Breaking Down the E/M Prolonged Service Guidelines 99358 and 99359 into Digestible Nuggets with Scenario Examples (Pt. 2 of 3)

by Mrs. Jay, Curriculum Director of Absolute Medical Coding Institute. 

Mastering Prolonged Services Coding: A Guide to 99358 and 99359

Evaluation and Management (E/M) prolonged services codes 99358 and 99359 are essential tools for healthcare providers to accurately capture and bill for the additional time spent on patient care beyond the standard E/M service for physicians and Qualified Healthcare Professionals (QHP). In this blog post, we will explore the specifics of these codes, their appropriate usage, and tips for successful documentation.

Understanding Prolonged Services Codes 99358 and 99359

99358 and 99359 are prolonged service codes used with a primary face-to-face E/M service code to account for extended time spent on a patient’s care on a day different than the primary face-to-face service but related to a primary face-to-face service. 

99358: Prolonged evaluation and management service before and/or after direct patient care; first hour 

99359: Each additional 30 minutes (List separately in addition to code for prolonged service)

It is essential to remember that 99358 is a standalone code that must be billed in relation to a direct/face-to-face encounter, and 99359 is an add-on code that must always be billed in conjunction with 99358. 

When to Use Prolonged Services Codes 99358 and 99359

Prolonged service codes should be used when a healthcare provider spends significantly beyond the usual service time for a specific E/M code. The additional time must be:  

Key Guidelines pertinent to 99358 and 99359

  • Note that prolonged services codes apply only to non-face-to-face services, such as reviewing records, communicating with other healthcare professionals, or counseling the patient’s family. The Prolonged service must be on a different day (before or after) than a related face-to-face encounter. 
  • The related face-to-face encounter does not have the required time specifications.
  • Prolonged services of less than 30 minutes are not coded.
  • Use 99358 when at least 30 minutes beyond the typical time is met (30 – 74 minutes) 
  • Use 99359 for each additional 30 minutes of prolonged time. For the final units of prolonged time, a minimum of 15 minutes must be met to use code 99359
  • The services rendered must be medically necessary and directly related to any face-to-face E/M encounter.
  • 99358 may only be used once per date of service
  • 99359 may be used on any given date of service with 99358
  • Time is not required for the related face-to-face/direct E/M service.
  • Codes 99358 and 99359 are to be used by physicians/QHPs

Proper Documentation for Prolonged Services

Thorough documentation is crucial when billing for prolonged services to ensure accurate reimbursement and avoid potential audits. Key elements to include in your documentation are:

  • The start and end times of the prolonged service
  • A detailed explanation of the additional services provided during the prolonged period
  • A clear description of the medical necessity for the prolonged service
  • Reference the primary face-to-face E/M service code with which the prolonged services are related
  • Clearly differentiate the prolonged service time from the time spent on the primary E/M service
  • Ensure the total time spent on the prolonged service is accurately documented, including start and end times

Application to Practice:

Scenario for 99358:

Dr. Khan spent 45 minutes reviewing extensive medical records, laboratory results, and imaging studies for her patient, Mrs. Martinez, who has a complex medical history, before their scheduled office visit. This additional time was necessary to develop a comprehensive treatment plan tailored to Mrs. Jones’s needs. Code for the encounter? 


In this scenario, the physician is spending prolonged time before a related encounter (note this encounter is not on the same day as the face-to-face encounter, which is documented as upcoming.) Also, the upcoming face-to-face encounter is not documented and thus has no time specifications or requirements. We are directed to code 99358 for the first hour of a prolonged time. However, when the time is less than one hour (as in our case), we can use code 99358 as long as a minimum of 30 minutes has been met. 

See the chart below.

Final Answer: 99358 

Scenario for 99358 and 99359:

Dr. Wang spent one hour and 45 minutes reviewing detailed medical records, consulting with other healthcare professionals, and coordinating a multidisciplinary care plan for Mr. Thompson, a patient with multiple chronic conditions, the following day after an office visit with Mr. Stein. Code for the encounter: ___________________________


In the scenario, Dr. Wang spent one hour and 45 minutes of prolonged time on a date other than a RELATED face-to-face encounter. The face-to-face encounter occurred on the day prior, so this is an eligible prolonged physician encounter. If we convert one hour of time to minutes, we have 105 minutes. If you look at the chart below the codes, you are directed to code 99358, 99359×2. The first 60 minutes were coded with 99358, The next 30 minutes with 99359, then the final 15 minutes with 99359. 

Final Answer: 99358, 99539×2


Prolonged services codes 99358 and 99359 are vital for healthcare providers to accurately bill for the extra time spent on patient care beyond the standard E/M services. By understanding the appropriate usage of these codes, maintaining thorough documentation, and following best practices for billing, healthcare providers can ensure they receive fair compensation for their extended efforts in patient care.