When performing a routine phlebotomy, the most common gauge needle is

In routine phlebotomy, the most commonly used needle gauge is20 or 21. This size is suitable for venipuncture as it allows for efficient blood flow without causing excessive trauma to the vein. Smaller gauges (like 25 or 26) are typically used for intradermal or subcutaneous injections, while larger gauges (like 18) are used for procedures requiring rapid infusion or blood donation.