What is the ICD-10 code for ulcerative colitis?

The ICD-10-CM code for ulcerative colitis is K51.90 when documented without further specification. More specific documentation changes the code — see the scenario table.

Yes — K51.90 is a billable ICD-10-CM code, but payers expect the most specific code the documentation supports.

ICD-10 Code for ulcerative colitis

The ICD-10-CM code for ulcerative colitis is K51.90 when documented without further specification. HCC RxHCC Ulcerative colitis is coded by extent and complication status. K51.90 is unspecified UC without complications; specific forms such as pancolitis (K51.0-) and proctitis (K51.2-), plus complication codes for bleeding, obstruction, fistula, or abscess, apply when documented.

K51.90 is a risk-adjusting diagnosis under CMS-HCC and RxHCC models. Create a free account to see model versions, RAF contribution, and AI-powered HCC suppression analysis.

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Symptom code vs. confirmed diagnosis

Ulcerative colitis is a diagnosis, not a symptom; the documented extent (e.g., pancolitis, proctitis) and any complication drive the code rather than the unspecified K51.90.

Which Code Should You Use?

K51.90 ✓ Billable — Ulcerative colitis, unspecified, without complications

Ulcerative colitis, unspecified, without complications.

K51.00 ✓ Billable — Ulcerative (chronic) pancolitis without complications

Ulcerative (chronic) pancolitis without complications.

K51.011 ✓ Billable — Ulcerative (chronic) pancolitis with rectal bleeding

Ulcerative (chronic) pancolitis with rectal bleeding.

K51.012 ✓ Billable — Ulcerative (chronic) pancolitis with intestinal obstruction

Ulcerative (chronic) pancolitis with intestinal obstruction.

K51.013 ✓ Billable — Ulcerative (chronic) pancolitis with fistula

Ulcerative (chronic) pancolitis with fistula.

What to Document

Extent/type - pancolitis (K51.0-), proctitis (K51.2-), or other specified form - drives the subcategory.
Complications when present (rectal bleeding, intestinal obstruction, fistula, abscess).
Ulcerative colitis versus Crohn's disease - distinct diagnoses.

Common Documentation Pitfalls

Don't stay on K51.90 when the extent (pancolitis, proctitis) is documented.
When a complication (bleeding, obstruction, fistula, abscess) is documented, code the complication-specific form, not the "without complications" code.

Also Known As

Official ICD-10-CM Alphabetic Index terms that point to K51.90:

Colitis (acute) (catarrhal) (chronic) (noninfective) (hemorrhagic) › ulcerative (chronic)
Arthropathy › in (due to) › ulcerative colitis NEC

Coding Notes

K51.90 is unspecified ulcerative colitis without complications. Documenting the extent (pancolitis K51.0-, proctitis K51.2-) and any complication (rectal bleeding, obstruction, fistula, abscess) yields a more specific code. Ulcerative colitis and Crohn's disease are separate categories.