What Are Intramuscular Injections?

Medically reviewed by Deborah Weatherspoon, PhD, RN, CRNA on August 11, 2017 — Written by Jacquelyn Cafasso


An intramuscular injection is a technique used to deliver a medication deep into the muscles. This allows the medication to be absorbed into the bloodstream quickly. You may have received an intramuscular injection at a doctor’s office the last time you got a vaccine , like the flu shot .

In some cases, a person may also self-administer an intramuscular injection. For example, certain drugs that treat multiple sclerosis or rheumatoid arthritis may require self-injection.

What are intramuscular injections used for?

Intramuscular injections are a common practice in modern medicine. They’re used to deliver drugs and vaccines. Several drugs and almost all injectable vaccines are delivered this way.

Intramuscular injections are used when other types of delivery methods aren’t recommended. These include:

  • oral (swallowed into the stomach )
  • intravenous (injected into the vein)
  • subcutaneous (injected into the fatty tissue just under the layer of skin)

Intramuscular injections may be used instead of intravenous injections because some drugs are irritating to veins, or because a suitable vein can’t be located. It may be used instead of oral delivery because some drugs are destroyed by the digestive system when a drug is swallowed.

Intramuscular injections are absorbed faster than subcutaneous injections . This is because muscle tissue has a greater blood supply than the tissue just under the skin. Muscle tissue can also hold a larger volume of medication than subcutaneous tissue.

injection sites

Intramuscular injections are often given in the following areas:

Deltoid muscle of the arm

The deltoid muscle is the site most typically used for vaccines. However, this site is not common for self-injection, because its small muscle mass limits the volume of medication that can be injected — typically no more than 1 milliliter.

It’s also difficult to use this site for self-injection. A caregiver, friend, or family member can assist with injections into this muscle.

To locate this site, feel for the bone (acromion process) that’s located at the top of the upper arm. The correct area to give the injection is two finger widths below the acromion process. At the bottom of the two fingers, will be an upside-down triangle. Give the injection in the center of the triangle.

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Vastus lateralis muscle of the thigh

The thigh may be used when the other sites aren’t available or if you need to administer the medication on your own.

Divide the upper thigh into three equal parts. Locate the middle of these three sections. The injection should go into the outer top portion of this section.

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Ventrogluteal muscle of the hip

The ventrogluteal muscle is the safest site for adults and children older than 7 months. It’s deep and not close to any major blood vessels and nerves. This site is difficult for self-injection, and may require the help of a friend, family member, or caregiver.

Place the heel of your hand on the hip of the person receiving the injection, with the fingers pointing towards their head. Position the fingers so the thumb points toward the groin and you feel the pelvis under your pinky finger. Spread your index and middle fingers in a slight V shape, and inject the needle into the middle of that V.

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Dorsogluteal muscles of the buttocks

The dorsogluteal muscle of the buttocks was the site most commonly selected by healthcare providers for many years. However, due to the potential for injury to the sciatic nerve , the ventrogluteal is most often used now. This site is difficult to use this site for self-injection and not recommended.

You shouldn’t use an injection site that has evidence of infection or injury. If you’ll be giving the injection more than once, make sure to rotate injection sites to avoid injury or discomfort to the muscles.

to administer an intramuscular injection

Any person who administers intramuscular injections should receive training and education on proper injection technique.

The needle size and injection site will depend on many factors. These include the age and size of the person receiving the medication, and the volume and type of medication. Your doctor or pharmacist will give you specific guidelines about which needle and syringe are appropriate to administer your medication.

The needle should be long enough to reach the muscle without penetrating the nerves and blood vessels underneath. Generally, needles should be 1 inch to 1.5 inches for an adult, and will be smaller for a child. They’ll be 22-gauge to 25-gauge thick, noted as 22g on the packaging.

Follow these steps for a safe intramuscular injection:

1) Wash your hands

Wash your hands with soap and warm water to prevent potential infection. Be sure to thoroughly scrub between fingers, on the backs of hands, and under fingernails.

The Centers for Disease Control and Prevention (CDC) recommends lathering for 20 seconds — the time it takes to sing the “Happy Birthday” song twice.

2) Gather all needed supplies

Assemble the following supplies:

  • needle and syringe with medication
  • alcohol pads
  • gauze
  • puncture-resistant container to discard the used needles and syringe — typically a red, plastic sharps container
  • bandages

3) Locate injection site

To isolate the muscle and target where you’ll place the injection, spread the skin at the injection site between two fingers. The person receiving the injection should get into a position that’s comfortable, provides easy access to the location, and keeps the muscles relaxed.

4) Clean injection site

Clean the site selected for injection with an alcohol swab and allow the skin to air dry.

5) Prepare syringe with medication

Remove the cap. If the vial or pen is multi-dose, take a note about when the vial was first opened. The rubber stopper should be cleaned with an alcohol swab.

Draw air into the syringe. Draw back the plunger to fill the syringe with air up to the dose that you’ll be injecting. This is done because the vial is a vacuum and you need to add an equal amount of air to regulate the pressure. This also makes it easier to draw the medication into the syringe. Don’t worry — if you forget this step, you can still get the medication out of the vial.

Insert air into the vial. Remove the cap from the needle and push the needle through the rubber stopper at the top of the vial. Inject all of the air into the vial. Be careful to not touch the needle to keep it clean.

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Withdraw the medication. Turn the vial and syringe upside down so the needle points upward and pull back on the plunger to withdraw the correct amount of medication.

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Remove air bubbles. Tap the syringe to push any bubbles to the top and gently depress the plunger to push the air bubbles out.

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6) Self-injection with a syringe

Insert the needle. Hold the needle like a dart and insert it into the muscle at a 90-degree angle. You should insert the needle in a quick, but controlled manner. Do not push the plunger in.

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Check for blood. Using the hand that’s holding the skin at the injection site, pick up your index finger and thumb to stabilize the needle. Use your dominant hand — the one that did the injection — to pull back on the plunger slightly, looking for blood in the syringe. Ask your doctor if this is needed for the type of medicine you will be injecting, as it’s not required for all injections.

  • If you see blood going into the syringe, it means the tip of the needle is in a blood vessel. If this happens, withdraw the needle and begin again with a new needle, syringe with medication, and injection site. It’s rare to have this happen.
  • If you don’t see blood going into the syringe, the needle is in the correct place and you can inject the medicine.

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7) Inject the medication

Push the plunger slowly to inject the medication into the muscle.

8) Remove the needle

Withdraw the needle quickly and discard it into a puncture-resistant sharps container. Don’t recap the needle.

A sharps container is a red container that you can purchase at any pharmacy. It’s used to collect medical waste, like needles and syringes. You shouldn’t put any of these materials into the regular garbage, as needles can be hazardous to anyone who handles the trash.

9) Apply pressure to the injection site

Use a piece of gauze to apply light pressure to the injection site. You can even massage the area to help the medicine be absorbed into the muscle. It’s normal to see slight bleeding. Use a bandage if necessary.

for an easier injection

To minimize possible discomfort before your injection:

  • Apply ice or an over-the-counter topical numbing cream to the injection site before cleaning it with the alcohol pad.
  • Allow the alcohol to dry completely before the injection. Otherwise, it might cause stinging.
  • Warm the vial of medication by rubbing it between your hands prior to drawing the medication into the syringe.
  • Have someone you trust give you the injection. Some people find it difficult to inject themselves.

are the complications of intramuscular injections?

It’s normal to experience some discomfort after an intramuscular injection. But certain symptoms may be a sign of a more serious complication. Call your doctor or healthcare provider right away if you experience:

  • severe pain at the injection site
  • tingling or numbness
  • redness , swelling , or warmth at the injection site
  • drainage at the injection site
  • prolonged bleeding
  • signs of an allergic reaction , such as difficulty breathing or facial swelling

It’s also normal to have some anxiety about performing or receiving an injection, especially an intramuscular injection due to the long needle. Read through the steps several times until you feel comfortable with the procedure, and take your time.

Don’t hesitate to ask your provider or pharmacist to go through the procedure with you beforehand. They’re more than willing to help you understand how to perform a safe, proper injection.

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Medically reviewed by Deborah Weatherspoon, PhD, RN, CRNA on August 11, 2017 — Written by Jacquelyn Cafasso

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Clinical Practice – IM injections: How’s your technique?

Good injection technique can mean the difference between less pain and injury. Angela Cocoman and John Murray explain

The administration of intramuscular injections is a common nursing intervention in clinical practice.1 This article aims to, raise awareness in relation to the injection sites used for intramuscular injection and, to highlight best practice in relation to IM injection administration.

The importance of good injection technique cannot be understated. It should not be forgotten that among potential complications of IM injection are abscess, cellulites, tissue necrosis, granuloma, muscle fibrosis, contractures, haematoma and injury to blood vessels, bones and peripheral nerves.2 Although IM injection is a commonplace nursing practice, there is a dearth of guidelines for nursing staff in this area.3,4 It has been outlined that there are no working policies or procedures on administering injections to which nursing staff can refer.3 Furthermore, the technique and preparation by certain staff may not be substantiated by evidence.4

Sites of the thigh (Rectus femoris and Vastus lateralis)
The uptake of drugs from the thigh region is slower than from the arm but faster than from the buttock, thus facilitating better drug serum concentrations than is possible with the gluteal muscles.5

Giving an IM injection into the Vastus lateralis site

  • To find the thigh injection site, make an imaginary box on the upper leg. Find the groin. One hand’s width below the groin becomes the upper border of the box
  • Find the top of knee. One hand’s width above the top of the knee becomes the lower border of the box
  • Stretch the skin to make it tight
  • Insert the needle at a right angle to the skin (90°) straight in
  • Up to 2ml of fluid may be given into this site

The thigh may be utilised when other sites are contraindicated or by clients who administer their own medication, as it is readily available in the sitting or lying back position. However, the main disadvantage is that injections in the Rectus femoris site may cause considerable discomfort.6

This site can be used for infants, children and adults. Needle length used is usually 2.5cm or less.

The dorsogluteal site
This site is commonly referred to as the outer upper quadrant and is contraindicated in children.

IM injection into the Gluteus medius site (buttock)

  • Find the trochanter. It is the knobbly top portion of the long bone in the upper leg (femur). It is the size of a golf ball
  • Find the posterior iliac crest. Many people have ‘dimples’ over this bone
  • Draw an imaginary line between the two bones
  • After locating the centre of the imaginary line, find a point one inch toward the head. This is where (X) to insert the needle
  • Stretch the skin tight
  • Hold the syringe like a pencil or dart. Insert the needle at a right angle to the skin
  • Up to 3ml of fluid can be given in this site

The presence of major nerves and blood vessels, the relatively slow uptake of medication from this site compared with others and the thick layer of adipose tissue commonly associated with it, makes this site problematic.7 The sciatic nerve and superior gluteal artery lie only a few centimetres distal to the injection site, thus great care needs to be taken to identify landmarks accurately. Palpating the ileum and the trochanter is important; using visual calculations alone can result in injection being placed too low and injuries to other structures.8

Risks associated with an IM injection to the dorsogluteal site

  • Contact with sciatic nerve
  • Contact with the superior gluteal artery
  • Too much fatty tissue – poor absorption rates.

The deltoid site
The ease of access, especially in an outpatient setting, possibly adds to the frequency with which the deltoid site is used for IM injections. This site is used for immunisations/non-irritating medications, hence vaccines which are usually small in volume tend to be administered into the deltoid site.9 This is a relatively small area and muscle mass, especially in atrophied patients compounded by the close proximity of the radial nerve, brachial artery and bony processes to this site means that more substantial injuries can occur.

Giving an IM injection into the deltoid site

  • Find the knobbly top of the arm (acromion process)
  • The top border of an inverted triangle is two finger widths down from the acromion process
  • Stretch the skin and then bunch up the muscle
  • Insert the needle at a right angle to the skin in the centre of the inverted triangle

Caution: This is a small site – give only 1-2ml or less of fluid in this site

It is important to limit volume of medication based upon size of muscle, ie. 0.5-2ml.

The ventrogluteal site
The Ventrogluteal site provides the greatest thickness of gluteal muscle (consisting of both the gluteus medius and gluteus minimus), is free of penetrating nerves and blood vessels, and has a narrower layer of fat of consistent thinness than is present in the dorsogluteal.10

The ventrogluteal site has come to attract significant attention in the nursing literature and there is wide agreement that this site is the preferable site for intramuscular injection.2 There is a dearth of research in this area in Ireland as to the extent to which the ventrogluteal site is used.

Giving an IM injection into the ventrogluteal site

  • Find the trochanter. It is the knobbly top portion of the long bone in the upper leg (femur). It is about the size of a golf ball

  • Find the anterior iliac crest

  • Place the palm of your hand over the trochanter. Point the first or index finger toward the anterior iliac crest. Spread the second or middle finger toward the back, making a ‘V’. The thumb should always be pointed toward the front of the leg. Always use the index finger and middle finger to make the ‘V’

  • Give the injection between the knuckles on your index and middle fingers

  • Stretch the skin tight

  • Hold the syringe like a pencil or dart. Insert the needle at a right angle to the skin (90°)

  • Up to 3ml of fluid may be given in this site7

Administrating an IM injection
There is a large research base for nursing practice to be guided by in relation to the administration of intramuscular injections and it is the responsibility of nurse educators to ensure that appropriately informed guidelines are devised.4

Tracking technique: An intramuscular injection is
designed to deposit medications deep into muscle tissue

It has been suggested4 that the following points should be incorporated into clinical guidelines:

  • IM injections should be administered in the Ventrogluteal region whenever possible
  • The medication should be administered with a needle long enough to reach the muscle without penetrating underlying structures
  • The patient should be positioned so as to relax the muscle
  • The ‘Z track’ technique should be used at all times (see diagram).

These measures should ensure optimal nursing care for patients.

Angela Cocoman is mental health lecturer at DCU and John Murray is a community mental health nurse for Water ford Mental Health Services (HSE South Eastern Area)


  1. Greenway K. Using the ventral gluteal site for intramuscular injection. Nursing Standard 2004; 18 (29): 39-42
  2. Small SP. Preventing sciatic nerve injury from intramuscular injection: literature review: J Advanced Nursing 2004; 47(3): 287-296
  3. MacGabhan L. A comparison of two depot injection techniques. Nursing Standard 1996; 11(52): 33-37
  4. McGarvey MA. Intramuscular injections: a review of nursing practice for adults. All Ireland J Nursing & Midwifery 2001; 1(5): 185-193
  5. Newton M, Newtown DW, Fudin J. Reviewing the big three injection routes. Nursing 1992; 22: 34-42
  6. Berger KJ, Williams MS. Fundamentals of Nursing: Collaborating for Optimal Health. Appletone Large: Connecticut, 1992
  7. Bolander VR. Sorenson & Luckmann’s Basic Nursing, A Psychophysiological Approach (3rd ed.) Saunders: Philadelphia, 1994
  8. Kozier et al. Techniques in Clinical Nursing (4th ed). Sage: California, 1993
  9. Mallett J, Bailey C. The Royal Marsden NHS Trust Manual of Clinical Procedures (5th ed.) Blackwell Science: London, 1996
  10. Zelman S. Notes on the techniques of intramuscular injection. Am J Med Sc 1961; 241: 47-58
  11. Rodger MA, King L. Drawing up and administering intramuscular injections: a review of literature. J Advanced Nursing 2000; 31(3): 574-582

 Clinical Practice – IM injections: How’s your technique?


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