Final answer:
A large glucometer reading followed by a normal one could be caused by contamination, bad test strips, glucometer errors, hematocrit level variations, or operator error.
Step-by-step explanation:
The question involves understanding why a phlebotomist got an inaccurately high glucometer reading on their first attempt, which then returned to normal on the second. There are several factors that could explain this discrepancy. Pollution of the finger or test strip with a substance that contains glucose or interferes with the test could cause a falsely high reading. Improper calibration of the glucometer or an expired or damaged test strip can also lead to inaccurate results. Additionally, in the context of diabetes, a patient who has recently eaten may show a temporarily high glucose level, which stabilizes after some time due to the action of insulin, but this scenario does not seem to apply here as the second reading was normal. Moreover, changes in hematocrit levels can also affect the glucometer's accuracy. Finally, operator error, such as applying too little or too much blood to the test strip, could result in an inaccurate reading.