8. Test values can be different from lab to lab
Lab technicians’ reports compare your blood test results to a range that is considered normal for that laboratory. The lab’s reference range is based on test results from many people previously tested in that lab. This normal range may not be the same as another lab’s, notes the U.S. Food and Drug Administration, so don’t be surprised if you find that a prior blood test report varies from newer reports — the difference could be in the lab.
9. Abnormal results might not be due to a disease
A test result outside the normal range of expected lab values could lead to diagnosis of a disease or disorder. But test outcomes can also be abnormal for other reasons. If you had a blood glucose test and you ate something before the test, or were drinking alcohol the night before or taking certain medications, your result could be temporarily abnormal.
10. Mistakes happen
Although mix-ups of patient blood test samples are rare, they do happen, like in the case of an HIV patient’s sample that was switched with another person’s, accidentally, as reported on ABC News. How your blood sample is handled even before it’s analyzed can affect results, too. For example, if the technician shakes your blood sample in the collection tube, blood cells break open, releasing their contents and potentially changing the test results.