IV Needle Sizes

Giving a patient an IV is much more complicated than it seems. While sticking a needle in someone's body is quite straightforward, picking the right IV gauge size, width, and diameter requires you to fully understand the importance of each.

Individual medical facilities have their own processes and protocols, but certain aspects are standardized across the industry.

In a few words, an IV's measurements will influence when you should use it, who you can give it to, and what type of fluids the needle is capable of transmitting.

How are IVs measured?

Medical professionals measure IVs by their gauges. The relationship between the IV needle size and gauges is inverted.

To put it another way, IVs with a small gauge typically have a bigger needle length and diameter. Conversely, as the IV's gauge number increases, the needle's length and diameter decrease.

For example, 14-gauge needles tend to be 45-millimeters (mm) long and 2.1 mm wide, while 26-gauge needles are generally 19-mm long and 0.6-mm wide.

Why is gauge size important?

Gauge sizes are important for several reasons.

Firstly, the amount of IV fluid that the patient needs determines the suitable gauge size. When administering a small amount of medication, you want to use a thin needle with a large gauge.

In the same vein, using a bigger needle with a smaller gauge allows you to deliver higher quantities of the medication in a single dose. This means that you don’t have to stick multiple needles in a patient’s body.

Secondly, the appropriate gauge size depends on the thickness and viscosity of the IV fluid. Thicker liquids require IVs with wide diameters and small gauge sizes. Meanwhile, thin fluids can quickly be transmitted through a small-gauged needle that has a narrower diameter.

Lastly, but certainly not least, is that wide needles (which have a relatively small gauge) can quickly transfer medications to the patient's body. This is critical during emergencies, such as heart attacks and urgently-needed blood transfusions.

General Rules

IV needles have standardized gauge sizes that range from 14 to 26 gauges. The medical industry established rules and recommendations for using each of them, and they are as follows:

14 Gauges

The IV catheter’s diameter of these needles is 2.1 mm, which is perhaps the widest available type. A 14-gauge IV is used during surgeries and rapid blood transfusions.

16 Gauges

Similarly, these wide gauges are commonly found in urgent care units (ICUs) and surgery areas.

Because of their 1.8-mm width, 16-gauge IVs can quickly deliver fluids. They are incredibly valuable when a patient's body loses a lot of fluids or blood that need to be immediately replaced.

18 Gauges

This gauge size comes with a 1.3-mm-wide needle, and its uses are almost identical to a 16-gauge IV.

An 18-gauge needle can rapidly administer blood and push fluids. Additionally, these IVs are utilized for CT PE protocols and comparable imaging tests.

20 Gauges

Most of the time, medical professionals rely on 20-gauge IVs for general infusions. They also resort to them to transfer blood if 18-gauge needles aren't available or when treating patients that have relatively small veins.

22 Gauges

This gauge size is used for typical infusions, as well.

Although their 0.9-mm diameter is sometimes too narrow for blood to go through, some hospitals and clinics may perform routine (and not urgent) blood transfusion with a 22-gauge IV.

Furthermore, these needles are handy when a patient doesn't require a lot of fluids and for treating older adults and children.

24 Gauges

24-gauge needles are only deployed as a last-resort option, especially amongst adults. However, your employer may allow you to use them when a child or infant needs a blood transfusion and for routine ones amongst adults.

26 Gauges

These are the largest-gauged and narrowest needles. They have a diameter of only 0.6 mm.

You can only rely on these IVs in specific circumstances, and most of them pertain to children and infants.

A Summary

In the medical industry, every gauge size has a specific color. It is crucial for you to know them because they enable you to rapidly make decisions during urgent situations and emergencies.

Equally as important are the standard characteristics and measurements of each IV, which are as follows:

  • Length: This is measured in millimeters. Most needles are between 19 and 45-mm long. The longer the needle is, the smaller its gauge is.
  • External Diameter: As mentioned earlier, the width of IV needles is also measured in millimeters and has a negative correlation with the gauge size.
  • Water Flow Rate: In short, this refers to how fast the liquid can go through the IV, measured by milliliters per minute (mL/min). The wider and longer the needle is, the faster its water flow rate will be.

To illustrate, here is a breakdown of these measurements based on the IV's gauge and color:

  • Orange - 14G: 2.1 mm wide; 45 mm long; 240 mL/min water flow rate
  • Gray - 16G: 1.8 mm wide; 45 mm long; ~180 mL/min water flow rate
  • Green - 18G: 1.3 mm wide; 32 mm long; ~90 mL/min water flow rate
  • Pink - 20G: 1.1 mm wide; 32 mm long; ~60 mL/min water flow rate
  • Blue - 22G: 0.9 mm wide; 25 mm long; ~36 mL/min water flow rate
  • Yellow - 24G: 0.7 mm wide; 19 mm long; ~20 mL/min water flow rate
  • Purple - 26G: 0.6 mm wide; 19 mm long; ~13 mL/min water flow rate

All of the above measurements are standardized across the medical industry. This includes the colors, the inverted relationship between gauge sizes and width, and the water flow rate.

Similarly, each of these figures should guide you while you administer IVs, particularly the appropriate gauge sizes for specific procedures, the patient's age, and the viscosity of the fluid.

Once you fully understand these aspects, giving a patient an IV will become just as easy as it looks.