How to Read a Syringe Needle

It is important to use the appropriate needle for the type of injection you are giving.

There are two main components that help you to determine the size of a syringe needle: length and gauge, or thickness. The type of needle you use is dependent on the type of injection you are giving. By simply knowing your purpose and the type of syringe you are using, you can determine the needle you will need to use as well.

Instructions

Intramuscular Injection

1. Select length of needle. Intramuscular injections typically require a needle that is between one and one-and-a-half inches as they are administered deep into the muscle.

2. Select gauge. Intramuscular injections typically require a slightly thicker needle in order to penetrate the muscle. A 20- to 22-gauge needle will work for most of these injections. With needles, the lower the gauge number is, the wider the needle opening is.

3. Determine the dead volume. The dead volume of the needle is the amount of liquid that the needle itself holds, and you will be able to locate this amount on the needle packaging. This does not affect the measurement of liquid you will need in the syringe itself, but you will need a needle that holds a smaller dead weight than the amount of liquid you require.

Subcutaneous Injection

1. Select length of needle. A subcutaneous injection is one that penetrates the first layer of fat that lies just below the skin. A needle length for these injections is typically between 1/2 inch and 5/8 inch.

2. Select the gauge. As the needle goes through less skin, the gauge number must be higher. A gauge of 25 to 30 will work for these injections.

3. Determine the dead volume of the needle.

Tips & Warnings

• For the comfort of the person receiving the injection, use the narrowest needle possible. This will mean that your gauge number will be high. A 25 gauge is narrower than a 22 gauge.

References

• Syringe and Needle
• Gauge Index

Resources

• Read this Article in Spanish