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Intramuscular Administration

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By Paul Martin, BSN, R.N.

Intramuscular injection (IMI) delivers medication deep into muscle tissue, allowing rapid absorption due to the muscle’s good vascularization. This route also accommodates larger medication volumes compared to alternative administration routes.

While often viewed as a simple nursing procedure, improper technique and inadequate knowledge of correct injection sites can lead to numerous serious complications. This guide aims to educate on the different injection sites, proper technique, and what to monitor after IM administration.

Table of Contents

What is Intramuscular Administration?

Intramuscular administration involves injecting medication directly into the muscle tissue. This method allows the drug to be absorbed into the bloodstream more rapidly than subcutaneous injections, but not as quickly as intravenous injections. It is often used for vaccines, antibiotics, and certain other medications that need to be absorbed quickly and efficiently.

Intramuscular Injection Sites

There are several common sites for intramuscular injections, including:

  • Deltoid muscle. It is typically used for small medication volumes (2 ml or less) and is a common injection site for routine adult immunizations. It is located two finger widths below the acromion process.
  • Vastus lateralis muscle. It is the preferred intramuscular (IM) injection site for neonates and infants. It is located on the anterior lateral aspect of the thigh. In adults, it stretches from a handbreadth above the knee to a handbreadth below the greater trochanter of the femur. Injections are administered in the middle third of this muscle.
  • Ventrogluteal muscle (gluteus medius and minimus muscles). It is considered the safest injection site for adults and children over 7 months of age due to its thick muscle layer, lack of major nerves and blood vessels, and minimal fat. It is the preferred site for medications requiring larger volumes.
  • Dorsogluteal muscle. Located in the buttocks, it is less commonly used due to the potential risk of injury to the sciatic nerve.


The advantages of IM administration lie in its ability to achieve rapid medication uptake and effectiveness through direct injection into muscle fibers.

  • Rapid absorption. Medications administered via IM injection are absorbed quickly and evenly into the bloodstream through well-vascularized muscle tissue faster than with subcutaneous injections.
  • Rapid onset. Compared to oral and subcutaneous routes, IM injections offer a faster onset of action due to direct delivery into muscle tissue.
  • Larger volume: IM injections can accommodate larger volumes of medication compared to subcutaneous injections.
  • Bypassing first-pass metabolism. IM injections bypass the first-pass metabolism in the liver, allowing for higher bioavailability of the drug compared to oral administration. This route ensures that a larger proportion of the drug reaches systemic circulation unchanged.
  • Longer Duration: Provides a longer duration of action for some medications compared to intravenous administration.
  • Targeted Delivery: Allows for the targeted delivery of medication to specific muscle groups.


IM administration may pose challenges due to the potential for discomfort during injection and the need for careful site selection to avoid injury.

  • Need expertise and training. Improper administration by untrained individuals can lead to injection site reactions, inadequate drug absorption, or inadvertent injuries.
  • Painful procedure. IM injections can be painful, especially in sensitive individuals or when administered in muscles with fewer pain-reducing nerve endings. Pain during injection can cause patient distress, reluctance to undergo subsequent injections, and reduced compliance with treatment regimens.
  • Absorption is dependent on muscle bulk and vascularity. Variations in muscle bulk and blood flow can affect the consistency and predictability of drug absorption, influencing the drug’s onset and duration of action.
  • Risk of inadvertent subcutaneous injection. Accidental injection into the subcutaneous tissue instead of the muscle can delay drug absorption and action. This error may result in reduced therapeutic effectiveness, prolonged onset of action, and patient dissatisfaction due to delayed symptom relief.
  • Difficulty in self-administration. Patients may require assistance from healthcare professionals, increasing dependency on medical assistance for routine medication administration.
  • Delayed release of medications from the muscular compartment. This can result in unintended prolonged sequelae, such as prolonged side effects or delayed therapeutic benefits. This delay may complicate patient management and require close monitoring and intervention.


Common complications:

  • Pain and discomfort. Pain and discomfort at the injection site are common complications. This can be due to the medication itself, the needle size, or the injection technique.
  • Abscess formation. This can occur if the injection is not performed under sterile conditions or if bacteria are introduced during the injection process.
  • Nerve injury. Nerve injury can occur if the needle strikes a nerve during the injection. This can result in pain, numbness, or even paralysis in severe cases. The sciatic nerve is particularly at risk with dorsogluteal injections.
  • Muscle fibrosis. Repeated injections in the same site can cause muscle tissue damage, leading to fibrosis or the formation of scar tissue.
  • Hematoma formation. A hematoma is a localized collection of blood outside the blood vessels, which can occur if a blood vessel is punctured during the injection. This results in bruising and swelling.
  • Lipodystrophy. Lipodystrophy involves changes in the fat tissue under the skin, which can result from repeated injections at the same site. This can cause lumps or indentations in the skin.

How to administer intramuscular injections?

Correctly preparing and administering an IM injection involves following these steps:

1. Wash hands thoroughly and wear appropriate personal protective equipment (PPE) depending on whether the patient requires isolation precautions or is at risk of exposure to bodily fluids. This is done to prevent the transmission of microorganisms and to protect both nurses and patients from infections.

2. Collect all necessary items (syringe, needle, medication, alcohol swabs, gloves).

  • Appropriate size needle for administration
    • Use large-bore needles (18 and 20 gauge) for thick, viscous medications.
    • Use small-bore needles (22 and 25 gauge) for thinner medications and when administering to infants.
  • Drawing up needle and syringe (if medication not pre-filled)
  • Sharps container
  • Alcohol swab
  • Cotton ball
  • Band-Aid (check for allergies)
  • Personal Protective Equipment (PPE) for hazardous medications or infectious patients

3. Position the client appropriately based on the injection site chosen. For the ventrogluteal site (gluteus medius muscle), place the client in a supine position with knees flexed, lateral position with upper leg flexed, or prone position with toes held. Position the patient comfortably to ensure muscle relaxation and facilitate easy access to the injection site.

4. Choose the appropriate site based on the volume and type of medication.

  • Infants (0-12 months)
    • Preferred Site: Vastus lateralis (thigh)
    • Volume: Up to 1 mL
    • Types of Medications: Vaccinations, antibiotics
  • Children (1-12 years)
    • Preferred Site: Vastus lateralis (thigh) or deltoid (upper arm)
    • Volume: Up to 2 mL in vastus lateralis; up to 1 mL in deltoid
    • Types of Medications: Vaccinations, antibiotics, hormone treatments
  • Adolescents (13-18 years)
    • Preferred Site: Deltoid (upper arm), ventrogluteal (hip), or vastus lateralis (thigh)
    • Volume: Up to 3 mL in ventrogluteal and vastus lateralis; up to 2 mL in deltoid
    • Types of Medications: Vaccinations, antibiotics, hormone treatments, certain types of pain medications
  • Adults (18 years and older)
    • Preferred Site: Ventrogluteal (hip), deltoid (upper arm), or vastus lateralis (thigh)
    • Volume: Up to 5 mL in ventrogluteal and vastus lateralis; up to 3 mL in deltoid
    • Types of Medications: Antibiotics, hormone treatments, certain types of pain medications, depot injections

5. Use an alcohol swab to clean the injection site in a circular motion from the center outward to prevent infection. Cleaning the injection site with an alcohol swab in a circular motion from the center outward minimizes microbial load, lowering the risk of infection at the injection site.

6. Draw the medication into the syringe, ensuring there are no air bubbles. If using a prefilled unit-dose medication, take extra caution to prevent any medication from dripping onto the needle before injection. Ensures accurate dosing, maintains sterility, and minimizes the risk of contamination during injection.

7. Remove the needle cap by pulling it straight off the needle. Hold the syringe with your dominant hand between your thumb and forefinger, as if holding a dart. This provides a stable grip that enhances control during the injection process.

8. With the non-dominant hand, pull the skin laterally, creating tension and displacing subcutaneous tissue away from the muscle (Z-track method). This helps prevent medication leakage and ensures the needle penetrates deep into the muscle tissue, lowering the risk of tissue irritation or subcutaneous leakage of the medication post-injection.

9. With the dominant hand, using a steady and smooth motion, insert the needle at a 90-degree angle into the muscle. Using a steady and smooth motion minimizes patient’s discomfort.

10. After the needle pierces the skin, use the thumb and forefinger of the non-dominant hand to hold the syringe. This reduces the risk of accidental movement or improper placement of the needle.

11. Aspirate (depending on agency protocol), Pull back on the plunger slightly to check for blood. If no blood appears, inject the medication slowly and steadily. However, If blood appears, remove the needle and choose a new site. Aspiration checks for inadvertent intravascular placement of the needle, confirming that medication is injected into the muscle tissue rather than into a blood vessel, which could lead to unintended systemic effects or complications.

12. Upon completion of the injection, withdraw the needle smoothly and steadily, maintaining the original insertion angle. This minimizes tissue trauma and discomfort at the injection site.

13. Apply gentle pressure to the injection site with a cotton ball or gauze. This helps to prevent any bleeding at the injection site

14. Place a safety shield on the needle and discard the syringe in a sharps container. Promotes safe handling and disposal to prevent accidental needle-stick injuries and contamination.

15. Record the administration details in the patient’s medical records. Ensures thorough documentation to maintain treatment continuity, aid provider communication, and track medication history for patient safety and legal compliance.

Nursing Considerations

These practices help ensure safe and effective administration of IM injections, promoting patient comfort and lessening complications.

1. Monitor for immediate adverse reactions such as fever, rash, vomiting, or difficulty breathing. These symptoms could indicate an allergic or anaphylactic reaction that requires prompt medical attention.

2. Use proper needle size. Select a needle gauge appropriate for the viscosity of the medication and the patient’s age and muscle mass.

3. Separate injection sites when administering multiple vaccines in the same arm. This practice minimizes local reactions like swelling, redness, or discomfort at injection sites.

4. Allow the alcohol to dry completely before the injection. Complete drying ensures clean, dry skin and minimizes stinging from residual alcohol.

5. Apply warm or cold compresses at the injection site. Warm compresses can soothe soreness or muscle pain, while cold compresses can reduce swelling and inflammation.

6. Teach comfort measures when IM injections are administered to children/infants. Nonpharmacologic comfort measures such as positioning, breastfeeding, and distraction may help minimize anxiety and discomfort, promoting a more positive experience and cooperation during the procedure.

7. Avoid massaging the area at the site of injection. Massaging the site can lead to medication leakage and subsequent irritation.

8. Avoid administering IM injections into the dorsogluteal muscle. This is recommended due to the potential risk of hitting blood vessels, nerves, or bones in this area, which can lead to complications such as hematoma, nerve injury, or improper medication absorption.

Sources and References

Paul Martin R.N. brings his wealth of experience from five years as a medical-surgical nurse to his role as a nursing instructor and writer for Nurseslabs, where he shares his expertise in nursing management, emergency care, critical care, infection control, and public health to help students and nurses become the best version of themselves and elevate the nursing profession.

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