A small amount of blood can be obtained by cutting a toenail. If larger amounts are needed, here is an easy procedure that makes it possible to collect up to 3 ml of blood. (Only 1 ml should be collected per 100 g [about ¼ lb] of the rat’s body weight.)
Restrain the rat in a burrito. Depending on how much blood you need, hold a warm washcloth around the tail for about 30 seconds, or soak the tail in warm water for 5 minutes to stimulate blood flow. Make a nick on one side of the tip of the tail with a scalpel or razor blade (this will hurt for just an instant, like getting your finger stuck). Let the tail hang down over the edge of the table. Catch the blood droplets which come from the tip in a blood tube. If necessary, the tail can be “milked” to get more blood, but this may change the numbers of cells and affect the results of the tests. To stop the bleeding, elevate the tail and apply pressure and ice to the tip.
There is a video on You Tube that shows how to collect blood from the tip of the tail for a blood glucose test at https://youtu.be/yBAg8ajwpU0
The Rat Burrito
For easy access to your rat’s tail, make a rat burrito. Place him in the center of a small towel and fold half over his head. Then quickly fold the towel around him, leaving his tail hanging out. The tighter you wrap your rat, the calmer he will be. You can secure the towel around him with safety pins.
Making a rat burrito.
Rat Fan Club