Basics of Body Mass Index (BMI) ICD-10 code

BMI describes patients’ body weight in consideration of their height. The patient’s weight in kilograms is divided by the square of the patient’s height in meters (kg/m²). A high BMI can be an indicator of overweight or obesity; a low BMI may indicate cachexia or malnutrition.

Some people, such as athletes, can fall into high BMI ranges without actually being overweight. For example, bodybuilders may have very high BMIs while having low body fat. For this reason, the BMI codes (Z68.-) can be coded based on documentation from clinicians other than the provider, BUT the provider must supply a diagnosis associated with a weight-based/nutritional disorder to justify the reporting of the BMI.

BMI codes are reported via code grouping Z68. BMI adult codes (Z68.20–X68.45) are assigned to individuals age 20 years or older. BMI pediatric codes (Z68.51–Z68.54) are assigned to individuals ages 2–19 years. Pediatric BMI is based on growth chart percentiles published by the Centers for Disease Control and Prevention.

BMI codes should only be assigned when there is an associated, reportable diagnosis (such as obesity). Do not assign BMI codes during pregnancy.

Body Mass Index (BMI) ICD 10 coding Guidelines

Nutritional disorders, such as deficiencies of specific vitamins and minerals, are classified in
categories E40 through E64, with the exception of nutritional anemias, which are classified in
categories D50 through D53.
Several codes are used to identify overweight and obesity, including the following:

E66.01 Morbid (severe) obesity due to excess calories
E66.09 Other obesity due to excess calories
E66.1 Drug-induced obesity
E66.2 Morbid (severe) obesity with alveolar hypoventilation
E66.3 Overweight
E66.8 Other obesity
E66.9 Obesity, unspecified

These codes are assigned only on the basis of the physician’s diagnostic statement. Category E66, Overweight and obesity, requires the assignment of an additional code (Z68.-) for the body mass index (BMI), if known. BMI is a measure of weight for height used as a tool for indicating weight status in adults. Coding BMI is an exception to the guideline that requires that code assignment be based on the documentation by the provider. The BMI code assignment should be based on medical record documentation, which may be found in the notes of other clinicians involved in the care of the patient (i.e., physician or other qualified health care practitioner legally accountable for establishing the patient’s diagnosis). BMI is typically documented by the dietitian or the nurse. Although BMI may be reported on the basis of another clinician’s documentation, the codes for the associated diagnosis (such as overweight and obesity) must be based on the provider’s documentation.

Being overweight may place a patient at increased risk for certain medical conditions. However, overweight may only be reported when it meets the definition of a reportable diagnosis per Section III, Reporting Additional Diagnoses, of the ICD-10-CM Official Guidelines for Coding and Reporting. Neither the code for overweight nor the BMI code is assigned when there is no documentation that the diagnosis “overweight” meets the definition of a reportable secondary diagnosis. Obesity and morbid obesity are always clinically significant and should be coded and reported when documented by the provider. The BMI code may be reported with these conditions when BMI is documented. BMI codes should not be assigned during pregnancy.

Occasionally, a patient’s BMI may fluctuate during a hospital stay. If the BMI fluctuation is linked to a clinically significant condition, such as malnutrition or anorexia nervosa, code the most severe BMI value recorded during the admission. However, the BMI codes are not intended to report changes in BMI caused by fluid overload/retention. BMI fluctuation caused by weight gain due to excess fluid is not the same as that caused by loss or gain of body mass; weight from excess fluid can lead to an overestimate of the BMI, making it an inaccurate indicator of the patient’s actual weight status