipidemia, but a non-fasting sample is generally adequate for most situations 1.
- The unreliability of the Friedewald-calculated LDL-C levels rises at lower levels of LDL-C, particularly <70 mg/dL (<1.8 mmol/L), and calculation adjustments can be used if accurate measurements are needed 1.
In terms of clinical practice, a non-fasting lipid profile is generally acceptable for risk assessment and therapeutic decisions, but a fasting lipid profile may be recommended in certain situations, such as in adults with a family history of premature ASCVD or genetic hyperlipidemia. Ultimately, the decision to use a fasting or non-fasting lipid profile should be based on individual patient needs and clinical judgment, taking into account the potential benefits and limitations of each approach 1.
From the Research
Effect of Fasting on LDL Levels
- Not fasting may not significantly affect LDL levels, with studies showing minimal changes in response to normal food intake 2, 3
- Maximal mean changes in LDL cholesterol levels after habitual meals are reported to be around -0.2 mmol/L (8 mg/dL) 2, 3
- Non-fasting lipid profiles are considered a reasonable alternative to fasting lipid profiles for routine screening 4
Clinical Implications
- The use of non-fasting lipid profiles may improve patient compliance and safety, particularly for individuals with diabetes who are at risk of hypoglycemia due to fasting 2, 4
- Laboratory reports should flag abnormal concentrations based on desirable concentration cutpoints, regardless of fasting status 3
- Fasting sampling may be considered when non-fasting triglycerides are >5 mmol/L (440 mg/dL) 3
LDL Measurement and Cardiovascular Risk
- Non-fasting lipid profiles have been shown to be superior to fasting profiles in predicting cardiovascular risk 2
- LDL cholesterol levels are a major cardiovascular risk factor, and reducing these levels can decrease the risk of atherosclerotic cardiovascular disease (ASCVD) 5
- The measurement of LDL cholesterol levels, whether fasting or non-fasting, is an important aspect of cardiovascular risk assessment 2, 4, 3