I am a 23 year nurse and I do remember the frustration. Instructor would say, "Why is this test ordered? What does it tell you? What should be your response?"
Text books and lab manuals only seemed partially helpful, I thought.
And let's not even talk about ABG's!!!
The only thing I can tell you is that, in time, this gets easier. But like so much of nursing, you just have to get in and start swimming. This is where noticing what tests the doc orders, what he says about them in the progress notes and how the staff nurses respond to them can help you over time.
Broadly, labs can be ordered to diagnosis or to monitor or to screen. See if you can discern which reason the test is being ordered. Examples of each. A young woman who claims she is not sexually active comes in for surgery, and they do a pregnancy test. This is a screening test. A young woman comes in wanting to be pregnant and has not had a period for two months. They do a pregnancy test. This is diagnostic. A young woman comes in with history of a positive qualitative pregnancy test. She is early in her pregnancy (like 6 weeks) and spotting. The doctor may order serial quantatative pregnancy tests. This is monitoring.
Confusing, because we were talking about pregnancy tests all 3 times. The first two tests are likely the same technology (urine), the latter is going to be different technology (serum). We are looking for slightly different types of information for slightly different types of reasons.
The reason that I drag you through this confusing knot hole is to make this point. _The test's importance is determined by the context_.
If the routine surgery patient's test is POSITIVE, it is a stop the presses moment and the anesthesia and surgery staff need that information, preferably before they put her to sleep.
If the woman who wants to be pregnant is pregnant, she's happy. IF not, she's sad. If she's diabetic, the "news" should launch a plan to promptly get her in care.
The spotting patient's serial tests will tell you whether she's experiencing SAB and generate a plan of care for what comes next.
Learning how lab fits into the context of care is a process. Use all the cues you can from experienced practitioners and just realize their is a learning curve.