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!
Pharmacology - Nursing Flashcards
Injection and needle terminology
When discussing how to prepare and administer injections, it is important to understand some key terms.
Ampule
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.
Vial
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.
Filter needle
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.
Needle gauge
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.
Needle length
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.
Intradermal injections
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.
Subcutaneous injections
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?
Subcutaneous injections are used to administer larger volumes of medication that may take longer to be absorbed, such as insulin, morphine, diacetylmorphine, and goserelin.
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
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.
Insulin administration
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.
After administering insulin, monitor for signs of hypoglycemia, for example, shaking, weakness, diaphoresis (excessive sweating), or tachycardia.
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 insulin
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.
Intramuscular injections
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.
Z-track method
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.