CPT Code 99231: Subsequent Hospital Care, Low Complexity

CPT code 99231 covers subsequent hospital inpatient or observation care with low-complexity medical decision making. Learn when to use it, documentation needs, and billing guidelines.

Use Code

What is CPT code 9923?

99231 CPT code is used to report subsequent hospital inpatient or observation care services involving low-complexity medical decision making (MDM). It typically reflects a follow-up visit during a patient’s stay, where the provider reviews progress, adjusts treatment, or monitors response to therapy. This service does not involve the intensity or complexity required for initial admission or discharge codes.

This code is part of a family of hospital care CPT codes (99231–99233) used after the initial admission. It may apply to inpatients or patients under observation care services if the care is non-emergent and ongoing.

Documentation requirements

To support CPT 99231, providers must document a medically appropriate history and/or examination and low-level medical decision-making. The visit note should reflect straightforward issues that require minimal data review and pose a low risk of complications or morbidity. Typical documentation includes review of patient status, medication changes, brief updates to care plans, and follow-up on routine labs or vitals.

The medical necessity for continued care must be clear. Even if the visit is brief, the note should demonstrate why physician input was needed that day, particularly about the patient’s hospital course or observation status.

Billing guidelines

Correctly billing CPT code 99231 requires a clear understanding of the service type, patient status, and the complexity of medical decision making.

When to use CPT 99231

Use CPT 99231 when evaluating a hospital inpatient or observation patient whose medical decision-making is considered low complexity. This often includes stable, recovering patients who require minimal monitoring or routine adjustments. The code may also be appropriate for patients with minor issues that do not require extended data review or intervention.

Exclusions and common errors

Do not use CPT 99231 for initial hospital admissions—use codes 99221–99223 for that purpose. Also, avoid using this code for discharge day management (e.g., 99238 or 99239), emergency department services, or observation discharge services (e.g., 99217). Ensure the level of medical decision-making aligns with what is documented, and avoid upcoding if the complexity is minimal.

Time component

While time is not the primary driver of hospital visit codes as of the 2023 E/M update, if time is used to select the code, CPT 99231 typically reflects at least 25 minutes of total time spent on the service date. Time may include activities like chart review, patient communication, and documentation, as long as they occur on the same calendar day.

Other relevant CPT codes

99221–99223: Initial hospital inpatient or observation care
99232, 99233: Subsequent hospital care with moderate or high complexity medical decision making
99217: Observation discharge day management

Frequently asked questions

CPT 99231 includes a medically appropriate history and/or physical exam and low-complexity medical decision-making (MDM). It is typically used for subsequent hospital or observation visits, where the provider evaluates the patient’s progress, adjusts treatment as needed, and addresses routine inpatient issues.

Yes, CPT 99231 applies to both hospital inpatient and observation care services. It is used after the initial admission to document follow-up care during a patient’s stay.

CPT 99231 is used for subsequent hospital care, not initial admission and discharge services (99221–99223; 99238–99239). It documents ongoing daily care, not the start or end of a hospital stay. It's also not used for emergency department visits.