Final answer:
Subcutaneous injection requires the needle to be inserted at a 45 degree angle to the skin.
Step-by-step explanation:
The form of injection that requires the needle to be inserted at a 45 degree angle to the skin is subcutaneous injection.
Subcutaneous injection is a technique of administering medication into the layer of fat located beneath the skin. It is usually done at a 45 degree angle, and the drug is injected into the subcutaneous tissue.
Examples of subcutaneous injection include administering insulin and certain vaccines, such as the flu shot.