What is the maximum volume of blood that can safely be taken from a mouse?

• A. 0.14 mL
• B. 1.4 mL
• C. 0.014 mL
• D. 1.0 mL

Answer: (A)

The key idea is safety by proportional blood collection. For small animals like mice, you don’t take a fixed amount; you limit sampling to about 10% of the animal’s total blood volume to avoid hypovolemia. A mouse has roughly 6–7% of its body weight in blood; for a typical 25 g mouse that’s about 1.5 mL of blood total. Ten percent of that is about 0.15 mL, so a single safe draw is around 0.14 mL. Any larger volume would risk significant blood loss and distress, while smaller volumes would be unnecessary for many tests. If multiple samples are needed, you must divide the total permissible volume across draws with adequate intervals to protect the animal.