Q&A: Coding anorexia nervosa

Q: How do you know which ICD-10-CM code to use to document a patient with anorexia nervosa?

A: Anorexia nervosa (F50.0-) has two specific types. There’s a fifth character to identify which type of anorexia nervosa: restricting type (F50.01) or binge eating/purging type (F50.02).

Restricting type means the patient is not eating. This is dieting to the max, fasting, and/or excessive exercise. And, of course, this has to be the determination of the physician; therefore, it needs to be documented what their determination is.

Binge eating/purging type is recurrent episodes of binge eating. This means eating like the food was going out of style and/or purging, which is self-induced evacuation of the body, sometimes by vomiting or misuse of laxatives, diuretics, and enemas.

How will you know which one it is, restricting type or binge eating/purging type? The physician must document if the patient is not eating, exercising excessively, etc., or doing massive elimination. And we know that this takes its toll on the body. For example, regular purging will show its effects on the teeth, and it becomes quite obvious after a period of time. This might be something that you’ll want to do a quick education on with your physician, especially your primary care physicians, who are not going to necessarily see this that often. However, when they do see it, we need them to be on top of this and document it.

As of 2025, a sixth character for these codes is required to identify the level of severity of anorexia nervosa. For restricting type, there are now five levels of severity, determined by the patient’s body mass index (BMI). They are:  

• Mild (F50.010), for a BMI greater than or equal to 17 kg/m²
• Moderate (F50.011), for a BMI of 16.0–16.99 kg/m²
• Severe (F50.012), for a BMI of 15.0–15.99 kg/m²
• Extreme (F50.013), for a BMI of less than 15.0 kg/m²
• In remission (F50.014)
  
  • Full remission (i.e., no criteria have been met for a sustained period )
  • In partial remission (i.e., low body weight criterion met but others still present)

Anorexia nervosa binge eating/purging type has the same criteria:

• Mild (F50.020), for a BMI greater than or equal to 17 kg/m²
• Moderate (F50.021), for a BMI of 16.0–16.99 kg/m²
• Severe (F50.022), for a BMI of 15.0–15.99 kg/m²
• Extreme (F50.023), for a BMI of less than 15.0 kg/m²
• In remission (F50.024)
  
  • Full remission (i.e., no criteria have been met for a sustained period)
  • In partial remission (i.e., low body weight criterion met but others still present)

As medical coding specialists, the good news is that we don't need the physician to document the words “mild, moderate, severe, or extreme” because it is directly identified by the BMI. Make sure that your patient charts identify a BMI, and the weight is tracked in the electronic health record. There may be an opportunity in your electronic health record to do the trending and calculate the patient’s BMI.

Editor’s note: This information was provided by Shelley C. Safian, PhD, MAOM, RHIA, CCS-P, CPC-I, an AHIMA-approved ICD-10-CM/PCS trainer and president of Safian Communications Services Inc., during the JustCoding webinar, “2025 ICD-10-CM Coding for Eating Disorders.” This Q&A originally appeared in JustCoding.