The underdosing guideline in ICD-10-CM has been around for years. However, in my auditing and compliance experience, underdosing codes are sometimes assigned incorrectly and are more commonly missed all together. In this blog I will go over the ICD-10-CM Official Guideline regarding underdosing (including the expansion of the guideline for FY2023) as well as examples and Coding Clinic references regarding underdosing.
Underdosing: Official Coding Guidelines
ICD-10-CM Official Guidelines define underdosing as taking less of a medication than is prescribed by a healthcare provider or a manufacturer’s instruction and/or discontinuing the use of a prescribed medication on the patient’s own initiative (not directed by the patient’s healthcare provider).
ICD-10-CM Official Coding Guidelines also provide the following instructions regarding 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
- New for FY2023: Documentation of a change in the patient’s condition is not required in order to assign an underdosing code
- New for FY2023: Documentation that the patient is taking less of a medication than is prescribed or discontinued the prescribed medication is sufficient for code assignment
2023 Guideline Expansion
“Documentation that the patient is taking less of a medication than is prescribed or discontinued the prescribed medication is sufficient for code assignment.”
This means that the healthcare provider does not have to specifically document the term “underdosing.” Documentation that the patient is taking less of a medication than is prescribed or that the patient stopped the medication is sufficient for code assignment. It is also important to note that although the circumstances surrounding the underdosing are helpful for assigning additional codes (e.g., noncompliance codes), the circumstances do not preclude the assignment of underdosing codes.
“Documentation of a change in the patient’s condition is not required in order to assign an underdosing code.”
This means that even if the patient’s condition remained the same when they took less of/discontinued the use of their medication, an underdosing code is still appropriate. This guideline aligns with the advice given in Coding Clinic, First Quarter 2022 Page: 36 “Underdosing with no change in patient’s condition.” The question submitted to Coding Clinic described a patient who stopped taking their prescribed dose of antihypertensive medication several days prior to the encounter but had stable blood pressure. The question asked was whether it would be appropriate to assign a code for underdosing of antihypertensive medication when there was no documentation of an exacerbation or an issue with the patient’s chronic hypertension. The appropriate codes for this example are:
- 5X6A, Underdosing of other antihypertensive drugs, initial encounter
- I10, Essential (primary) hypertension
- 14, Patient’s other noncompliance with medication regimen
Coding Clinic explains that the underdosing code is appropriate, even though there was not a change in the patient’s condition. Documentation that the patient had discontinued the prescribed medication on his/her own is sufficient for code assignment.
Underdosing Examples
Example 1: A patient presents to the ED with hypertensive urgency due to not refilling their Lisinopril. The patient takes Lisinopril for chronic hypertension but was unable to afford the medication this month. The appropriate codes for this example are:
- I16.0, Hypertensive urgency
- I10, Essential (primary) hypertension
- T46.4X6A, Underdosing of angiotensin-converting-enzyme inhibitors, initial encounter
- Z91.1120, Patient’s intentional underdosing of medication regimen due to financial hardship
Both the chronic condition (hypertension) and underdosing exacerbation (hypertensive urgency) are coded in addition to the underdosing code. The noncompliance Z code gives further information regarding the reason for the underdosing.
Example 2: A patient is admitted for aspiration pneumonia. Provider documentation states the patient also has generalized anxiety disorder for which she takes daily Celexa. However, the patient admits to often forgetting to take her Celexa several times over the past month. The provider documents that the patient shows no sign of increased anxiety resulting from the unintentional missed doses of medication and continues treatment during the hospital admission.
- J69.0, Pneumonitis due to inhalation of food and vomit
- F41.1, Generalized anxiety disorder
- T43.226A, Underdosing of selective serotonin reuptake inhibitors, initial encounter
- Z91.138, Patient’s unintentional underdosing of medication regimen for other reason
The reason for admission (aspiration pneumonia) is coded as well as the generalized anxiety disorder. The underdosing code is assigned, even though the underdosing did not exacerbate the patient’s condition. The noncompliance Z code gives further information as to the reason for the underdosing.
Example 3: A type 1 diabetic is seen in the ED due to diabetic ketoacidosis. The patient’s insulin pump malfunctioned and stopped delivering insulin during the night.
- T85.694A, Other mechanical complication of insulin pump, initial encounter
- E10.10, Type 1 diabetes mellitus with ketoacidosis without coma
- T38.3X6A, Underdosing of insulin and oral hypoglycemic [antidiabetic] drugs, initial encounter
The complication code is sequenced first, followed by the diabetic ketoacidosis. The underdosing code is assigned, even though the insulin pump malfunction was of no fault of the patient.
Example 4: A patient is prescribed spironolactone for hormonal acne. However, after consulting with her dermatologist regarding some of her concerns regarding the medication, the dermatologist instructs the patient to discontinue spironolactone and switch to a topical retinoid treatment instead.
- L70.8 Other acne
In this case, no underdosing code is assigned. The patient stopped taking her prescribed medication at the instruction of her doctor.
Full Underdosing Guideline
The underdosing guideline, in its entirety, can be found below. Sections in bold are new for FY2023.
I.C.19.e.5.(c) Underdosing
“Underdosing refers to taking less of a medication than is prescribed by a provider or manufacturer’s instruction. Discontinuing the use of a prescribed medication of 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”).
Documentation of a change in the patient’s condition is not required in order to assign an underdosing code.
Documentation that the patient is taking less of a medication than is prescribed or discontinued the prescribed medication is sufficient for code assignment.”
Codes for underdosing should never be assigned as principal or first-listed codes. If a patient has a relapse of 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.
Additional Information
The complete ICD-10-CM Official Guidelines for Coding and Reporting FY 2023 can be found on the CMS website by visiting the following link:
https://www.cms.gov/files/document/fy-2023-icd-10-cm-coding-guidelines.pdf
Additional information regarding underdosing can be found below:
- Coding Clinic, 1st 2022 Page: 36 “Underdosing with no change in patient’s condition”
- Coding Clinic, 4th 2003 Page: 81-82 “Insulin pump”
