Intramuscular Injection

What are Intramuscular Injections Used for?

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. In some cases, a person may also self-administer an intramuscular injection.

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. Intramuscular injection, often abbreviated IM, is the injection of a substance into a muscle. 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.

Intramuscular Injection Sites

The Comfort-in™ syringe/nozzle is like a transparent syringe without a needle and is used to draw a single dose of medication from a standard vial using our vial adapter. The syringe/nozzle is then attached to the Comfort-in™ injector and placed firmly against the skin at the desired injection site to administer the needle-free beauty injections. When the trigger release is pushed, Comfort-in™ delivers a fine stream of medication out of the syringe/nozzle, through the skin and into the subcutaneous tissue.

How Does it Work?

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.

Deltoid Muscle of the Arm
Vastus lateralis muscle of the thigh

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

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.

Ventrogluteal muscle of the hip


Vaccines, especially inactivated vaccines, are commonly administered via intramuscular injection. However, it has been estimated that for every vaccine injected intramuscularly, 20 injections are given to administer drugs or other therapy. This can include medications such as antibiotics, immunoglobulin, and hormones such as testosterone and medroxyprogesterone.