Subcutaneous injection: Definition and what to expect

Providers often use subcutaneous injections for medications that must be absorbed into the bloodstream slowly and steadily, such as insulin.

Subcutaneous injections are usually safe and do not require as much force as intramuscular injections into the muscle tissues.

Medications used in subcutaneous injections

Subcutaneous injection can be used to give many types of medications for various medical conditions.

There are fewer blood vessels in the fatty layer of connective tissue just beneath the skin than the muscle tissue.

Having fewer blood vessels means that medication injected subcutaneously is absorbed more slowly.

This makes it an ideal way to administer medications that the body must use slowly over time, such as insulin for the treatment of diabetes.

Medications given this way include:

  • insulin for diabetes
  • blood thinners, such as heparin
  • some fertility drugs
  • some drugs, such as Enbrel and Kineret, for autoimmune diseases, including arthritis.

Many drugs that must be taken daily, or injected at home, are designed for subcutaneous injection.

The needle used for subcutaneous injection is usually small and short and causes minimal discomfort.

The amount of pain a person feels depends on factors such as where they or another person administer the injection, their pain tolerance, and skin sensitivity.

The pain also depends on the medication they are injecting, as it may cause stinging, burning, or aching during or following the injection.

Subcutaneous injections tend to be less painful than intramuscular injections because the needles are smaller and do not have to push through as much tissue.

Children and people who fear needles may still have issues with these injections that can cause anxiety.

A few strategies can help with the pain and anxiety:

  • Use a numbing cream on the area a few minutes before the injection. Many doctor’s offices have these available.
  • Try putting ice on the area to numb it a few minutes before the injection.
  • Allow nursing babies to breast-feed during injections.
  • If a child needs restraining, hold them in a hugging way rather than holding them down or yelling at them.
  • Give a baby a pacifier before an injection.
  • Cough or blow before or during the injection.
  • Take five deep breaths or encourage children to breathe deeply before the shot.
  • Distract yourself with a movie, video game, or conversation. Sometimes looking at the shot makes it hurt more.

Are there any complications?

The most common complication of a subcutaneous injection is pain near the injection site for 1 to 2 days afterward.

Pain near the injection site can happen when inserting the needle at the wrong angle, or when it moves slightly during the injection. Some medications can cause a bruise or irritation at the injection site.

Other complications are much less frequent and include:

  • Infection: Any puncture in the skin can allow bacteria to enter and cause an infection. Properly cleaning the area and always using a clean needle can reduce the risk of infection.
  • Contaminated needle: Reusing needles or sharing needles can spread diseases from one person to another. Always dispose of used needles in an appropriate container.
  • Injecting medication into a blood vessel: A person may have hit a blood vessel if there is blood in the syringe. Injecting medication into a blood vessel can change the way the drug is absorbed.

Injecting a blood vessel can cause serious complications in rare cases. However, the likelihood of hitting a blood vessel in the subcutaneous fat is extremely rare. More than likely, if there is blood, it is from slight bleeding after the injection.


A subcutaneous injection is a minor and very safe medical procedure when done correctly.

Mastering the technique of injecting at home can take some practice. People should ask for help from a medical provider and not shy away from asking questions about the benefits of treatment or how best to minimize pain.

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