Intraperitoneal injection


Intraperitoneal Graphic

  1. First locate the point of entry for the needle.
  2. Draw an imaginary line across the abdomen just above the knees (see image above).
  3. The needle will be inserted along this line on the animal’s right side and close to the midline.
  4. As this is a female, you can see that the point of entry is cranial to and slightly medial of the last nipple.
  5. Inserting the needle on the mouse’s right side avoids the cecum, which is a large fluid-filled organ on the left side of the abdomen. The small intestines (on the right side) are less likely to be punctured by the needle.
  6. Inserting the needle too far caudally or laterally from the insertion point shown above would risk making an injection into the rear leg which would injure the muscle tissue.
  7. To perform an IP injection, the mouse must be well restrained so that it cannot move during the procedure. This avoids traumatizing the organs once the needle has entered the abdomen.
  8. Restrain the mouse and tilt so that the head is facing downward and its abdoment is exposed.
  9. Insert the needle into the abdomen at about a 30-degree angle after disinfecting injection site..
  10. The shaft of the needle should enter to a depth of about half a centimeter.
  11. Aspirate to be sure that the needle has not penetrated a blood vessel, the intestines, or the urinary bladder.
  12. Greenish brown aspirate indicates needle penetration into intestines.
  13. Yellow aspirate indicates needle penetration into the bladder
  14. If any fluid is aspirated, your solution is contaminated and must be discarded and the procedure repeated with a new syringe and needle.
  15. If no fluid is aspirated, you may inject.
  16. Withdraw the needle and return the mouse to its cage.

The recommended needle size for IP injections in the mouse is 25-27 gauge.


Procedure same as in the mouse.  The recommended needle size for IP injections in the rat is 25 gauge.

Information from AALAS learning Library