Syringe needle size question

dgoldrich

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I am currently using a 31g 5/16 needle and it works fine for me. It will occasionally bend, but usually it is great. My friend just started injections and apparently her skin is much thicker and the needle keeps bending and breaking on her....does anyone have a recommendation for what size I should buy for her?
 
I currently use 31g, but my first month I used 29g and it was still very comfortable. You might want to try having her move to 29g first because it's supposed to be a nice "middle ground" syringe for comfort, speed, and sturdiness. If that still doesn't work, then 27g and 28g are used when you need a sturdier syringe or better flow because medication is thicker, but may not be as comfortable to use. Just my two cents from when I trying to determine what to purchase myself since I had to ask for an Rx to buy syringes where I live.
 
Ironically I've been planning a "daily dose of wisdom" post on this very subject, but in the meantime here's my take starting with the outside diameter (OD) of the three most common insulin syringe size needle gauges in mm:

31G .2604mm
30G .3112mm
29G .3366mm

The difference between a 31G and 29G needle is .0762mm.

For reference, a human hair averages something like .16mm, so even completely skipping the 30G size we're literally talking about a thickness difference of around half that of a human hair. I'd be willing to wager that 99.99% of people are incapable of perceiving that difference in size when it comes to how a needle "feels" and it's entirely a function of psychology and not anything determined by the various corpuscles in our skin.

Honestly, everyone starting out should begin with a 29G syringe (I still recommend 8mm over 13mm, but that's another discussion for another day), and give themselves at least a half dozen injections before considering going with a higher gauge and even then only if there are compelling reasons like excessive bleeding or other contributing factors like skin conditions such as psoriasis, scleroderma, or related complications from diabetes.

So yeah, tell your friend 29G is the way to go.
 
Similarly:

From a paramedic textbook, recommending no more than 8mm in length for 90-degree injection:1000004126.jpg

From a clinical skills text, recommending the 29G size for insulin syringes:

NEEDLE-SIZE.png

And why 4 mm is long enough for pen needles:


The safety and efficacy of the 4-mm pen needle have been assessed and proven in several clinical trials in adults and children, as well as in obese and nonobese adults with diabetes [5, 19]. Furthermore, the 4-mm pen needle has been recommended for use in most adult patients of all sizes where the lifting of a skin fold is not required (Fig. 1) [20].

[Not to scale]
1752464707479.png
 
Last edited:
Similarly:

From a paramedic textbook, recommending no more than 8mm in length for 90-degree injection:View attachment 7790

From a clinical skills text, recommending the 29G size for insulin syringes:

View attachment 7791

And why 4 mm is long enough for pen needles:




[Not to scale]
View attachment 7793
21G for IM sounds like Hell on wheels. Almost a decade in the 25's still leave my glutes sore for a day or two.
 
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