Q&A: Reporting BMI in ICD-10-CM

Q: Can an ICD-10-CM body mass index (BMI) code be used as a standalone code? If not, what documentation should we look for to justify the use of a BMI code?

A: The 2019 ICD-10-CM Official Guidelines for Coding and Reporting state you cannot use a BMI code (found in ICD-10-CM code category Z68.-) alone. BMI codes need to be supported as medically relevant by an associated diagnosis that is considered a reportable diagnosis. 

Coders must remember that BMI codes were never intended to be used as standalone codes. I know this can be an issue since the various types of reimbursement methodologies, such as risk adjustment, include the BMI codes, but these codes were always meant to be accompanied by a corresponding diagnosis code.

Coding Clinic, Fourth Quarter 2018, specifically states that the provider must provide documentation of a clinical condition such as obesity or overweight to justify the reporting of a code for BMI.

I have been asked if there could be situations where another weight-related diagnosis, such as sleep apnea, diabetes, or hypertension, could make the use of a BMI code relevant. According to Coding Clinic, Fourth Quarter 2018, the ICD-10-CM manual does not identify a list of conditions that can be considered associated with a BMI. To me, this means that as long as the documentation clearly links the condition to BMI, it would be considered clinically relevant. 

For patients with provider documentation identifying “morbid” obesity, the code E66.01 (morbid [severe] obesity due to excess calories) can be assigned even if the BMI is not greater than 40, per Coding Clinic.  As noted in the 2019 ICD-10-CM Official Guidelines for Coding and Reporting, Section I.A.19, “The assignment of a diagnosis code is based on the provider’s diagnostic statement that the condition exists. The provider’s statement that the patient has a particular condition is sufficient. Code assignment is not based on clinical criteria used by the provider to establish the diagnosis.” 

This guidance is important since there are some situations where a patient can have severe or morbid obesity with a BMI of 35-39.9 due to co-existing comorbid conditions. In an inpatient setting, only the obesity BMI codes for 40-plus are considered CC conditions but note that E66.01 is does group to the Hierarchical Condition Categories for risk-adjustment purposes. 

Editor’s note: Shannon McCall, RHIA, CCS, CCS-P, CPC, CEMC, CRC, CCDS, HCS-D, director of HIM and coding for HCPro in Middleton, Massachusetts, answered this question.

This answer was provided based on limited information. Be sure to review all documentation specific to your own individual scenario before determining appropriate code assignment.

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