Butterfly Needles: What Are They & Amp; How Are They Used?


Blood tests are one of the most common and important tests for patients in both hospital and outpatient settings. By testing blood, doctors have a quick way to evaluate multiple organs and systems in the body. Not all needles used to draw blood are the same. One good option is the butterfly needle, which can also be used for IV fluids and medications. Although there are some disadvantages, a butterfly needle is generally a safe, effective option for healthcare workers.

What Is A Butterfly Needle?

Classically, a needle is simply a hollow needle that can be attached to a tube or syringe to either remove or insert fluids into the body. Some needles are double sided, with a smaller needle to penetrate the skin and a larger needle to go through a rubber stop and transfer blood into a test tube.

A butterfly separates these two elements. The needle to penetrate the skin is attached to a flexible tube, and this runs to a larger needle that can transfer blood to a test tube. Another variant has an attachment for without the larger needle. On both types there is a double-winged plastic tab near the needle to penetrate the skin. The whole contraption looks like a butterfly, which gave this device its name.

Are There Benefits To Using The Butterfly Needle?

For blood samples, the needle attached to a butterfly tends to be smaller than the standard needle commonly used. Combined with the flexible tube, this tends to make a butterfly more comfortable than standard needles. Also, they are less likely to cause a vein to collapse, making them advantageous for children, geriatric patients, or others with small veins.

Another advantage of this is that smaller veins can be used to obtain samples, such as those on the back of the hand. There are also advantages that a butterfly provides during its use.

Wh​​​​​ile Inserted in a Pa​​​​t​​​​ient

Retractable Needles

IV Use

Butterfly Needle Info And Tips

Although the smaller needle on a butterfly increases comfort, less blood flows through the smaller opening, making blood sample take longer than with standard needles. Healthcare workers should be patient when using a butterfly. 

One tip when using inserting a butterfly needle into a vein is to look for the "flash." This is when a small portion of blood enters the tube attached to the butterfly and tells the healthcare worker that the needle is inside the vein.

One thing to note is that the smaller needle and reduced movement of a butterfly will help decrease bleeding after a blood sample is drawn. This can be very important for patients with a clotting disorder like hemophilia or Von Willebrand disease.

Still, a smaller needle can have disadvantages. 25 or 27 gauge needles are so small that blood could clot inside the needle or blood cells could be destroyed. Fortunately, most butterfly needles are large, at 21 or 23 gauge. Also, a study showed that blood drawn from a butterfly was less likely to be destroyed compared to that when drawn from an IV catheter.


A butterfly needle is an excellent option for healthcare workers who need to access a patient's vein, both to draw blood samples and also to input fluids through an IV. They provide a more comfortable option during blood samples and can be used on smaller, more delicate veins, including those on the back of the hand.

For IV use, the tube attached to the needle can be attached to an IV bag and used for fluids, medications, and other tasks when used for a short timeframe. Healthcare workers should be patient as blood flows more slowly, and they should also watch for the flash of blood when inserting the needle.

Although these are good benefits by themselves, a butterfly needle can also reduce needle sticks. This is an important benefit to protect healthcare workers from being accidentally infected with serious diseases such as HIV and hepatitis B. For this reason, many institutions have begun using a butterfly for all blood draws and eliminating the traditional needles.

Author: Emma Campbell

I am a director at the Phlebotomy Training Institute