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

• A. 0.3 mL
• B. 0.03 mL
• C. 3.0 mL
• D. 1.0 mL

Answer: (A)

Gerbils have a small circulating blood volume, roughly 6–8% of their body weight. With an animal weighing about 60–120 grams, the total blood volume is about 4–8 mL. To avoid compromising circulation, a safe rule of thumb is not to remove more than about 10% of that total in one draw, which would be around 0.4–0.8 mL. In practice, a conservative limit of 0.3 mL is used to stay safely within margins across different animals and procedures. Drawing larger amounts, like 1.0 mL or 3.0 mL, would constitute a sizable fraction of the animal’s blood and risk hypovolemia and anemia. A measurement as small as 0.03 mL would be impractically tiny for most tests.