Final answer:
A 12-hour fast is usually required before testing for triglycerides to ensure accurate measurements by eliminating the influence of recent meals. Option d.
Step-by-step explanation:
Among the analytes mentioned, triglycerides are typically the one for which a 12-hour fast is required before testing. Fasting is necessary to eliminate the effects of recent food intake on triglyceride levels, which can significantly alter the results.
As noted in endocrinology practices, fasting states are essential for many blood tests to accurately assess organ function and diagnose diseases. Tests such as the A1C are also important, they monitor long-term blood glucose management without the need for fasting. Option d.