Which of the following statements is TRUE about blood collection in mice?

• A. Sedation causes vasoconstriction which makes the tail vein harder to locate
• B. Sedation has no effect on tail vein visibility
• C. Sedation is contraindicated for tail vein collection
• D. Sedation causes vasodilation which helps make the tail vein easier to find

Answer: (D)

When drawing blood from a mouse’s tail, making the vein easy to see and access is the main goal. Sedation often causes vasodilation, which expands peripheral veins like the tail vein. That widening makes the vein more visible under the skin and easier to cannulate or puncture with a needle. At the same time, sedation reduces movement and stress, which helps you target the vein more precisely. If veins vasoconstricted, they’d shrink and become harder to locate, so the idea that sedation helps by widening the vein fits why the statement is true.