The nurse documents nursing diagnoses and enters them into the patient record. The identified patient's nursing diagnosis is either written out with a plan of care or entered into the electronic health record.

In some settings, data-driven computerized decision support systems are in place, allowing for more accurate nursing diagnoses. The database within one of these systems includes diagnostic labels defining characteristics, activities, and indicators for nursing. A nurse enters assessment data, and the computer helps by organizing the data into clusters that enhance the ability to select accurate diagnoses. Once diagnoses are selected, the computer system also directs the nurse to intervention options to select for a patient.

When misusing the diagnostic process, a patient might be "misdiagnosed." Familiar sources of error include the following.

• Premature diagnoses based on an incomplete database. An example is a diagnosis of defensive coping made after the patient verbally attacks one nurse attempting to teach self-care for their wound.
• Erroneous diagnoses resulting from an inaccurate database or a faulty data analysis. For example, a diagnosis of dysfunctional grieving is made for a patient crying after learning that their cancer had returned before anyone had time to evaluate whether the response was appropriate.
• Routine diagnoses result from the nurse's failure to tailor data collection and analysis to the unique needs of the patient: For example, a diagnosis of deficient knowledge is made in a diabetic patient who is frequently hospitalized with diabetes-related complications when they have excellent knowledge of diabetes and related self-care but lacks the motivation to care for themself.
• Errors of omission: Failure to modify diagnoses and to identify new diagnoses as the patient's status changes may also be the problem. Failures in diagnosis lead to failures in nursing care.