Pharm Basics, part 6: Routes of Administration: Intradermal, Subcutaneous, Intramuscular
by Cathy Parkes August 13, 2021 Updated: August 09, 2023 7 min read
This article covers the preparation of injections, including intradermal, subcutaneous, and intramuscular routes of administration, highlighting best practices and key points. These are topics that may appear on the NCLEX or other nursing exams.
This series follows along with our Pharmacology Basics and Safe Medication Administration Flashcards for Nursing Students which are intended to help RN and PN nursing students build a strong foundation going into Pharmacology and as preparation for the ATI, HESI, and NCLEX.
Note that this article is not intended to offer step-by-step instructions on how to perform these injections; that information can be found in the Level Up RN clinical skills flashcards.
When you see this Cool Chicken, that indicates one of Cathy's silly mnemonics to help you remember. The Cool Chicken hints in these articles are just a taste of what's available across our Level Up RN Flashcards for nursing students!
Injection and needle terminology
When discussing how to prepare and administer injections, it is important to understand some key terms.
An ampule is a small, hermetically sealed flask or container made of glass or polyethylene that contains medication. Ampules usually contain a single dose of medication.
A vial is a small glass or plastic vessel or bottle used to store medication, such as liquids, powders, or capsules. While similar to an ampule, vials tend to be bigger and can contain multiple doses of a medication, which can then be stored and reused.
A filter needle places a glass filtering device at the base of a syringe needle. The filter creates a one-way flow when withdrawing or injecting fluid into or from the syringe. Filter needles are useful when opening a glass ampule, which must be broken at the neck to access the medication inside. Breaking the glass can leave minute shards of glass inside the container, which can result in inflammation of the veins or infection. A filter needle reduces the chances that any glass is introduced into the medication.
A needle’s gauge refers to the size of the hole in the needle. If you are familiar with the world of ear piercings, this is the same meaning of the word gauge! The most common needle gauges are 18, 20, and 22. Choosing the correct gauge size depends on the type of medication to be administered.
The length of a needle varies, depending on the type of injection to be administered and where on the body the injection will be given.
A needle’s gauge and size are defined in a single measurement. For example, “25G 1/2" refers to a 25-gauge, 1/2-inch-long needle.
Best practices for removing medication from ampules and vials
Before administering an injection, the correct dose of medication must be extracted from its container. As noted above, an ampule has a pre-measured (single) dose of medication and a vial usually contains multiple doses.
Removing medication from an ampule
To remove medication from an ampule, take a small gauze pad and wrap it around the neck of the ampule. Then snap the top off at the scored line, breaking the ampule away from your body. This means pulling the top of the ampule toward yourself.
When drawing up the medication, use a filter needle. Remember, this is to keep any minute shards of glass from mixing into the medication.
Do not put air into the ampule as you draw up the medication, and never touch the rim of the ampule, which could contaminate the medication.
Removing medication from a vial
Removing medication from a vial is more common than removing it from an ampule.
To remove medication from a vial, first scrub the top of the vial for 15 seconds with an alcohol swab or other antimicrobial swab.
Insert the needle and inject the amount of air that is equal to the dose of medication into the vial. For example, to draw up 1 milliliter of medication, inject 1 milliliter of air into the vial. Injecting air keeps a vacuum from forming, so the medicine will flow easily into the syringe.
Next, without removing the needle, invert the vial (turn it upside down) and ensure the medicine covers the tip of the needle as you draw up the medication.
An intradermal injection is an injection administered into the dermis, just below the epidermis (skin). It is a shallow or superficial injection of a substance, providing a local versus a systemic effect.
When is an intradermal injection used?
Intradermal injections may be used for diagnostic purposes, e.g., allergy or tuberculosis testing.
When choosing a needle size, use a 26- to 29-gauge needle, between 3/8 and 1/2 inch in length. Only a small amount of medication is administered through this route, ranging from 0.01 - 0.1 milliliters.
How to administer an intradermal injection
To administer an intradermal injection, spread the patient's skin taut with the thumb and index finger of your non-dominant hand.
Apply the needle bevel-up at a 10- to 15-degree angle, then advance the needle until the bevel is just under skin. Do not aspirate once the needle is inserted.
Slowly inject the medication to form a small bubble or wheal under the skin, then remove the needle quickly.
Note that we do not massage the site after removing the needle.
A subcutaneous injection is a type of injection, using a short needle to inject a drug into the tissue layer between the skin and the muscle.
When is a subcutaneous injection used?
For subcutaneous injections, use a 25- to 27-gauge needle, which may vary in length between 3/8 and 5/8 of an inch. The volume of medication will range between 0.5 and 2 milliliters.
How to administer a subcutaneous injection
Perform the injection in a fatty area of the body, for example the abdomen or upper lateral arm.
It is important to rotate injection sites to reduce the risk of developing lipohypertrophy (when lumps of fat or scar tissue form under the skin) and give the skin a chance to heal.
Insert the needle at a 45- to 90-degree angle; for obese patients, always use a 90-degree angle.
When administering an insulin injection, use a special insulin syringe, as these syringes are marked with measurement units to ensure the correct dosage.
Insulin is used to treat diabetes, and comes as short- or long-acting medication.
Short-acting insulins take effect and wear off more quickly than long-acting insulins, which release in a slow, steady manner to help control blood sugar between meals and overnight.
The way to distinguish short- and long-acting insulins is “Clear before Cloudy”: if the medication appears clear, it is shorter-acting insulin; if it appears cloudy, it is longer-acting insulin.
NPH (neutral protamine Hagedorn) is an intermediate insulin, and insulin glargine is a long-acting, man-made version of human insulin. Note that we never mix longer-acting insulin with any other insulin.
When working with insulin, follow these best practices.
Gently rotate the vial prior to administration. Never shake insulin!
As noted above, rotate injection sites to prevent lipohypertrophy.
“Clear before cloudy” — remember, if you are administering a short-acting insulin, it should be clear in color. If it is cloudy or discolored, do not administer it.
In the event of hypoglycemia in a fully conscious patient, administer 15 g glucose (e.g., 4 oz. of orange juice or 8 oz. of milk). For patients who are not fully conscious, administer intramuscular glucagon.
Mixing insulins is a skill you may not need to use very often in your nursing career, as insulins now mostly come premixed, but as Cathy notes in the video, you definitely do need to know it for the NCLEX. For example, a patient may require a mixture of short-acting insulin with an intermediate insulin like NPH. These can be mixed to avoid giving two injections when one will suffice. Long acting insulin is never mixed.
When mixing insulin, follow these steps:
- Inject air into the cloudy insulin. Remove the needle.
- Inject air into the clear, shorter-acting insulin. Don't remove the needle.
- Draw up the short-acting insulin into the needle. Remove the needle.
- Draw up the longer-acting insulin.
Another way to remember the order of mixing insulins is to think of “RN”. Draw up Regular, then NPH.
Long-acting is lonely.
An intramuscular injection (IM) is a technique used to deliver a medication deep into the muscles, allowing medication to be absorbed into the bloodstream.
When is an intramuscular injection used?
Intramuscular injections are used to deliver vaccines and other drugs.
For an IM, use a 20- to 23-gauge needle, which may vary in length between 1/2 to 1 inch in length. The needle is longer than those used in intradermal and subcutaneous injections because it has to penetrate the epidermis, the dermis, the fat tissue, and the subcutaneous tissue to deliver the medication into the muscle.
The volume of medication will vary: for children under 2-years old, the maximum volume should be ≤ 1 mL; for adults, the maximum volume is ≤ 1 mL for the deltoid muscle and ≤ 3 mL for the vastus lateralis (part of the anterior compartment of the thigh) and ventrogluteal (an area on the side of the hip).
How to administer an intramuscular injection
It is important to choose the right muscle for an IM. For infants, use the vastus lateralis muscle. For older children and adults, use the ventrogluteal site or the deltoid site. Note that the dorsogluteal site is rarely used for an IM injection due to the risk of sciatic nerve damage with those injections.
For all of these sites, the injection angle is 90-degrees.
Occasionally a medication must be administered that can stain the tissue, for example iron dextran (an iron supplement). In this situation, we use the Z-track method:
- With your non-dominant hand, gently push the skin and underlying tissue to the side.
- Insert the needle and inject the medication with your dominant hand.
- Remove the needle.
- Release the skin, and let it fall back in place on its own.
Hi, I'm Cathy with Level Up RN. In this video, we will be talking about preparation of injections, and I'll also be covering intradermal, subcutaneous, and intramuscular routes of administration. At the end of the video, I'll provide you guys with a quick quiz to test your understanding of the information I'll be covering. My focus during this video are on the best practices and key points about these routes of administration. So you may get questions about these on the NCLEX or your nursing exams. This video isn't intended to give you step-by-step instructions on how to perform these injections. You can find that information in our nursing skills playlist.
All right. So let's first talk about how to prepare an injection. If you need to remove medication from an ampule, you want to take a small gauze pad and kind of wrap it around the neck of the ampule. And then you want to break the ampule away from the body. So you're going to pull the top of the ampule towards you. Then you want to draw up the medication using a filter needle, and you do not put air into the ampule, as opposed to a vial, which we do want to put air into a vial when we're drawing up medication. So removing medication from a vial is much more common than from an ampule, but you still need to know how to do both, obviously. So with the vial, we're going to want to scrub the top of the vial for 15 seconds with an alcohol swab or other antimicrobial swab. Then we want to inject the amount of air that is equal to the medication dose into the vial. So if we have to draw up 1 milliliter of the medication, we want to inject 1 milliliter of air. And then without removing the needle, we're going to turn that vial upside down, make sure our needle is in the liquid, and then draw up that 1 milliliter of medication.
When we are doing an intradermal injection, we're going to use a 26- to 29- gauge needle that may vary in size between 3/8 and 1/2 inch. We're only going to inject a very small amount of volume through this route, so a max of 0.1 milliliters. In terms of best practices, we're going to hold the skin taut with our nondominant hand, and we're going to inject the needle at a 10- to 15-degree angle, just until the bevel is under the skin. And then we're going to slowly inject the medication to form a small bubble or wheal under the skin. And then we're going to remove the needle quickly and not massage the site. So the most common scenario where we would do an intradermal injection is with a TB skin test.
For subcutaneous injections, we want to use a 25- to 27-gauge needle that may vary in length between 3/8 and 5/8 of an inch. We can definitely inject a lot more volume subcutaneously as compared to an intradermal injection. So volume amounts may range between 0.5 and 2 milliliters. We want to perform our injection in a fatty area of the body, so this can include the abdomen or the upper lateral arm. We want to make sure we rotate injection sites, and we will inject at a 45- to 90-degree angle. If your patient is on the heavier side of things, then a 90-degree angle would be most appropriate. If you are having to do an insulin injection, you want to use a special insulin syringe, as these syringes are marked with units.
And then there are some special teaching and some key points that I want to convey here about insulin administration. So, first of all, if you are administering a short-acting insulin for your patient, that short-acting insulin should be clear in color. If it looks cloudy or discolored, you do not want to administer it. If you are administering an insulin suspension, you want to gently rotate the vial prior to drawing it up. You never want to shake that insulin suspension. And then, in terms of injection, just like with our other subcutaneous injections, we want to rotate sites in order to prevent lipohypertrophy, which is a buildup of scar tissue that would occur if you keep doing an injection in the same site over and over again.
All right. Next, let's talk about mixing insulins. And I have to be honest with you here that the chance of you needing to mix insulins when you become a nurse is pretty low. So I share an office with the diabetic educator from my hospital, and I asked her about mixing insulin. She's like, "Where is this happening?" And I'm like, "It's a big thing in nursing school. You have to know this for the NCLEX and nursing exams." And she was like, "No. They kind of come premixed these days. We don't really have people mix insulin." So, like I said, you have to know it for nursing school. It's important. But following nursing school, you will likely not have to mix insulins.
But in the meantime, here are the important steps for knowing how to mix insulin. I want you to remember clear before cloudy. So remember, clear is going to be our shorter-acting insulin, and our cloudy insulin is going to be our longer-acting insulin, such as NPH. Of note, we are not mixing long-acting insulin. So insulin glargine is a long-acting insulin. We're not mixing long-acting insulins with any other insulin. So our little cool chicken hint here on the card is long-acting is lonely. They both start with L. So when I say longer-acting, I'm referring to NPH insulin. So here are the steps. First of all, you want to inject air into the longer-acting insulin, so the NPH. And then you want to remove the needle, and you want to inject air in the shorter-acting insulin, such as regular insulin. And then, without removing the needle from that regular insulin, you want to invert the vial and remove the regular insulin, put down the vial, and then go over to the longer-acting insulin, the NPH insulin, and remove that insulin. Okay? And those are the steps on how to mix insulin that you have to know for nursing school, but at some point, after you graduate, you can likely purge from your mind.
For intramuscular injections, we want to use a 20- to 23-gauge needle, and the needle length will be much longer than what we've seen with the previous routes of administration. So the needle size will be between 1 and 1 1/2 inches. And it makes sense that it's longer because, if you think about it, we have the epidermis, the dermis, the fat tissue, so the subcutaneous tissue, and then the muscle. So we've got to get through all of those layers to get to the muscle, which is why the needle length is going to be longer. In terms of the injection site, if we are administering an IM injection to an infant, we want to use the vastus lateralis muscle. We don't want to use the deltoid muscle or the ventrogluteal muscle. The vastus lateralis muscle is going to be the right one to use for infants. Now, as children get older and for adults, we can use that ventrogluteal site or the deltoid site. We don't often use the dorsogluteal site due to the risk for sciatic nerve damage with those injections. In terms of the injection angle, we want to use a 90-degree angle. And if we are injecting a medication that can stain the tissue, such as iron dextran, which is an iron supplement, we want to use a Z-track method. So with the Z-track method, we would take our nondominant hand and kind of push the skin and underlying tissue to the side, put the needle in, perform the injection, pull the needle out, and then let the skin go back in place.
All right. It's time for a quiz. I have three questions for you. First question, what type of needle do you use to draw up medicine from an ampule? The answer is a filter needle. Question number two, what angle do you insert the needle for an intradermal injection? If you said 10 to 15 degrees, you are correct. Number three, what is the best site to use when giving an IM injection to an infant? If you said the vastus lateralis muscle, you're right. I hope you did great with that quiz. If not, just go back and watch the video, review our cards again. You got this. Thanks so much for watching.
For subcutaneous injections, we want to use a 20-- sorry. For intradermal-- nope, I'm on intramuscular.
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