Butterfly needles have advantages over straight needles when collecting blood or delivering IV fluid or medications.
For instance, they allow for more precise placement, particularly in hard-to-access veins.
There are cases in which other needles need to be used, though.
Illustration by Gary Ferster for Verywell Health
Types
While all butterfly needles are similarly designed, there are variations.
Butterfly needles are measured in gauges and typically range in size from 18 gauge to 27 gauge.
The higher the gauge, the smaller the needle.
By way of illustration, a 27-gauge needle is the size commonly used forinsulin injections.
Smaller gauge needles are used if an injectable fluid is thick or if blood is being collected for transfusion.
Most butterfly needles are no more than 3/4 of an inch (19 millimeters).
This is helpful, as there is less chance of injury if either is yanked or dropped.
Tubing can range in size from 8 inches to 15 inches (20 to 35 centimeters).
Some butterfly needle connectors have built-in ports that can be inserted into vacuum tubes.
Other connectors have ports into which syringes or lines can be inserted.
The short, thin needle is inserted toward a vein at a shallow angle.
The puncture wound is then bandaged.
Its use also allows access to small or narrow veins, such as those in infants or older people.
Disadvantages
Butterfly needles are not for everyone.
Because of their small needle size, blood collection tends to be slower.
In cases like these, the selection of the needle size is key.
Summary
Butterfly needles can be a useful way to draw blood or to give IV fluids.
Canadian Agency for Drugs and Technologies in Health; 2020.
2019;9(11):e030576.
2013;20(11):1151-1155. doi:10.1111/acem.12245
