This type of injection is used when other methods of administration might be less effective.
Subcutaneous injection is a method of injecting medication into the subcutaneous tissue, the layer of fat right under the skin. A short needle is used to inject a medicine into the tissue layer between the skin and muscle. Medication administered this way is usually absorbed more slowly compared with when injected into the vein, sometimes even over a period of 24 hours. This type of injection is used when other methods of administration might be less effective. For example, some medications can’t be taken orally because they may get destroyed by digestive enzymes. Subcutaneous injections are quick and easy to administer. It can be administered by the individual themselves or their caregiver. Other methods of injection, such as intravenous or intramuscular injections, can be difficult and expensive for regular use. Only certain medications in prescribed doses can be injected subcutaneously; hence, it is advised to consult a doctor and not self-medicate.
The site of subcutaneous injection is important. The site where a subcutaneous injection is given should contain sufficient fatty tissue to avoid the needle hitting a muscle, bone, or blood vessel.
The most common sites to administer a subcutaneous injection include:
- Abdomen (at or under the level of the belly button, about 2 inches away from the navel)
- Thigh (front of the thigh or inner thighs)
- Arm (the back or side of the upper arm with sufficient subcutaneous fatty tissue)
What medications can be given using a subcutaneous injection?
Medications injected by a subcutaneous injection are usually medications that can be given in small volumes (up to 2 mL). Some common medications include:
- Insulin may be administered using the traditional insulin syringe or in the form of an automated injector, insulin pen.
- Hormones for hormone therapy
- Fertility medication
- Epinephrine to treat allergic reactions. It comes in an automated injector form called the EpiPen. It can also be given intramuscularly (injected into the muscles).
- Steroid medication such as dexamethasone to suppress inflammation
- Allergy shots
- Blood thinners
- Pain medications such as morphine
- Anti-nausea and anti-vomiting medications such as metoclopramide
- Certain vaccines
How is a subcutaneous injection given?
Equipment used for subcutaneous injections includes:
- Syringes: The needles are typically short, around 5/8-inch long, and thin with usually a capacity of 1 mL and sometimes more for children and people with visual difficulties.
- Auto-injector pen: Some medications such as epinephrine and insulin are available in the form of a “pen” with a multi-use vial, which is quick and easy to administer, making it beneficial during emergencies.
- Medication
Before injection:
The individual or caregiver should first wash their hands thoroughly or use an alcohol-based hand sanitizer. Following this, all the supplies required should be gathered, such as the syringe or auto-injection pen, alcohol swabs, some cotton or gauze, and a band-aid.
The injection site should be disinfected using an alcohol swab. The injection site should not have any swelling, redness, bruising, hardness, change in the skin texture or color, irritation, pain, or dilated veins. If these abnormalities are present, an alternate injection site may be chosen. To prevent damage to an area as a result of repeated injections at the same site, it is advised to change the injection site often. The syringe should then be loaded with medication. In the case of an auto-injection pen, this is not required every time, and the vial needs to be changed once it’s completely over. It’s advised to follow the dosage advised by the doctor accurately. A new needle is required for the syringe with every injection. The auto-injection pen can be reused by the same person with the same needle. The needle may be disinfected using an alcohol-based disinfectant.
During injection:
Once the appropriate site of injection is identified, the skin should be pinched between the thumb and index finger (around an inch and a half apart) and held in that position till the procedure is completed. This pulls the fatty tissue away from the underlying muscle, making the injection safer and easier. The needle should be held at an angle of 90° or at an angle of 45° if the person is thin with very little fat. This should be done quickly, without applying too much force. The entire medication loaded in the syringe with the prescribed dose should be slowly pushed into the pinched injected site. The pinched skin can be released as the needle is withdrawn. Mild pressure may be applied after the injection to prevent bleeding. There is usually no more than one to two drops of blood loss during a subcutaneous injection. There may be minimal swelling and bruising, which resolves on its own. Subcutaneous injections should not be administered in the same spot twice in a row to avoid complications. A subcutaneous injection is not very painful and feels like a quick pin prick or ant bite lasting a few seconds. It is advised to have a healthcare professional demonstrate how to administer the injection before one attempts to administer it themselves.