MDM vs Time in Outpatient Psychiatry — Which Should You Use?

Since the 2021 E/M guideline changes, psychiatric prescribers can select their outpatient visit level using either medical decision making or total time. Most clinicians default to one method out of habit. The better approach is understanding which method more accurately reflects what actually happened in the visit — and using that one.

The Basic Rule

Time measures presence. MDM measures judgment. You use whichever one more accurately reflects the work you performed.

For visits without a psychotherapy add-on, you choose either method. For visits where you bill a psychotherapy add-on code (90833, 90836, 90838), the E/M level must be selected using MDM. Time cannot be used to select the E/M level when psychotherapy is also billed.

When Time-Based Billing Makes More Sense

Use time when the visit was long because the patient needed your time and attention — not because the clinical decisions were complex.

A stable patient who needed 35 minutes of reassurance, education, and support around life stressors is a time-based visit. No complex medication decisions were made. No diagnostic uncertainty existed. The visit was long because the patient needed the time, not because you needed advanced clinical reasoning.

Under CPT time guidelines, total time includes face-to-face time plus non-face-to-face time you personally spent on the date of the encounter — reviewing records before the visit, documenting after, care coordination, ordering. It all counts.

When MDM-Based Billing Makes More Sense

Use MDM when the visit required clinical judgment regardless of how long it took.

A 22-minute visit where you reviewed records from two prior psychiatrists, clarified a diagnostic question, and initiated a new medication after careful risk assessment is a moderate complexity MDM visit. By time, 22 minutes only supports 99213. By MDM, the clinical work supports 99214. If you bill by time here, you underbill.

MDM captures complexity that time misses. Short does not mean simple.

The Mixed Visit Rule

When you bill E/M with a psychotherapy add-on, the rules change completely. The E/M level must be selected based on MDM. Time cannot be used. Psychotherapy minutes are reported separately and cannot be counted toward the E/M.

This is not a payer-specific interpretation. It is CPT guidance, stated explicitly in the 2025 CPT manual: "Time may not be used as the basis of E/M code selection and prolonged services may not be reported when psychotherapy with E/M (90833, 90836, 90838) are reported."

New Patient Evaluations — Where Time Often Wins

For new patient evaluations, time frequently supports a higher code level than MDM alone would. A straightforward new patient with a single clear diagnosis may only meet MDM criteria for 99204. But gathering a complete psychiatric history, reviewing prior records, completing the mental status exam, discussing diagnosis and treatment options, and documenting the encounter will often push total time past 60 minutes — supporting 99205 by time, and potentially prolonged service codes beyond that threshold.

This is one of the clearest examples in outpatient psychiatry where time-based billing is not just acceptable but more accurate. You did not do high-complexity MDM work, but you absolutely spent the time. Bill for what actually happened.

The Practical Decision

Before you choose your method, ask: Was this visit long because the patient needed time, or complex because the clinical situation required judgment? If time, bill by time. If judgment, bill by MDM. If both point to the same code, document the cleaner method and move on.

The complete decision framework — including case examples, psychotherapy add-on rules, and common coding errors — is covered in Billing I: Choosing Time vs MDM inside Think Beyond Education.