Blood Collection Needle

• Three of the most frequent needle sizes are 21, 22, and 23 gauge.

• The 21g needle, which is commonly color-coded with a green code covering, allows blood to flow at a steady rate, reducing collection time.

• The 22g needle may help the phlebotomist with slightly narrower veins on older children or adult patients. This needle, which has a black color code covering, can be assembled with the more typical multi-sample needle ETS system.

• The 23g needles are used when a person’s vein is much narrower than average. It is light blue color coded.

Unlike standard measurement systems, gauge numbers and needle size have an inverse relationship. The needle width narrows as the gauge number increases. The most widely used needles in the medical industry range from number 7, the largest, to number 33, the smallest. The most widely used needles for venipuncture are 21-gauge needles, while 16-gauge needles are commonly used for blood donation because they are thick enough to allow red blood cells to pass through the needle without being broken.