ICD-10-CM Underdosing Guidelines and Accuracy

Gloryanne Bryant, RHIA, CDIP, CCS, CCDS Medical Coding Leave a Comment

ICD-10-CM Underdosing Guidelines and Accuracy

The clinical coding of “Underdosing” has some very specific guidelines which must be understood and followed. We see “underdosing” scenario’s occur in both outpatient and inpatient encounters. Several ICD-10-CM codes will need to be assigned in order to capture the underdosing patient encounter accurately. 

The clinical coding of a condition or diagnosis of “Underdosing” takes knowledge, understanding, attention to documentation and guideline details. In the Merriam Webster online dictionary, we find this meaning of “underdosing”: 

  • to take or administer an insufficient dose  
  • noncompliant patients may tend to underdose 

Within the ICD-10-CM Official Guidelines for Coding and Reporting we find that “Underdosing” is mentioned 20 times. The Official Guidelines for the coding of “underdosing” is found in 1.C.19.e.5.c   

The coding Conventions of ICD-10-CM tell us there is a “Placeholder character” needed with some codes. In  ICD-10-CM we utilize a placeholder character of “X”, which is used as a placeholder with certain codes to allow for future expansion. An example of this is at the poisoning, adverse effect and underdosing codes, categories T36-T50. Where a placeholder exists, the X must be used in order for the code to be considered a valid code. 

Per the Official Guidelines: 

  • Underdosing refers to taking less of a medication than is prescribed by a provider or a manufacturer’s instruction.  
  • Discontinuing the use of a prescribed medication on the patient’s own initiative (not directed by the patient's provider) is also classified as an underdosing. For underdosing, assign the code from categories T36-T50 (fifth or sixth character “6”). 
  • Codes for underdosing should never be assigned as principal or first-listed codes. If a patient has a relapse or exacerbation of the medical condition for which the drug is prescribed because of the reduction in dose, then the medical condition itself should be coded. 
  • Noncompliance (Z91.12-, Z91.13- and Z91.14-) or complication of care (Y63.6-Y63.9) codes are to be used with an underdosing code to indicate intent, if known.  

The Official Guidelines are available (for free) at: FY2022 April1 update ICD-10-CM Guidelines (cms.gov) 

AHA Coding Clinic recently provided additional guidance regarding underdosing. When the patient discontinues his/her medication and there is no change in their condition, the guidelines do not preclude the coding professional from assigning the underdosing codes. Ultimately, there may also be documentation as to “why” the patient discontinued or stopped their medication, i.e., Low Income Z59.6, so adding a code from or for Social Determinants of Health may be added as a secondary code. 

In order to obtain accuracy with the coding of underdosing, we may find several ICD-10-CM codes need to be assigned to fully capture all the required information. 

  • Underdosing code from T36-T50 range 
  • Sign/Symptom or medical condition code (from not taking a medication) 
  • Non-Compliance code  
  • Complication of care code 
  • Social Determinants of Health code 

Remember, when a clinical scenario presents in the medical record documentation that is unclear, incomplete, conflicting or contrasting you should query the provider for clarification. 

Also, note that the 2023 Medicare Advantage final rule stated that the Centers for Medicare and Medicaid Services (CMS) has been testing the Pharmacy Quality Alliance (PQA) socioeconomic status (SES) or sociodemographic status (SDS) specifications with the following PQA recommendations, one of which is:  

  • Medication adherence for diabetes, hypertension, and cholesterol should be risk-adjusted for SDS characteristics to account for population differences. 

As you can tell, there are lots to consider when coding an underdosing scenario. Capturing compliance with medication adherence can give a true picture of the patient's situation and explain the treatment and services that the patient receives. Thus, the next step to take is to plan and conduct a focused coding audit on “underdosing” accuracy in both outpatient and inpatient settings and confirm all secondary (additional) codes are assigned. 

MRA is available to provide consulting assistance and resources for auditing and education.

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