---
title: "ICD-10-CM K59.1: Functional diarrhea | BillingBrief"
description: "ICD-10-CM code K59.1: Functional diarrhea. Category, related codes, and the official source, in plain English."
canonical: "https://billingbrief.com/icd10/k59.1/"
language: "en"
---

# K59.1 Functional diarrhea

ICD-10-CM · [CMS code reference](#source)

**Official ICD-10-CM description:** Functional diarrhea

## Coding notes

From the ICD-10-CM FY2027 (effective October 1, 2026) tabular list. Notes on a parent code or category apply here too.

### Excludes1

Not coded together with this code. The exception is when the two conditions are unrelated to each other.

-   diarrhea NOS ([R19.7](https://billingbrief.com/icd10/r19.7/))
-   irritable bowel syndrome with diarrhea ([K58.0](https://billingbrief.com/icd10/k58.0/))
-   change in bowel habit NOS ([R19.4](https://billingbrief.com/icd10/r19.4/))
-   intestinal malabsorption (K90.-)
-   psychogenic intestinal disorders (F45.8)

### Excludes2

Not part of this code, but both can be coded when both are documented.

-   functional disorders of stomach (K31.-)

## Related codes

-   [`K59.02` Outlet dysfunction constipation ICD-10-CM](https://billingbrief.com/icd10/k59.02/)
-   [`K59.03` Drug induced constipation ICD-10-CM](https://billingbrief.com/icd10/k59.03/)
-   [`K59.04` Chronic idiopathic constipation ICD-10-CM](https://billingbrief.com/icd10/k59.04/)
-   [`K59.09` Other constipation ICD-10-CM](https://billingbrief.com/icd10/k59.09/)
-   [`K59.2` Neurogenic bowel, not elsewhere classified ICD-10-CM](https://billingbrief.com/icd10/k59.2/)
-   [`K59.31` Toxic megacolon ICD-10-CM](https://billingbrief.com/icd10/k59.31/)
-   [`K59.39` Other megacolon ICD-10-CM](https://billingbrief.com/icd10/k59.39/)
-   [`K59.4` Anal spasm ICD-10-CM](https://billingbrief.com/icd10/k59.4/)

## Common questions

### Is K59.1 a billable code?

Yes. K59.1 is a billable ICD-10-CM code in the ICD-10-CM FY2027 (effective October 1, 2026) code set.

## From the source

Official description from [CMS](https://www.cms.gov/medicare/coding-billing/icd-10-codes).
ICD-10-CM FY2027 (effective October 1, 2026).

Code set

ICD-10-CM

Category

K59 Other functional intestinal disorders

Chapter

Diseases of the digestive system

Billable

Yes

Educational reference only. Not medical, legal, or billing advice. Always check the current official code set and payer policy before you bill. [About BillingBrief and our sources](https://billingbrief.com/about/).