The Butterfly Effect

Many patients have been ill advised that they need to be drawn with a butterfly needle. An experienced phlebotomist will smile, assess your veins, and let you know they can draw you with a straight needle. If you have been told that you have small veins and have had challenging blood draws in the past, you might believe you need a butterfly needle. However, it all boils down to the right needle size for your particular draw. The most common needle sizes used for venipuncture are 23, 22, and 21. There is a huge myth about butterflies, truth is they are not the best to use, in actuality they are the last resort. 

Why is that?

  • Butterflies come in the same gauge as straight needles, there is no difference in needle size. The main difference is the wings which provide flexible.
  • There is an increased risk of needle-stick injury when a butterfly needle is used. 
  • Due to the tubing associated with the butterfly needle, it is more likely to clot than the use of a straight needle.
  • Slower flow
  • Butterflies are prone to blockage and the need for a second draw.


As a rule of thumb, butterfly needles are to be used in special circumstances for blood collection.

  1. Very small and fragile veins, e.g. hands, feet, neonates, chronic blood draws
  2. Patient’s with tremors or uncontrolled movements 
  3. Blood Cultures 
  4. Patients who cannot physically or easily change the position of their arms
  5. When 10 or more tubes are to be collected at one time 
  6. IV infusions of five hours or less.


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