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Choosing the Correct Needle Gauge for Injections

When preparing to give an injection, in addition to the five rights of medication administration, it is important to select the correct needle. The solution (type and volume) being injected, the location, and the method of injection will determine both the ideal needle length and gauge. This post will focus on selecting the correct needle gauge.

Why Use Different Gauges?

Needle gauges usually range from 18G to 32G, with larger gauges corresponding to thinner, finer needles. Thinner needles tend to cause less pain, while larger, thicker needles are required for more viscous solutions or higher volumes. Frequent, hypodermic injections, such as insulin injections, are given using microneedles, which are 30–32G. Unfortunately, most other injections will require a larger needle to penetrate thicker tissue.

Intradermal Injections

Intradermal injections, like a tuberculin skin test, are given using a 26–28G needle. This needle penetrates the skin and distributes the solution into the dermis. These injections are typically less than 0.5mL.

Subcutaneous Injections

Subcutaneous injections are administered into the fatty tissue beneath the dermis, and the amount administered is usually less than 1mL, and the recommendation is to use a 26–30G needle.

Intramuscular Injections

Intramuscular injections require a longer and sometimes thicker needle to go through both the dermis and subcutaneous tissue and into the muscle. These injections can be administered with needles ranging from 18–27G. However, it is most common to administer an intramuscular injection to an infant using a 25–27G needle, while a 23–25G needle is more appropriate for a child or adult.

Choosing the Correct Needle Gauge

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