Butterfly Needles Explained

Butterfly Needles Explained


A butterfly needle, also known as a scalp vein set or a winged infusion set, is a device specialized for venipuncture. It is used to access a superficial vein for phlebotomy or IV injections. Unlike a straight needle, a butterfly needle is less painful and is easier to use, because of the winged tubing that allows for greater flexibility, when dealing with difficult veins or those that are hard to see and feel.

The size of butterfly needles ranges from 18 to 27 gauge bore. The higher the number, the thinner the needle gets. This is why 21G and 23G are the most common, while 25G and 27G are mostly avoided, because it is believed to clot or hemolyze the blood samples, making them invalid for blood tests.


Types of Butterfly Needles


  1. Standard safety device

This type of needle has been the industry standard for many years. Two of its most common sizes are 21G and 23G. A standard safety unit consists of a needle, tubing, and a sheathed needle attached to a hub that will be used in the evacuated tube system. It can also come with a luer lock used with a syringe.


  1. Push button safety device

This is a relatively new type of butterfly, available in varying sizes, including 21G and 23G. A unit consists of the same parts as the standard safety device, including a luer lock for use with a syringe.

Newer models of the winged infusion set comes with a slide and lock safety device, designed to prevent needlestick injury and reuse of needles, both of which increases the risk of infectious disease being transmitted. A phlebotomist only needs to slide the device over the needle after use.


Advantages of using a butterfly needle

  • It allows a phlebotomist to reach more body surface because of its flexible tubing.
  • The same flexible tubing are more tolerable to patient movement, while keeping the pain of intrusion minimal.
  • It is designed for precise placement of the needle on fragile, thin, rolling or poorly accessible veins.
  • It is designed for shallow angle insertion, making it easy to facilitate venipuncture on hand, wrist, and scalp veins.


When is a butterfly needle used?

  • When performing Phlebotomy on geriatrics, infants/children, and in patients with difficult draws. This procedure uses a needle size of 23G.
  • When collecting large quantities of blood needed for testing, such as blood cultures. 21G butterfly needles are used for the procedure.


How to use a butterfly needle

During venipuncture procedure, a phlebotomist holds the wings of the butterfly needle between the thumb and index finger. The needle is then inserted at a shallow angle, often controlled by the winged infusion set’s design. When a “flash” signal appears, which refers to a small amount of blood that gets into the transparent tubing, the phlebotomist will know that they are “in”.


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