How to read your lab results

I have sat with a portal notification at dinner and tried to decide whether a flagged value was an emergency. It almost never is, on its own. A lab test checks a sample of blood, urine, or other fluid or tissue for certain substances and how much of them is there. Some tests give a yes or no. Many give a number that only means something next to your history, your exam, and your other tests.

The range next to the number

That span is usually labelled a reference range, sometimes “normal values.” It is the spread of results seen in large groups of healthy people, and it can differ by group (children versus adults, for one). Healthy people fall outside it. A result just outside may or may not matter. Your provider reads it against the rest of your file, not in isolation.

Two labs can report the same test with different methods and different units. If you are tracking a value over time, same lab is easier. When you cannot, compare each result to its own range, not to last month’s report from somewhere else.

Positive, negative, inconclusive

Negative or normal: the test did not find what it was looking for. You may still need more tests. Positive or abnormal: it did, and some of those need confirmation before anyone calls it a diagnosis. Inconclusive: not clearly either, which usually means a repeat.

Labs do not give a complete picture. The combination of exam, history, family history, and imaging is what leads to a reading. Seeing a result in the portal is a reason to write down a question for the next conversation, not a verdict.

Questions I take in: which of these values matters for my situation? Is this change from last time meaningful, or normal variation? Do you want to repeat any of these? Same units, same lab as before? Bring the printed or downloaded report so you are both looking at the same numbers.