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HLT-LPN37-02 · Lesson 7 · 20 clock hours · lab

Subcutaneous, Intradermal, and Intramuscular Injections

Objective. The student will prepare and administer subcutaneous, intradermal, and intramuscular injections using correct site selection, angle, needle length, and aseptic technique on simulation trainers.

⚠ Pending professional review

This lesson, its worked examples and its practice questions has not yet been verified by a licensed clinician in the field or by a certification or approval body. It is a study draft and may contain errors. Do not use it to make decisions about any patient or medication. Always follow your instructor, your supervising professional, and current official references and regulations.

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Introduction to Parenteral Injections

Parenteral medications bypass the gastrointestinal tract and are delivered directly into body tissue or the bloodstream. As an LPN, you will routinely administer three types of injections: subcutaneous (SC), intradermal (ID), and intramuscular (IM). Each route has specific indications, sites, needle specifications, and technique requirements. Mastering these skills protects patients from injury, infection, and medication errors.

Aseptic Technique and Hand Hygiene

Every injection begins and ends with infection control. Perform hand hygiene with soap and water or an alcohol-based hand rub before and after every procedure. Don gloves before handling needles or touching the patient's skin. Use a new sterile needle and syringe for every injection. Cleanse the injection site with an alcohol swab using a circular motion outward from the center, then allow the skin to dry completely before inserting the needle — wet alcohol causes a stinging sensation and can introduce alcohol into tissue.

All needles and syringes go directly into a puncture-resistant sharps container immediately after use. Never recap a used needle with two hands. Single-handed scoop technique or a device-assisted method is acceptable when recapping is absolutely necessary, but disposal without recapping is always preferred.

Drawing Up Medication

From a vial: Inject a volume of air equal to the desired medication volume into the vial to create positive pressure, then withdraw the medication. Check for air bubbles; if present, tap the syringe gently and expel them before administering.

From an ampule: Snap the neck away from you using a gauze pad. Use a filter needle to withdraw the medication — this prevents glass particles from entering the syringe. Replace the filter needle with the appropriate injection needle before administering.

Always perform three medication checks against the physician order and the medication administration record (MAR): when removing the medication from storage, when drawing it up, and at the bedside before injection.

Subcutaneous Injections

Subcutaneous injections deposit medication into the fatty tissue layer just beneath the dermis. Absorption is slower than IM but faster than oral. Common SC medications include insulin, heparin, and some vaccines.

Sites: Outer aspect of the upper arm, abdomen (avoid a 2-inch radius around the navel), anterior thigh, and upper back. Rotate sites to prevent lipodystrophy.

Needle: Typically 25–27 gauge, 5/8 inch. For thin patients or pediatric patients, a shorter needle may be appropriate.

Angle: 45 degrees for average adults; 90 degrees when the patient has generous subcutaneous tissue or when using a short needle designed for 90-degree insertion (such as many insulin syringes). Pinch the skin gently to elevate the subcutaneous layer, insert the needle, release the pinch, and inject slowly.

Aspiration: Current evidence and professional guidelines generally do not recommend routine aspiration for SC injections, particularly for insulin and heparin, because these sites lack large blood vessels. Follow facility policy.

Intradermal Injections

Intradermal injections deposit a small volume (0.01–0.1 mL) into the dermis, the layer just below the epidermis. This route is used primarily for tuberculin (TB) skin testing and allergy testing.

Site: Inner forearm is standard; the upper back may be used when the forearm is not available.

Needle: 25–27 gauge, 3/8–5/8 inch.

Angle: 5–15 degrees, bevel up. Insert just enough to place the bevel under the skin surface. Inject slowly; a pale wheal (blister-like raised area) 6–10 mm in diameter should form. If no wheal appears, the injection was too deep. Do not massage the site after an ID injection — this disperses the antigen and invalidates results.

Reading results: For TB testing (Mantoux method), results are read 48–72 hours after injection by measuring the induration (hard, raised area), not redness.

Intramuscular Injections

IM injections deliver medication into muscle tissue, which has a rich blood supply for faster absorption than SC. Volumes up to 3 mL are generally acceptable in large muscles for adults; use smaller volumes in smaller muscles.

Sites and landmarks:

Needle: 21–23 gauge; length 1–1.5 inches for most adults, adjusted for body mass.

Angle: 90 degrees.

Z-track technique: Recommended for all IM injections. Pull the skin 1–1.5 inches laterally before inserting the needle; hold it displaced during injection; wait 10 seconds after injecting, then withdraw the needle and release the skin. This seals medication in the muscle and reduces leakage, irritation, and discomfort.

Aspiration: Policies vary by facility and site. Many current guidelines, including those aligned with the CDC for vaccines, do not require aspiration at standard IM sites. However, aspiration is still recommended by some facilities for certain medications and sites. Always follow your facility's policy and the prescriber's instructions.

Documentation

Document the medication name, dose, route, site, time, and your initials on the MAR immediately after administration — never before. Record any patient response or adverse reaction in the nursing notes. Accurate documentation is a legal and professional requirement and a critical patient safety measure.

Key terms10

Subcutaneous (SC) injectionAn injection that deposits medication into the fatty tissue layer beneath the dermis, used for medications such as insulin and heparin where slower absorption is appropriate.
Intradermal (ID) injectionAn injection that deposits a very small volume of medication into the dermis, used primarily for tuberculin skin testing and allergy testing; produces a visible wheal when correctly placed.
Intramuscular (IM) injectionAn injection that delivers medication into muscle tissue, allowing faster absorption than the subcutaneous route due to the rich blood supply in muscle.
Z-track techniqueAn IM injection method in which the skin is pulled laterally before needle insertion and held displaced during injection, then released after withdrawal, sealing the medication in the muscle and reducing tissue irritation.
WhealThe pale, raised, blister-like area that should form during a correctly administered intradermal injection, indicating the medication was deposited in the dermis.
LipodystrophyAbnormal changes in fatty tissue — including lumps or hollowed areas — that can develop at injection sites when the same spot is used repeatedly without rotation.
Ventrogluteal siteAn intramuscular injection site in the gluteal area, identified using the greater trochanter and iliac crest as landmarks; considered among the safest IM sites in adults because it is distant from major nerves and blood vessels.
Filter needleA special needle with a small filter in its hub, used when drawing medication from a glass ampule to prevent glass particles from entering the syringe.
Aspiration (injection)The act of pulling back the syringe plunger after needle insertion to check for blood before injecting; current practice guidelines vary by route, medication, and facility policy.
Medication Administration Record (MAR)The legal document — paper or electronic — on which nurses record every medication given, including the name, dose, route, site, time, and administering nurse's signature.

Worked examples4

1. A patient requires 0.5 mL of a medication from a single-dose vial for a subcutaneous injection. How much air should the nurse inject into the vial before withdrawing the medication?
  1. Identify the volume of medication needed: 0.5 mL.
  2. To create positive pressure that makes withdrawal easier, inject a volume of air equal to the desired medication volume into the vial.
  3. 0.5 mL of air is drawn into the syringe first, injected into the vial, and then 0.5 mL of medication is withdrawn.
Answer: The nurse injects 0.5 mL of air into the vial, then withdraws 0.5 mL of medication.
2. The physician orders 0.1 mL of tuberculin purified protein derivative (PPD) for a Mantoux tuberculin skin test. The nurse draws up the medication and prepares to administer it intradermally on the inner forearm. At what angle should the needle be inserted, and what finding confirms correct needle placement?
  1. Recall that intradermal injections are administered at a 5–15 degree angle, bevel up, so the needle tip is just under the skin surface.
  2. Insert the needle at 5–15 degrees with the bevel facing up until the bevel is barely covered by skin.
  3. Inject the 0.1 mL slowly; correct placement in the dermis produces a pale, raised wheal approximately 6–10 mm in diameter.
  4. If no wheal forms, the needle was inserted too deeply (subcutaneous layer), and the injection must be repeated at a different site.
Answer: Insert the needle at 5–15 degrees bevel up; correct placement is confirmed by the appearance of a pale wheal 6–10 mm in diameter at the injection site.
3. A nurse is preparing 2.5 mL of an IM medication. After drawing up the medication, the nurse notices a 0.3 mL air bubble in the syringe. What volume of medication should remain in the syringe after the bubble is corrected, and how should the bubble be removed?
  1. The ordered dose is 2.5 mL of medication; air bubbles must be removed because they do not contain medication and can cause inaccurate dosing.
  2. Tap the syringe gently with a fingernail while holding it vertically with the needle pointing up to cause the bubble to rise to the top.
  3. Slowly push the plunger to expel only the air bubble out through the needle.
  4. Check that 2.5 mL of medication — and no air — remains in the syringe.
Answer: After expelling the air bubble, 2.5 mL of medication should remain in the syringe.
4. A nurse is administering an IM injection using the Z-track technique. In what order should the nurse perform the key steps of this technique?
  1. Step 1: Don gloves and cleanse the site with an alcohol swab; allow to dry.
  2. Step 2: With the non-dominant hand, pull the skin 1–1.5 inches laterally from the injection site and hold it displaced.
  3. Step 3: With the dominant hand, insert the needle at 90 degrees into the muscle.
  4. Step 4: While continuing to hold the skin displaced, inject the medication slowly; wait approximately 10 seconds after injecting.
  5. Step 5: Withdraw the needle smoothly at the same 90-degree angle, then release the displaced skin.
  6. Step 6: Apply gentle pressure if needed; do not massage. Dispose of the needle in the sharps container and document.
Answer: The correct Z-track order is: cleanse site → displace skin laterally → insert needle at 90° → inject slowly and wait → withdraw needle → release skin → apply light pressure without massaging → dispose and document.
In class: Instructor-led demonstration: drawing up a simulated medication from a vial and an ampule, selecting the correct needle gauge and length for SC, ID, and IM routes, and administering to injection pads while verbalizing rationale for each decision. · Students practice drawing up colored water from simulated vials, verifying freedom from air bubbles, then administering SC injections to injection pads at the correct 45- or 90-degree angle; they document the dose on a simulated MAR after each attempt. · Structured lab rotation: students rotate through three stations (SC abdomen pad, ID forearm pad, IM deltoid and vastus lateralis mannequin), completing each technique under peer observation with a critical-steps checklist; instructor evaluates IM station.
Materials: Injection skill pads; mannequin with IM and SC injection sites; simulated vials and ampules; colored water; syringes and needles of appropriate gauges; alcohol swabs; gloves; sharps container; simulated MARs
Check: Instructor-observed IM injection demonstration on mannequin using critical-steps checklist; all critical steps (hand hygiene, site ID, angle, aspiration policy per facility type, documentation) performed correctly for pass.

Practice check8

Answer each question, then check it. Nothing is recorded; this is your own practice.

Pharmacological and Parenteral Therapies
1. A nurse is preparing to administer an intradermal tuberculin skin test. Which needle angle is correct for this route?
Pharmacological and Parenteral Therapies
2. After administering an intradermal tuberculin skin test, the nurse notes that no wheal formed at the injection site. What is the most likely explanation?
Pharmacological and Parenteral Therapies
3. A nurse is preparing to give an intramuscular injection to an adult patient using the Z-track technique. Which action is correct?
Pharmacological and Parenteral Therapies
4. Which injection site is generally considered the safest intramuscular site for adult patients because it is located away from major nerves and blood vessels?
Pharmacological and Parenteral Therapies
5. A patient is prescribed a subcutaneous heparin injection. Which action reflects current evidence-based practice regarding aspiration for this route?
Safety and Infection Control
6. A nurse is drawing up a medication from a glass ampule. Which step is essential to prevent injury to the patient?
Pharmacological and Parenteral Therapies
7. A nurse administers a subcutaneous injection to a patient who receives daily insulin. The patient has developed hard, lumpy areas at the usual injection sites. Which nursing action addresses this finding?
Management of Care
8. When should the nurse document a medication on the medication administration record (MAR)?
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