Which gauge needle is typically used for adult venipuncture?

The 21-gauge needle is typically used for adult venipuncture because it provides a balance between sufficient flow rate for blood collection and minimizing potential damage to the vein. This gauge is large enough to allow for the swift collection of samples while being small enough to reduce discomfort for the patient.

Using a larger gauge needle, such as an 18-gauge, might be appropriate for blood transfusions or rapid infusions but can cause more trauma to smaller veins used for routine blood draws. Conversely, smaller gauge needles like 23-gauge or 25-gauge are more suitable for pediatric or smaller veins, where minimizing the risk of rupture is crucial, but they may lead to slower flow rates and inadequate sample volumes for certain tests in adults. This makes the 21-gauge needle the optimal choice for standard adult venipuncture procedures.