Intraperitoneal injections in mice are typically administered in which anatomical area?

• A. Lower right quadrant near midline
• B. Left forelimb muscle
• C. Subcutaneous tissue in scruff
• D. The tail vein

Answer: (A)

Intraperitoneal injections place the substance into the peritoneal cavity, so the aim is to access that space safely and consistently. The lower right quadrant near the midline is picked because it provides a window into the peritoneal space that minimizes the risk of puncturing solid organs or major vessels. It’s a location where the abdominal wall is accessible and the viscera aren’t usually in the way, making it easier to deliver the dose into the cavity rather than into muscle or a blood vessel. The other options correspond to different routes—subcutaneous in the scruff, intramuscular in the muscle, or intravenous via the tail vein—so they’re not intraperitoneal injections.