Final answer:
For routine adult venipuncture, a 20- to 21-gauge needle is commonly used. It balances adequate flow for blood draws with patient comfort.
Step-by-step explanation:
The needle gauge typically used for routine adult venipuncture is a 20- to 21-gauge needle. A smaller gauge number indicates a larger diameter needle, and vice versa. Larger needles (such as the 16-gauge) are typically used for rapid administration of fluids or for apheresis procedures, where a faster flow is required. Smaller needles (like the 23- or 30-gauge) are often used for children or for administering medications intramuscularly, where a smaller volume and flow rate is suitable. The 20- to 21-gauge size provides a balance between allowing adequate flow for blood draws while minimizing discomfort for the patient.