Your Patient’s Lab Is Abnormal. Now What?
Learning normal lab ranges is an important part of nursing school. You learn that a low hemoglobin may indicate anemia or blood loss. You learn that creatinine can give you information about kidney function. You memorize normal ranges for sodium, platelets, glucose, magnesium, and dozens of other values.
But eventually, knowing the normal range isn't enough. Because nursing questions (and real patients) don't usually ask: Is this lab value high or low?
They ask you to figure out what that result means for the patient and what you should do with that information. When a lab comes back abnormal, don't stop at the H or L next to the result. Here's what to look at next.
Look at the Actual Result
When a lab result is outside the expected range, look at the actual value, not just the H or L beside it. For example:
Potassium: 3.4 mEq/L
Potassium: 2.4 mEq/L
Both results are below the expected range, but the second value carries a much greater risk for complications. This doesn't mean the number furthest from normal should automatically become your priority. It means you need to consider the actual value along with the rest of the clinical picture.
A slightly abnormal result in a stable patient may require monitoring. A more significant change, especially when it is accompanied by concerning symptoms, assessment findings, or changes in vital signs, may require more immediate attention.
So when you see an H or L on a lab report, don't stop there. Look at the value. Then look at the patient.
Connect the Lab to Your Assessment
An abnormal lab result should be considered along with what you're seeing in the patient. For example, your patient's platelet count is 52,000/mm³.
You know the platelet count is low. But your assessment gives you additional information. The patient has new petechiae, bruising, and bleeding around the IV site.
Now the lab result has clinical context. The low platelet count isn't just something you noticed on the lab report, the patient is also showing signs of increased bleeding.
This is why your assessment matters when interpreting lab results. Ask yourself: Does this lab result help explain what I'm seeing in my patient?
Look at the Trend
Don't look at the most recent lab result by itself. Compare it with the patient's previous results.
For example, a 77-year-old patient admitted with pneumonia has a hemoglobin of 11.2 g/dL. The value is below the expected range, but when you review the patient's recent results, you see:
11.1 → 11.3 → 11.2 g/dL
The hemoglobin is low, but it has remained relatively stable. Now consider a postoperative patient whose hemoglobin has changed from:
Yesterday: 13.2 g/dL
This morning: 11.2 g/dL
Six hours later: 9.4 g/dL
The current hemoglobin is important, but so is the fact that it has continued to decrease over a short period of time. Now consider the patient's assessment findings:
HR: 118/min
BP: 92/58 mmHg
Reports dizziness
Increasing bloody drainage from the surgical site
Together, the decreasing hemoglobin and the patient's assessment findings raise concern for ongoing blood loss and changes in perfusion. This is why previous lab results matter. They help you determine whether an abnormal value is stable, improving, or getting worse.
Look for a Reason
When a lab result is abnormal, consider what is happening with the patient that could be contributing to it. Look at the patient's diagnosis, medications, treatments, recent procedures, intake and output, and recent changes in condition.
For example, a patient's creatinine has increased from 0.9 to 1.8 mg/dL. The patient has also had vomiting and diarrhea for several days, poor oral intake, and decreasing urine output. Those additional findings provide important context. Fluid loss and poor intake may contribute to decreased renal perfusion and help explain the rising creatinine.
Now you're doing more than recognizing an elevated creatinine. You're connecting the lab result to what has been happening with the patient.
Look at Related Lab Results
One abnormal lab result may lead you to look at other related results for more information.
For example, if a patient's hemoglobin has decreased, look at the hematocrit as well. If the creatinine is elevated, reviewing the BUN and electrolytes may provide additional information about the patient's renal function and fluid status.
The same applies when several abnormal results appear together. A low platelet count may be more concerning when the patient also has abnormal coagulation results or signs of bleeding.
Does the Lab Change What You Do Next?
Lab results can affect medications, treatments, and other nursing interventions. Before carrying out an order, make sure the patient's most recent results still support what you're about to do.
For example, your patient has an order for: Potassium chloride 40 mEq PO. Before administering the medication, you review the morning labs and see Potassium: 5.8 mEq/L.
The potassium is already elevated. Giving additional potassium could raise the level further, so the nurse should hold the medication and clarify the order with the provider according to facility policy.
This is why reviewing lab results isn't just about identifying what is high or low. Sometimes a new result means you need to change what you were about to do.
Depending on the situation, an abnormal lab result may mean you need to:
Reassess the patient
Hold or question a medication or treatment
Gather additional information
Take an appropriate nursing action
Notify the provider or escalate a concern
Before moving forward, ask: Does this lab result affect what I should do next?
When You Study Labs, Go One Step Further
Memorizing normal ranges gives you a starting point. But don't let your studying stop there. When you learn a lab, also learn: What makes it increase or decrease? What might I see in the patient when it's significantly abnormal? When can it become dangerous? Which medications can affect it? Which medications or treatments could become unsafe because of it? What might the nurse need to assess, monitor, hold, report, or do next?
That's the information that helps you move from memorizing a lab value to using it in a patient scenario. Knowing the normal range helps you recognize that something is abnormal. Clinical judgment is figuring out why that abnormality matters and what should happen next.
Don't Just Learn the Lab. Learn What to Do With It.
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