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

• A. 0.13 mL
• B. 1.3 mL
• C. 2.6 mL
• D. 3.0 mL

Answer: (B)

Blood collection from a rat is limited by its circulating blood volume to prevent hypovolemia and harm. The common guideline is to take no more than about 1% of the animal’s body weight in a single draw. For a typical lab rat around 130 g, that corresponds to roughly 1.3 mL. The other options are either too small to be a practical single draw or exceed the safe single-draw limit (for example, 2.6 mL or 3.0 mL would be too large for a typical session). If more blood is needed, samples should be collected in smaller increments over time or from additional animals.