What gauge needles are commonly used or blood draws?

Commonly used needle gauges for blood draws are 21-gauge and 22-gauge needles. The 21-gauge needle is often preferred for adults due to its balance between flow rate and comfort, while the 22-gauge is frequently used for pediatric patients or those with smaller veins. In some cases, a 23-gauge needle may be used for very small veins. The choice of gauge depends on the patient's age, vein size, and the volume of blood needed for testing.