Which is an appropriate technique for subcutaneous injections in mice?

• A. Inject into the muscle of the hind leg
• B. Insert the needle into the tail vein
• C. Lift the skin on the back of the mouse, and insert the needle into the base of the tent.
• D. Pinch the skin and inject into the shoulder blade

Answer: (C)

Subcutaneous injections deliver fluid into the loose tissue just beneath the skin. For mice, the most reliable method is to lift the skin on the back to form a small tent and insert the needle at the base of that tent. This places the needle tip under the skin in the subcutaneous space, allowing the solution to be absorbed there without entering muscle or a blood vessel. The back skin forms a convenient, loose pocket that’s easy to access, making this technique straightforward and less traumatic for the animal.

In contrast, injecting into the muscle of the hind leg is an intramuscular route, not subcutaneous. Inserting the needle into the tail vein would be an intravenous route, bypassing the subcutaneous space entirely. Pinching the skin and injecting into the shoulder blade isn’t the standard subcutaneous pocket and can risk hitting muscle or other tissues, making it less reliable for subcutaneous administration.