Diagnostic Evaluation: Using CPT Code 90791
CPT codes create a common language across behavioral health billing, clinical documentation, and payer communication. Each code represents a specific type of clinical service, making it possible for anyone in healthcare to understand the care that was provided.
CPT Code 90791 refers to a comprehensive psychiatric diagnostic evaluation. That includes gathering a detailed history, assessing symptoms, identifying risk, forming diagnostic impressions, and determining what happens next in treatment.
Behavioral health practices use this evaluation to establish medical necessity and guide care decisions. Payers scrutinize 90791 documentation during reviews, so practices need to understand when the code should be used, how to document the evaluation, and what distinguishes it from other services.
What is CPT Code 90791?
CPT Code 90791 is not a catch-all. It’s a specific, structured encounter where a clinician collects information from multiple sources, including patient interviews, past records, and screening or assessment tools. The goal is to understand the patient’s current symptoms, functional impairments, history, risk factors, and treatment needs. This evaluation becomes the foundation for a treatment plan.
The code description specifies a psychiatric diagnostic evaluation without medical services. This means the evaluation focuses on clinical assessment and diagnosis only, without including medication management or other any other medical interventions. Because authorization requests for ongoing services are often based on this type of evaluation, incomplete or poor documentation can result in denials or delays.
When to Use 90791
Clinicians often use 90791 during the first appointment with a new patient. It can also be billed when an existing patient experiences a significant change that warrants a full reassessment—a crisis event, a change in diagnosis, or a transition into a higher level of care.
90791 is focused on evaluation rather than ongoing treatment. This means payers expect documentation to reflect a diagnostic process, not therapeutic work, when this code is billed.
Common scenarios for billing 90791 include:
- Initial intake evaluations for new patients entering outpatient therapy
- Assessments before admission to intensive outpatient or partial hospitalization programs
- Comprehensive reassessments when a patient’s diagnosis or treatment plan requires significant revision
- Evaluations following psychiatric hospitalization to determine appropriate outpatient care
- Diagnostic clarification when previous treatment hasn’t been effective
The code should not be used for follow-up appointments that do not involve comprehensive diagnostic assessment.
Documentation and Billing Requirements
When using 90791, accurate documentation is essential. Evaluations should demonstrate that all relevant bases have been covered, including the patient’s primary complaint and presenting concerns; psychiatric history; medical history related to mental health treatment, such as chronic conditions; substance use history; trauma history if relevant to current symptoms; social history; developmental history if relevant; and current medications.
The evaluation should also document factors such as behavior, speech, mood, and judgment. A structured assessment provides observations that can support diagnostic impressions.
Risk assessment is another important component. Clinicians must document any suicidal ideation as well as related factors; history of suicide attempts or self-harm; history of violence or aggressive behavior; and overall assessment of risk level. Corresponding safety planning is crucial. Payers review risk documentation to make sure treatment recommendations align with the patient’s safety needs.
Functional assessment should describe how symptoms affect daily life. This includes ability to maintain employment or attend school, capacity to manage self-care and daily living activities, quality of relationships, and other areas where symptoms impact the patient’s life. Functional impairment is often a key indicator for medical necessity, so documentation should clearly connect symptoms to their real-world effects.
Diagnostic impressions should be supported by the information gathered during the evaluation. Rather than just noting “Major Depressive Disorder,” the clinician might explain that the diagnosis is based on persistent low mood for three months, sleep disturbance, difficulty concentrating, and significant impact on work performance.
The treatment plan should outline recommended interventions, intended frequency and duration of services, and specific goals for treatment. It should make clear how the proposed services address the patient’s needs.
Common Errors and Best Practices
Insufficient detail, missing risk assessments, or unclear diagnostic justification can result in denials or payer requests for additional information, adding to a practice’s administrative load. Practices with multiple providers may even have variability in documentation quality.
An internal review process to monitor documentation and provide feedback can prevent repeat issues and help with compliance. Standardized templates help ensure that each evaluation includes the required elements.
Common errors in 90791 claims include using it for brief or medication-focused visits, documenting therapy instead of evaluation, or omitting things that payers expect in a diagnostic evaluation. Because payers typically don’t allow 90791 to be billed with psychotherapy codes on the same date of service, combining evaluation and therapy in a single session and billing for both will not work. And payers reviewing claims can only verify clinical work that is documented in the record, so all documentation must be thorough and complete.
Delays in completing evaluations can slow down treatment planning or authorization processes. Completing evaluations efficiently, when the details are still fresh, makes it possible to submit more reliable claims.
There are some recommended best practices to help practices do that:
- Using structured templates that prompt clinicians to address all required elements
- Conducting peer reviews of documentation to ensure consistency
- Providing standardized training to new clinicians on documentation standards and payer expectations
- Scheduling blocks that allow for comprehensive evaluations
An electronic health record (EHR) software designed to accommodate the documentation needs of behavioral health practices can help these best practices fit into real-world workflows.
90791 vs. 90837
Clinicians and billing teams should not confuse 90791 with 90837, a CPT code for a 60-minute therapy session. Both services take similar amounts of time but serve different purposes. A 90837 session involves addressing symptoms and working toward treatment goals. For example, a clinician might actively work with a patient to process emotions, challenge unhelpful thoughts, or address behavioral patterns.
The clinical focus differs significantly between these codes, and session documentation should reflect that. If a clinician tries to combine a full diagnostic evaluation and a full psychotherapy session in the same visit, payers may deny the claim because the services aren’t separately billable on the same date.
EHR templates can help make sure documentation matches the CPT code billed. Evaluation templates might prompt clinicians to complete all required assessment components, while therapy templates focus on progress documentation. This type of structural support helps ensure accurate documentation.
Treating the 90791 evaluation as a real clinical tool creates a strong foundation for everything that follows. A thorough evaluation gives payers what they need to approve services and reduces back-and-forth over missing information.
Practices that get CPT codes right tend to have fewer billing headaches and better patient outcomes. Setting clear documentation standards and building efficient workflows means clinical records are clearer and more useful. A solid diagnostic evaluation benefits everyone—patients, clinicians, and the practice.
