Which unit is used to report red blood cell counts in males?

Which unit is used to report red blood cell counts in males?

• A. million per liter
• B. million per microliter
• C. billion per liter
• D. thousand per microliter

Answer: (B)

The key idea is that red blood cell counts are expressed as how many cells are in a small volume of blood, and the standard clinical unit is cells per microliter. For a healthy adult male, the typical range is about 4.7 to 6.1 million RBCs per microliter, which is the same as roughly 4.7 to 6.1 x 10^12 cells per liter. So the unit that matches this magnitude and is commonly used in labs is "million per microliter." Other options place the count in much larger or smaller magnitudes (per liter). For example, million per liter would imply about a million cells per liter, far too low; billion per liter would be about a thousand times smaller than the usual per-microliter value; thousand per microliter corresponds to about a billion per liter, which is also not correct for normal ranges. Thus, million per microliter is the standard unit.

The key idea is that red blood cell counts are expressed as how many cells are in a small volume of blood, and the standard clinical unit is cells per microliter. For a healthy adult male, the typical range is about 4.7 to 6.1 million RBCs per microliter, which is the same as roughly 4.7 to 6.1 x 10^12 cells per liter. So the unit that matches this magnitude and is commonly used in labs is "million per microliter." Other options place the count in much larger or smaller magnitudes (per liter). For example, million per liter would imply about a million cells per liter, far too low; billion per liter would be about a thousand times smaller than the usual per-microliter value; thousand per microliter corresponds to about a billion per liter, which is also not correct for normal ranges. Thus, million per microliter is the standard unit.