Parsing Overweight and Obesity Coding

Tune in to this monthly online coding column, facilitated by AHIMA’s coding experts, to learn about challenging areas and documentation opportunities for ICD-10-CM/PCS.

By Elena Miller, MPH, RHIA, CCS


According to the National Institutes of Health (NIH), obesity has emerged as a leading public health concern in the United States and it has been well-established that people who are obese face increased risks of death from heart disease, stroke, and certain cancers. While not much has changed in the way we code for this condition, with all the buzz around Hierarchical Condition Categories (HCCs), obesity and body mass index (BMI) have become a popular topic. It is also a topic that is brought up in conversations about inpatient DRG coding denials.

Per the Centers for Disease Control and Prevention (CDC), weight that is higher than what is considered as a healthy weight for a given height is described as overweight or obese. BMI, a number calculated based on these two factors, is used as a screening tool for identifying patients that are overweight or obese. Generally, a BMI of over 30 is considered obese.

Obesity is frequently subdivided into categories:1

  • Class 1: BMI of 30 to < 35
  • Class 2: BMI of 35 to < 40
  • Class 3: BMI of 40 or higher; Class 3 obesity is sometimes categorized as “morbid,” “extreme,” or “severe” obesity

HCC 22 is titled Morbid Obesity and it is specific to “morbid obesity.” The category includes the following codes:

  • E6601, Morbid (severe) obesity due to excess calories
  • E662, Morbid (severe) obesity with alveolar hypoventilation
  • Z6841, Body mass index (BMI) 40.0-44.9, adult
  • Z6842, Body mass index (BMI) 45.0-49.9, adult
  • Z6843, Body mass index (BMI) 50-59.9, adult
  • Z6844, Body mass index (BMI) 60.0-69.9, adult
  • Z6845, Body mass index (BMI) 70 or greater, adult

This is where it gets interesting. NIH defines morbid obesity as being 100 pounds or more above the ideal body weight; or having a BMI of 40 or greater; or having a BMI of 35 or greater and one or more comorbid conditions. Note that in the list above, there are no codes listed for a BMI of 35.0 to 39.9. That is because a BMI of 35.0 – 39.9 is not generally considered morbidly obese. The physician needs to determine whether the patient has comorbid conditions and if so, will then document “morbid obesity.” Coding professionals may not make this determination on their own. If the medical record documentation supports a query, then one should be sent.

On the flip side, the denials conversation is different. The actual obesity code does not impact the DRG. The financial impact results from assigning a code for a BMI of over 40. Coding guidelines are very clear that an associated condition (i.e, overweight, obesity, etc.) needs to be documented in the record to support the code assignment for BMI. The third quarter 2011 issue of Coding Clinic addresses the clinical significance of obesity and states the following:

“Individuals who are overweight, obese or morbidly obese are at an increased risk for certain medical conditions when compared to persons of normal weight. Therefore, these conditions are always clinically significant and reportable when documented by the provider. In addition, the body mass index (BMI) code meets the requirement for clinical significance when obesity is documented. Refer to Coding Clinic, Third Quarter 2007, pages 13-14, for additional information on coding chronic conditions.”

The issue of Coding Clinic referenced in the quoted material above states:

“Chronic conditions such as, but not limited to, hypertension, Parkinson’s disease, COPD, and diabetes mellitus are chronic systemic diseases that ordinarily should be coded even in the absence of documented intervention or further evaluation. Some chronic conditions affect the patient for the rest of his or her life and almost always require some form of continuous clinical evaluation or monitoring during hospitalization, and therefore should be coded.”

While it seems clear that obesity and the associated BMI are considered clinically significant and should be reported when documented, some payors are holding this condition to the “additional diagnosis” guideline and stating that it should only be coded when it meets that definition for reporting (i.e. treated, clinically evaluated, etc.). In an unpublished response from Coding Clinic, it was confirmed that obesity/BMI are clinically supported and should be reported when documented regardless of intervention. That is a battle that providers will have to continue to fight through the appeals process.

  1. Centers for Disease Control and Prevention. Defining Adult Overweight and Obesity.


Elena Miller is the director of coding audit and education at a healthcare system.


  1. We are seeing a lot of ‘super obesity’ documented on patients with BMI >50, admitted for gastric surgery. Coding it to ‘other’ obesity lacks the description we are looking for. Assuming we can’t code it to ‘morbid’ obesity since it’s not described that way, can we code it to ‘severe’ obesity?

    Thank you

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  2. To be honest, I’m not sure. I have received mixed messages from the coding clinic on various topics. In one response, they will say that something is implied and can be coded even though it is not indexed. In another, they will say that we need to query because the specific wording is not indexed. You may want to to send a letter in to the Coding Clinic with that question.

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  3. Does the co-morbid condition need to be linked with the obesity? For example, “Pt with Severe obesity, BMI of 38.3 pt also with HTN.” Or can the Pt have documented HTN and the Provider document in the assessment “Pt. presents with morbid obesity..It is of severe intensity. BMI 38.3”

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