90791 CPT Code: Psychiatric Diagnostic Evaluation

What 90791 Covers

CPT code 90791 covers a psychiatric diagnostic interview to evaluate a patient’s presenting concerns, psychiatric history, functional status, and current mental status. This evaluation is detailed enough to establish a clear diagnosis and develop a well-informed written treatment plan.

While the AMA does not mandate a minimum session length for 90791, most payers expect documentation that reflects 45 to 60 minutes. Importantly, this code is strictly limited to psychiatric diagnostic evaluation and excludes medical services such as prescribing medications, adjusting dosages, performing physical examinations, or ordering laboratory studies. Those elements are captured under code 90792.

When to Use 90791

Use 90791 for the initial intake evaluation performed by a therapist, psychologist, licensed clinical social worker, or a qualified non-prescribing mental health provider.

Here’s how it compares to other common codes:

• 90791 vs. 90792: Choose 90792 when a psychiatrist or other prescribing provider conducts the diagnostic evaluation and medical services are part of the encounter. If no medical services are involved, 90791 is the appropriate code.

• 90791 vs. 90837: 90837 is for ongoing individual psychotherapy, not for the initial evaluation. Once a diagnosis and treatment plan are established, switch to the appropriate psychotherapy code for follow-up sessions. 90791 should not be used as a recurring therapy code.

• 90791 + Same-Day Psychotherapy: Some payers allow billing 90791 together with a psychotherapy code on the same date when the evaluation and therapy are distinct services. However, most require a modifier or prohibit the combination entirely. 

Documentation that Keeps 90791 Paid

90791 is a high-value code that is keenly scrutinized by payers, especially when billed more than once per episode of care or on the same date as therapy. 

For faster approvals, begin with a comprehensive document that captures the full clinical picture:

• Medical history: Document presenting problem, psychiatric history, prior treatment and hospitalizations.

• Mental status examination: Include a structured MSE covering appearance, behavior, speech, mood and affect, thought process and judgment of the patient. 

• Diagnosis and clinical formulation: Assign DSM-5 or ICD-10 diagnoses with supporting rationale to pass payer review. 

• Treatment plan: Evaluations should include modality, frequency, goals, and any referrals or care coordination to justify the service level.

Common Denial and Audit Triggers

• Thin documentation: Missing MSE, history, or treatment plan elements trigger downcoding.

• 90791 vs. 90792 mismatch: Prescribing provider bills 90791 instead of 90792 when medication was discussed or initiated during the evaluation.

• Same-day psychotherapy conflict: 90791 and 90837 billed on the same date without a modifier where required, or billed to a payer that prohibits same-day pairing entirely.

• Credential issues: 90791 billed under a supervisor’s NPI when the rendering provider is not credentialed. 

Telehealth Billing

90791 is covered via telehealth by Medicare and most commercial payers. Use modifier 95 for real-time audio-video evaluations and modifier 93 for audio-only delivery where covered. POS 02 applies when the patient is not at home, whereas POS 10 applies to home-based telehealth. 

How 90791 Pairs with Other Codes

90791 is a standalone code for psychiatric diagnostic evaluations and intake sessions. It’s not billable on the same day as psychotherapy codes (90832–90837) when performed by the same provider. However, it can be reported alongside separate E/M services on the same day by different providers, or with modifier 25 when the services are clinically distinct, appropriately documented, and medically necessary. 

Frequently Asked Questions

What is the difference between 90791 and 90792?

90791 is a psychiatric diagnostic evaluation without medical services, used by non-prescribing providers or by prescribers when no medication management occurs during the encounter. 90792, on the other hand, includes medical services and is appropriate when a psychiatrist or other prescribing clinician evaluates the patient and addresses medication during the same encounter. 

Does 90791 require prior authorization?

Many commercial payers and Medicaid managed care plans require prior authorization for psychiatric evaluations. 

Does 90791 have a minimum time requirement?

No. 90791 is not time-based under AMA guidelines. There is no specific time threshold, but the service must be comprehensive enough to support a diagnosis and treatment plan.