How many times should most tubes be gently inverted after filling?

• A. 1 to 2 times.
• B. 3 to 4 times.
• C. 5 to 8 times.
• D. 9 to 12 times.

Answer: (C)

Mixing the blood with the additive by gentle inversion distributes the additive evenly and helps prevent clot formation, ensuring accurate test results. For most tubes, gently inverting about five to eight times after filling provides enough mixing without causing damage or foaming. This range effectively distributes common additives like anticoagulants while keeping cells intact. Some tubes, such as those containing citrate, require fewer inversions (about three to four) to maintain the correct blood-to-anticoagulant ratio, but five to eight times is the best general guideline for most tubes.