It's 3:00 a.m., and the unit is dead silent. Suddenly, the lab summons you to a critical potassium case of 5.8 mEq/L and rising, a life-threatening level for the patient who quietly lies in room 204, fast asleep. You instinctively begin to panic; your inner voice, saying "don't wake the doctor," tells you to wait for now, so what should you do?
Scenes like these play out in every unit, and often every night. Lab manuals always provide a "normal range," but rarely a clear "when to panic" range. The difference between an abnormal result and a sincerely dangerous outcome is often subtle. Professional anxiety may seize control over a clinician's rational thinking, since mistakes are a nurse’s nightmare. Mastering the art of interpreting lab results is about moving beyond memorization and into decisive action.
Discover a clear, 3-step critical thinking process as your guide on how to stop, think, and act. Determining whether a lab value warrants a call at 3 a.m. is essential for both seasoned and new night shift nurses, who may be calling a doctor at night for the first time.
Assess the patient & not the number
One rule that separates the rookie from an expert is knowing that lab values are merely data, and not necessarily correlated with the patient. Before you consider reaching for your cellphone, the first and most crucial step in determining what to do for a critical lab value is to perform a rapid, focused nursing assessment and review the lab results.
Immediate actions before you pick up the phone
Results are contextual. Your quick 60-second assessment is the most important piece of data you’ll have.
- Eyes on the patient: Ask yourself these questions at the bedside: Are they breathing comfortably, or are they displaying signs of struggling respiration? Are they awake, disoriented, or softly asleep? This primary observation dictates your next move.
- Get a full set of vitals: Check the patient’s heart rate, blood pressure, oxygen saturation, and respiratory rate as rapidly as possible. A change in any of these metrics increases the severity of the situation.
- Observe the monitor: For electrolyte concerns, determining when to call about high potassium requires checking the monitor first. A potassium level of 5.8 mEq/L is quite concerning. A K+ level of 5.8 mEq/L, combined with freshly peaking T-waves on the EKG monitor, urgently calls for a STAT rapid response team (RRT) and a physician. A K+ of 5.8 mEq/L on an asymptomatic patient who is resting and drinking fluids may indicate a less immediate, though still urgent, course of action.
Remember, focus must remain on the patient's condition. Your quick one-minute report is arguably the most important piece of data you’ll have. Ultimately, you’re treating the patient and not the lab report.
Is this "new," "known," or just "nonsense"?
You have assessed the patient and reviewed the lab results.
Context is everything. Critical thinking is necessary for accurate charting. Elaborate and rapidly noted charts are a necessity and can eliminate up to 90% of unnecessary calls, especially when managing critical lab values across various nursing scenarios.
To answer the question, “Is this lab value critical enough to call at 3 a.m.?” you must contextualize the number within the patient's history and current care plan.
Is it new? Check the trend
Sudden and drastic changes are always more alarming than a gradual drift.
Ask yourself: Is this high potassium level an abrupt occurrence? Or has this patient, perhaps with known renal failure, been trending at levels of 5.5, 5.6, 5.7 for 3 days? Has the physician already been made aware, and are they actively treating it?
Knowing the trend helps you define the level of immediate threat and informs your decision regarding when to call the doctor about lab results.
Is it known? Check the orders
Facilities often have standard protocols in place for common critical values, especially in situations involving high potassium levels.
First, check the current orders and PRN medications. Is there already a standing order for this situation? For example, is there an order in place for "Kayexalate for K>5.5" or a D50 and insulin protocol triggered? If proactive intervention has already been ordered, you may not need to call immediately. Execute the existing order and then notify the physician later.
Is it nonsense? Check the collection
Check for a potential false reading before waking the physician.
Ask yourself: Could the sample collection itself possibly be the problem? Is the lab sample potentially hemolyzed?
Hemolysis is a common cause for a false reading of high K+, artificially elevating the given results. Did you draw the blood from an extremity where a potassium infusion was actively running?
If you strongly suspect a false positive reading, your first action should be to call the lab for an immediate re-draw, rather than contacting your doctor.
Making that 3 a.m. call—while sounding like a pro
Assessments and contextual reviews are now complete; the final step requires decisive action.
Your inalienable checklist
Particular scenarios will demand an immediate phone call. This is when to call the doctor about lab results, even if the patient's current symptoms are subtle.
- Any "critical" value that is new, unexpected, and the patient is symptomatic: A critical value that aligns with patient deterioration (e.g., Hemoglobin (Hgb) 6.5 g/dL combined with new tachycardia and dizziness) is an emergency.
- Any "critical" value for which you do not have an order to treat: If the lab is critical and there is no standing or PRN order for intervention, you must notify the provider.
The "night shift non-negotiables"
Facilities will always have an intricate list of which lab results are critical, since certain values pose such a threat to life that they warrant immediate notification:
- High potassium (K+>5.5 mEq/L): Poses a significant risk of lethal cardiac arrhythmias and cardiac arrest
- Low glucose (BG<60 mg/dL): Risk of hypoglycemia starving the brain and leading to irreversible cell damage and neurological decline
- New positive troponin: Strong indicator of acute myocardial injury or infarction
How to use SBAR: The perfect script
Imagine the doctor answering the phone and the first thing they hear through the line is, "Hi, the lab for room 204 is at 5.8.” Clearly explaining the situation is crucial. Instead of using the vocabulary that first comes to mind, attempt implementing the SBAR speech structure to relay your report while conveying proper urgency and preparation.
SBAR is an abbreviation intended to guide an anxious nurse through the process of how to effectively inform the doctor about a lab’s current status.
- (S)ituation: First, state your name, your location, and the patient you are calling about. For example, "Dr. Smith, this is [Nurse's Name] on 5-West, calling about Mr. Andersen in room 204."
- (B)ackground: Provide a brief and relevant history. "Mr. Andersen is a 62-year-old male diagnosed with chronic kidney disease (CKD). He has been stable and asymptomatic all night."
- (A)ssessment: Now, most importantly, explain the current situation. State your new findings and what you performed. "I just received a new critical lab result of potassium 5.8 mEq/L. I have been to the bedside; he is currently asymptomatic, and his EKG shows a normal sinus rhythm. This is a new high trend for him, and there are no PRN orders to treat it."
- (R)ecommendation: Finally, offer a clear and decisive action that you think would be most appropriate. "Do you want me to give Kayexalate, or would you like me to get a STAT repeat lab first to confirm the result?"
Utilizing the SBAR format demonstrates that you have done your research. You've now given the doctor all the information they need to make a precise decision in under a minute. A good doctor will always respect that level of professional preparation.
Trust your judgment: You’re not bothering anyone
Determining when to call the doctor regarding any given lab results is one of the most significant responsibilities a nurse holds. It is a core skill that defines your clinical expertise, now simpler, clearer, and more actionable than ever:
- Stop and swiftly assess the patient.
- Consider the context of the situation.
- Act by adhering to SBAR, effectively eliminating panic while responding to urgent circumstances with deliberate and data-backed precision.
Fulfilling your professional duty as a nurse is not bothering the doctor.
Never hesitate or apologize for presenting clear data that correlates to a threat to safety. Strong clinical judgment and the confidence to communicate urgent findings effectively are extremely valuable when attempting to understand and communicate lab results. Trust your clinical intuition, but always back it up with well-structured data. You have the skills and the knowledge.
Ready to put your refined skills and confidence to work?Find flexible shifts at facilities that value your expertise today.
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