The subcutis is the layer of tissue directly underlying the cutis. It is mainly composed of adipose tissue. Its physiological function includes insulation and storage of nutrients. Directly below the subcutis is usually a layer of muscle (covered in a fascia) or bone (covered in periosteum).

Subcutaneous injections are given by injecting a fluid into the subcutis. It is relatively painless and an effective way to administer particular types of medication.