Why is venous blood preferred over capillary blood for many laboratory tests?

Venous blood is preferred over capillary blood for many laboratory tests primarily because it provides a larger volume and a more consistent composition. Venous blood samples can typically yield sufficient quantities necessary for a wide range of tests, which is especially important for those requiring larger volumes or multiple tests to be conducted from a single draw.

Additionally, venous blood generally reflects the body's physiological state more accurately, as it contains a stable concentration of cells and substances, while capillary blood can show variations due to localized factors such as the site of collection and the interstitial fluid present. These characteristics of venous blood contribute to more reliable and reproducible test results, making it the preferred choice in many diagnostic situations.