Pros & Cons of Butterfly Needle Gauge Sizes


A butterfly needle is used to draw blood from superficial veins or administer medications or intravenous (IV) fluids. Medical professionals might also refer to a butterfly needle as a winged infusion set due to the plastic wings on the sides of the needle. While butterfly needle components vary, they generally feature a flexible, winged covering and tubing, which allows for precise placement and angle insertion. 

Butterfly Needle vs. Straight Needle

A medical professional may opt for a butterfly needle instead of a straight needle because it allows for greater flexibility during angled insertion, accuracy and is typically less painful for the patient. This is because a butterfly needle's bilateral wings and short length allow a phlebotomist to grip close to the needle and precisely place it in the vein.

Butterfly needles also allow venipuncture of thin or fragile veins, such as those found in the hand or scalp. Professionals may use a butterfly needle to perform venipuncture on infants, older adults or patients who are afraid of needles. Although butterfly needles can be secured and left in the vein for about a week, they are often used for short-term infusions or blood collection.

In comparison, a straight needle attaches to a syringe or tube holder and is considered the ideal choice for healthcare workers when multiple blood samples or multiple IV fluids are required.

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What Are the Different Butterfly Needle Gauge Sizes?

Butterfly needles are available in a range of sizes, and they are measured by length and gauge. The gauge refers to the diameter of the bore in the needle. Typically, butterfly needle gauge sizes range from 18 to 27, with higher numbers representing thinner needles with smaller bores. The length of a standard butterfly needle is 3/4 inch.

Pros of Lower Gauge Butterflies

Butterfly needles with larger bores, or those with lower gauges, may be used for certain situations or lab tests. Because most butterfly needles are 21- to 23-gauge, technicians might say an 18- or 20-gauge needle is large. 

Here are a few reasons a medical professional or patient might prefer a butterfly needle with a lower gauge:

  • Less prone to clogging: Some professionals may prefer larger needles because they are less likely to get clogged than thinner needles. Larger needles may be the preferred choice for injecting viscous fluids.
  • May produce more accurate specimens: A larger needle with a lower gauge might be more appropriate for test samples. As the World Health Organization states, a too-small needle may damage blood cells in a process called hemolysis during sampling. Thus, it's critical to ensure proper gauge size for tests that require whole blood cells.
  • Recommended for blood draws: A lower gauge, such as an 18-gauge butterfly needle, is more likely to be used for blood draws when completing blood tests. A larger needle collects blood faster than a smaller one and may be the best choice in emergencies or if a patient is squeamish.

Cons of Lower Butterfly Needle Gauges

Although larger, lower-gauge butterfly needles may be the better option for sample accuracy and collection speed, there are a few disadvantages to keep in mind:

  • More painful for patients: Patients are more likely to experience pain when receiving a larger needle. A painful experience may prevent patients from undergoing procedures in the future.
  • May leave a larger wound: Healthcare professionals using a needle with a lower gauge might leave a larger puncture wound. This may increase the risk of infection for the patient.
  • Not suitable for smaller veins: Lower-gauge needles may not be the right size for smaller veins, such as those in the feet or hands. If a needle is too large for the vein, it could tear the vein.


Pros of Higher Butterfly Needle Gauges

Some patients require smaller-than-average needles or those that are between 25- and 27-gauge. Smaller, higher-gauge needles have advantages for patients with tiny or fragile veins, but they should only be used when necessary.

Pros of higher gauge butterfly needles include the following:

  • Produces a smaller puncture wound: A smaller needle size with a higher gauge makes a tinier puncture wound. This means less bleeding, particularly for patients with disorders such as hemophilia, and a lower risk of infection.
  • Offers a solution for small veins: A higher gauge, such as a size 27 or 28, may be required to access small or narrow veins to minimize pain and risk of vein damage.
  • Can be used with pediatric patients: Children and infants require smaller needles, and it's recommended to use a higher gauge, such as a size 23 or smaller, for venipuncture procedures.
  • Less painful: Studies have shown that higher-gauge needles are less painful than larger needles. Some patients might even request the use of a small butterfly needle.
  • Appropriate for insulin injections: Since insulin doesn't need to go deep into the body, patients might prefer short, thin needles to administer regular insulin injections. And because smaller needles are less painful, patients may be more apt to stick to treatment for diabetes.
  • Less intimidating: High-gauge butterfly needles may appear less threatening to patients who feel uneasy with needles. When patients anticipate less pain, they are more likely to follow through with their medical care.

Cons of Higher Butterfly Needle Gauges

Smaller, higher-gauge butterfly needles cause less pain, but they may not always be appropriate. Here are some disadvantages to keep in mind:

  • May cause hemolysis: Needles with a gauge size 25 or higher are not always recommended because as needle size gets smaller, the risk of hemolysis increases. Hemolysis would render blood samples invalid for certain lab tests. For this reason, a gauge size 25 or greater is only recommended for use with infants or patients with hard-to-access veins.
  • Takes more time: A smaller needle draws blood at a slower rate than a larger one. If blood is urgently needed or a patient cannot sit for long, it may be better to use a lower gauge.

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What Are Butterfly Needles Used For?

Phlebotomists, nurses and other medical professionals frequently use butterfly needles for blood samples for common laboratory tests, such as:

  • A complete blood count
  • Basic metabolic panel
  • Blood enzyme test
  • Lipoprotein panel
  • Sexually transmitted disease test

Since butterfly needles attach to flexible tubing that can connect to a collection container, phlebotomists often use them to collect blood from donors.

Health care staff may also use butterfly needles to administer pain medication or insulin. Sometimes medical professionals use butterfly needles short-term to deliver IV infusions, such as chemotherapy medications, gradually.

How Are Butterfly Needles Used?

To use a butterfly needle, the technician will need to grasp its wings between their thumb and index finger. They'll hold the needle with the bevel, or hole, facing up and the point positioned down. This position makes it easier to pierce the skin.

The technician will then insert the needle into the skin at a 45-degree angle and lower it to enter the vein. It's recommended the phlebotomist pierces the vein with a quick stick to help keep the vein from rolling or bouncing away. The butterfly needle should help prevent rolling veins because the technician can grip closer to the needle to get a more accurate angle.

After insertion, the technician can use the butterfly needle's wings to stabilize it.

Do Butterfly Needles Cause Hemolysis?

Butterfly needles themselves do not cause hemolysis. In some cases, they may reduce the risk of blood cell damage. For example, butterfly needle phlebotomy reduces the rate of hemolysis by more than half in comparison to IV catheter phlebotomy. 

However, smaller, higher-gauge needles increase the risk of damaging blood cells during venipuncture. Research finds that 25-gauge needles impacted blood test results, while larger 23-gauge needles didn't significantly affect samples. To address hemolysis, some manufacturers have created needles with an external higher-gauge diameter but an internal lower-gauge diameter.


Contact Mercedes Scientific for More Information

Choosing the correct needle size is critical for your lab's employees and patients. At Mercedes Scientific, we want to help you make the right choice. We're a customer-focused laboratory and medical supply distributor ready to answer your questions about our butterfly infusion setsContact us to learn more or browse our laboratory needle selection today.