Which tests commonly require fasting?

• A. Thyroid function tests.
• B. Lipid panel and sometimes glucose.
• C. Complete blood count.
• D. Urinalysis.

Answer: (B)

Fasting matters most when meals can change the substances being measured. The lipid panel is the classic test that requires fasting because triglycerides rise after eating, and that can also distort LDL calculations, making the lipid levels appear artificially high or low. Some glucose tests do require fasting to get an accurate fasting glucose value or to perform a glucose tolerance test, but not all glucose assessments—nonfasting glucose tests exist as well. In contrast, thyroid function tests, a complete blood count, and a urinalysis are typically unaffected by a recent meal and can be drawn without fasting. So, the statement describing a lipid panel and, in some cases, glucose, best captures which tests commonly require fasting.