Needle gauges

What does the gauge of a needle measure, what do the different sizes mean?

[sickNtired222]

The smaller the number, the bigger the needle. For example, a 24 gauge needle is much smaller than a 18 gauge needle. With children the needle will usually be smaller, because their veins are smaller.

[medikat]

The larger the Number, ie 25 gauge vs. 21 gauge the SMALLER the lumen or "barrel width" of the needle tube.  Think of it as a pipe and the distance that measures across the diameter of the opening,,,the larger that width, the greater amount of a substance can pass through. In needle gauges #'s, however....think of opposites:   # 19 gauge is "wider" than a # 25 gauge, which is much smaller, used for subcutaneous injections such as insulin.  A # 23 gauge needle is the standard for an IM injection, but it's lumen is narrower than say a #21 or a #19.  A #23 is usually used to draw blood, unless the patient is a difficult stick, in that case, the "butterfly" a # 25, will be used, usually on the hand. A liquid medication such as B-12 or testosterone is a much thicker medication, so sometimes a smaller "#" on the gauge is indicated, especially condsidering the area where you are shooting....A deep IM injection on the glut area (buttock) on a person that has a bigger layer of body fat may 1) require a longer needle to reach the muscle and 2) a smaller gauge needle which is a "wider" needle" ie gauge # 21 ) to get the med into the system.

[caregiver222]

"Needles" are not always used invasively.

Many large bore needles are used to infuse a solution into an IV set through an elastomeric seal in the line.

A smaller gauge needle will mean a longer time for an intravenous solution to enter the vessel, so if a rapid infusion is required, a larger bore is desired.

Bear in mind that when an intravelous line is started, the "needle" is really what is called a trochar, and is withdrawn after the vein is entered, leaving only a plastic tube within the vein.