Flow chart for needle length/gauge selection?

**NICU Guy, BSN, RN** · Sep 2, 2013

Subcutaneous Injections go into the fatty tissue below the skin and require a smaller, shorter needle. A needle that is ½ inch to 5/8 of an inch long with a gauge of 25 to 30 is usually sufficient to administer the medication.

Intramuscular Injections go into the muscle below the subcutaneous layer, so the needle must be thicker and longer to ensure that the medicine is being injected into the proper tissue. Twenty (20) or 22 G needles that are an inch or an inch and a half long are usually appropriate for this type of injection. A person who is thin, with very little fatty tissue can use the inch long needle; a heavier person may need to use the inch and a half long needle.

You don't choose needle gauge based of viscosity (you are not putting anything thick into tissue or muscle) and length only matters with thin and obese patients when you are giving an IM injection because you need extra length to get into muscle on heavy people.

olioxenfree · Sep 2, 2013

Our text says that viscosity is a variable.

"Syringes and needles come in many sizes and are selected according to the route the medication is to be given, the patient’s body size, the viscosity (or thickness) of the medication, and the amount of medication to be given."

"GAUGE OF VISCOSITY OF NEEDLE MEDICATION ROUTE EXAMPLES

19–20 Thicker or oil-based medications IM Hormones, steroids, penicillin, and certain

vitamin preparations

21–23 Aqueous- or water-based medications IM Immunizations and other water-based

medications

23–25 Aqueous-based medications Sub-Q Immunizations, allergy medications, etc.

26–27 Aqueous-based medications ID Allergy testing extracts and PPD extract

30 Aqueous-based medications Sub-Q Used when repeated injections are given,

(usually such as insulin ultra-fine point)"

Combine all that with the weight/thickness of patient, route, amount of injection, choosing the site of the injection... and you have an overwhelming list variables to consider and sort out for a newbie LOL

I'm sure once in the hospital/clinical setting it will be more obvious common sense and policy based; however, learning all the rationale and passing a paper test on which/why to choose is a little more little tricky.

I know there has to be an organized chart out there somewhere on the web!!!

Christy1019, ASN, RN · Sep 2, 2013

I agree, Ativan or Bicillin IM are super thick and both are given IM.

**NICU Guy, BSN, RN** · Sep 2, 2013

I think you are trying to make it more difficult than it needs to be.

19–20 Thicker or oil-based medications IM Hormones, steroids, penicillin, and certain
vitamin preparations
21–23 Aqueous- or water-based medications IM Immunizations and other water-based
medications

Like I said in my previous post: 19-22g for IM injections. You could use a 19 or 20g for all IM injections. Using a 21-23 for immunizations would hurt slightly less, but you can use a 19-20g if you wanted.

23–25 Aqueous-based medications Sub-Q Immunizations, allergy medications, etc.
26–27 Aqueous-based medications ID Allergy testing extracts and PPD extract
30 Aqueous-based medications Sub-Q Used when repeated injections are given,
(usually such as insulin ultra-fine point)

23-25 for SQ injections. 26-27g are used primarily for sub-dermal (allergy and PPD) and 30g are used almost exclusively for insulin. 30g are commonly called " insulin syringe".

zzbxdo · Sep 2, 2013

If you can't draw something up then you can't use it that's the extent of it. You can't draw ativan through a tb syringe. K so you just using something else that works but it's not like it'll ever an issue.

Esme12, ASN, BSN, RN · Sep 2, 2013

This chart may help it done for immunizations however there is a nice chart

http://www.vdh.state.va.us/epidemiology/immunization/vfc/documents/forms/VVFCToolkit/Fulltoolkit.pdf