In which situation should a venipuncture be performed?

A venipuncture should be performed primarily when a larger volume of blood is needed for tests or when obtaining a sample via fingerstick is not feasible. This is because venipuncture allows for the collection of the required quantity of blood that is often necessary for comprehensive testing, including multiple or specialized tests that can't be conducted with smaller samples.

In cases where the tests require a significant amount of blood, venipuncture is the preferred method as it can draw enough to accommodate additional testing without needing multiple sticks, reducing patient discomfort and increasing the efficiency of specimen collection. Similarly, if a fingerstick is not an option—perhaps due to anatomical issues, the patient’s age, difficulty accessing a suitable capillary site, or if the patient's condition makes a smaller sample impractical—venipuncture becomes the necessary choice.

This rationale demonstrates why selecting both reasons—needing a larger volume and the unsuitability of fingerstick—as the correct answer effectively captures the primary indications for performing a venipuncture.