How to Write a Nursing Diagnosis

You write a nursing diagnosis in PES format — Problem (the patient's response), Etiology (the cause, introduced by "related to"), and Signs/symptoms (the evidence, introduced by "as evidenced by") — after clustering and analyzing your assessment data. The result reads as a single sentence that traces straight back to what you actually found on the patient.

Every well-formed nursing diagnosis answers three questions in order: what is the patient's problem, why is it happening, and how do you know? PES format just gives those three answers a consistent shape so any nurse reading it can follow your reasoning without asking you to explain it out loud.

Step 1: Cluster your assessment data

Before you can name a problem, you need to see the pattern in your data. Go through your assessment — vital signs, lab values, what the patient told you, what you observed — and group the findings that seem to point at the same issue. A patient with a productive cough, crackles on auscultation, and an oxygen saturation of 91% isn't three separate findings; it's one cluster pointing at a breathing problem. Clustering first keeps you from jumping to a diagnosis based on a single data point.

Step 2: Identify the problem (the human response)

Once the data is clustered, name the patient's response to what's happening — not the medical condition itself. The medical diagnosis is what the physician named (pneumonia, a hip fracture, heart failure); the nursing diagnosis is how this specific patient is responding to it (impaired gas exchange, impaired physical mobility, decreased activity tolerance). Two patients with the same medical diagnosis can have completely different nursing diagnoses, because their responses differ.

Step 3: Determine the etiology ("related to")

The etiology is the factor driving the problem — the piece your interventions are actually aimed at changing. Look back at the cluster: what's the mechanism connecting the data to the problem? For the breathing example above, the etiology might be excess airway secretions. Notice this is not "pneumonia" — a medical diagnosis can't be the etiology, because nursing interventions can't cure pneumonia. They can, however, help clear secretions, which is why the etiology has to be something a nurse can act on.

Step 4: Attach the evidence ("as evidenced by")

The evidence section is where you prove the problem is real by citing the specific, measurable signs and symptoms from your assessment — not a general impression. "Patient seems short of breath" is not evidence; "oxygen saturation 91% on room air, respiratory rate 26, scattered crackles bilateral bases" is evidence. Anyone reading the diagnosis should be able to picture exactly what you saw, heard, or measured.

Step 5: Building the full example

Here's the same patient built up one piece at a time:

1. Data cluster: Productive cough, scattered crackles bilateral bases, oxygen saturation 91% on room air, respiratory rate 26/min, patient reports "it's hard to get a full breath."
2. Problem: Impaired gas exchange.
3. Etiology: Related to excess airway secretions.
4. Evidence: As evidenced by oxygen saturation of 91% on room air, respiratory rate of 26/min, and bilateral crackles on auscultation.
5. Full statement: Impaired gas exchange related to excess airway secretions as evidenced by oxygen saturation of 91% on room air, respiratory rate of 26/min, and bilateral crackles on auscultation.

The PES parts at a glance

How a risk diagnosis is different

A risk diagnosis describes a problem the patient doesn't have yet but is vulnerable to, so the format drops a whole clause. There's no current evidence to cite — because the problem hasn't happened, there's nothing to observe or measure — so a risk diagnosis has no "as evidenced by" section at all. It uses only "related to," followed by the risk factors that make the patient vulnerable. For a bedridden patient with intact skin, that might read: risk for impaired skin integrity related to immobility and prolonged pressure on bony prominences. That's the complete statement; there's no signs-and-symptoms clause tacked on, since by definition the problem hasn't shown up yet.

Common mistakes that cost points

• Using a medical diagnosis as the problem. "Pneumonia" is not a nursing diagnosis — it's what the physician named. Ask what the patient's response to pneumonia actually is (impaired gas exchange, activity intolerance, anxiety) and use that instead.
• Writing "related to" a medical diagnosis. Even if the problem is worded correctly, an etiology like "related to pneumonia" is still a medical condition your nursing care can't directly change. Push one level deeper to the mechanism — thick secretions, decreased lung expansion, fatigue — something an intervention can target.
• Citing unmeasurable "evidence." Vague phrases like "patient appears uncomfortable" or "seems anxious" aren't evidence because they can't be verified by another nurse. Replace them with specific, observable data: a pain scale number, a vital sign, a quote from the patient, a wound measurement.

Once you're comfortable writing the diagnosis itself, the next step is fitting it into the rest of the document: see how to write a nursing care plan for the full five-part structure, browse types of nursing diagnosis to double-check which category fits your patient, or look at nursing diagnosis examples for more filled-in PES statements across common conditions.