What Are Butterfly Needles?

These can be helpful for blood draws and to deliver IV therapies

A butterfly needle, also known as a scalp vein set or winged infusion set, is a device used to draw blood from a vein or deliver intravenous (IV) therapy to a vein. A butterfly needle consists of a very thin needle, two flexible “wings,” a flexible transparent tubing, and a connector.

The connector can be attached to a tube to collect blood or to tubing from an IV bag to deliver fluids or medications. Medications can also be delivered directly to the connector via a syringe.

Butterfly needles have advantages over straight needles. For instance, they allow for more precise placement, particularly in hard-to-access veins. There are cases in which other needles may need to be used though.

This article will review the butterfly needle, instances in which they are used, as well as some advantages and disadvantages to the needle.

Mistaken Identity

At first glance, a butterfly needle resembles a Huber needle, which is also winged. Huber needles, however, are bent at a 90-degree angle so that they can be securely placed in an implanted chemotherapy port.

What Butterfly Needles Are Used For

Phlebotomists (people who draw blood) regularly use butterfly needles to obtain blood samples for blood-based tests.

Butterfly needles can also be used to deliver intravenous fluids if you are dehydrated and either cannot drink fluids or cannot drink enough to compensate for fluid loss.

Additionally, they are useful for delivering medications (such as pain medications) straight into a vein or infusing IV therapies (such as chemotherapy or antibiotics) intravenously.

Though butterfly needles can be left in a vein for five to seven days if properly secured, they are more commonly used for short-term infusions.

Regular or ongoing infusions are typically given through a larger vein via a central line or peripherally inserted central catheter (PICC) line.

butterfly needles
Verywell / Gary Ferster 


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 for insulin 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 three-quarters of an inch (19 millimeters).

The IV equipment or collection container is attached to tubing that’s connected to the needle, rather than being directly connected to the needle. This is helpful, as there is less chance of injury if either is yanked or dropped.

Tubing can range in size from eight inches to 15 inches (20 to 35 centimeters). Shorter tubes are used for blood draws; longer ones are intended for IV applications and may have roller valves to regulate the flow. The tubes may also be colored so that healthcare providers can differentiate the lines if more than one are used.

Some butterfly needle connectors have built-in “male” ports that can be inserted into vacuum tubes. Other connectors have “female” ports into which syringes or lines can be inserted.

How Butterfly Needles Are Used

During venipuncture (the insertion of a needle into a vein), a phlebotomist or nurse will hold the butterfly needle by its wings between the thumb and index finger. Because the hypodermic needle is short and the grasp is close to the needle, the butterfly needle can be placed more accurately than a straight needle, which can often roll or wiggle in the fingers.

The short, thin needle is inserted toward a vein at a shallow angle. Once inserted, the venous pressure will force a small amount of blood into the transparent tubing, providing confirmation that the needle is correctly placed.

The wings can also serve to stabilize the needle once it is in place, preventing it from rolling or shifting.

Once used (blood is drawn or medication is delivered), the entire unit is thrown away in a sharps disposal container. The puncture wound is then bandaged.


Because of their small size (far smaller than an intravenous catheter) and shallow-angle design, butterfly needles can access superficial veins near the surface of the skin. This not only makes them less painful to use, but allows them to access veins that are small or narrow, such as those in infants or the elderly.

Butterfly needles are ideal for people with small or spastic (rolling) veins, and can even be inserted into the tiny veins of the hand, foot, heel, or scalp.

They are also ideal for people who are hesitant about needles because they are less threatening, and they are less likely to cause profuse bleeding, nerve injury, or a vein collapse once the needle is removed.

Newer models have a slide-and-lock sheath that automatically slides over the needle as it is extracted from a vein. This prevents needlestick injuries and the reuse of a used needle.

If you have been told that you have small veins and have had challenging blood draws in the past, you might consider requesting the use of a butterfly needle.


With that being said, butterfly needles are not for everyone.

Because of their small needle size, blood collection tends to be slower. This can be problematic at a blood bank if a person is squeamish or in urgent situations where blood is needed quickly. In cases like these, the selection of the needle size is key.

Even for a routine blood draw, the wrong needle size can result in blockage and the need for a second draw if a large quantity of blood is needed.

Because a needle is left in the arm rather than a catheter or PICC line for the purpose of an infusion, a butterfly needle can damage a vein if the unit is suddenly yanked. Even if the right size needle is used, the needle can become blocked during treatment if not correctly placed.

As a rule of thumb, butterfly needles should only be used for IV infusions of five hours or less.


Butterfly needles can be a useful way to draw blood or to give IV fluids. However, there may be some times that using a different type of needle may be necessary.

Frequently Asked Questions

  • Can a butterfly needle be used for an IV?

    Yes, a butterfly needle can be used for an IV, to give fluids or other medications.

  • Do butterfly needles hurt less?

    Butterfly needles can hurt less than other types of needles. This is because they can be used for veins closer to the surface of the skin and may be able to use a smaller needle.

  • What kind of veins are butterfly needles used for?

    Butterfly needles can be used in the smaller veins of the extremities.

  • Can butterfly needles be reused?

    Butterfly needles cannot be reused, due to safety and to prevent risk of infection.

2 Sources
Verywell Health uses only high-quality sources, including peer-reviewed studies, to support the facts within our articles. Read our editorial process to learn more about how we fact-check and keep our content accurate, reliable, and trustworthy.
  1. Malamed SF, ed. Chapter 24: venipuncture technique. In: Sedation. 6th ed. Mosby; 2018:308-318.

  2. Ohnishi H, Watanabe M, Watanabe T. Butterfly needles reduce the incidence of nerve injury during phlebotomy. Arch Pathol Lab Med. 2012;136(4):352. doi:10.5858/arpa.2011-0431-LE

Additional Reading

By Julie Scott, MSN, ANP-BC, AOCNP
Julie is an Adult Nurse Practitioner with oncology certification and a healthcare freelance writer with an interest in educating patients and the healthcare community.

Originally written by Pam Stephan
Pam Stephan is a breast cancer survivor.
Learn about our editorial process