What is the lowest acceptable hematocrit for allogeneic blood donors?

• A. 36%
• B. 38%
• C. 40%
• D. 42%

Answer: (B)

The main idea is donor safety: ensuring there’s enough red blood cell mass in a donor so that giving blood does not leave them anemic or hypoxic afterward. Hematocrit is the percentage of red blood cells in whole blood, and it serves as a quick measure of that red cell mass. For allogeneic donors, a threshold is set to protect the donor’s health after donation. The lowest acceptable hematocrit is 38%, which means donors must have at least this level to be eligible. Values below 38% indicate insufficient red cell mass and could lead to adverse effects post-donation, so they would be deferred. Values at or above 38% are acceptable, with higher numbers still meeting the requirement but not being the minimum. This threshold roughly corresponds to the commonly used minimum hemoglobin levels, which reinforces the safety rationale behind this cutoff.