2026 ICD-10-CM Diagnosis Code M45Ankylosing spondylitis

ICD-10-CM CodesM00–M99M45-M49M45

ICD-10-CM M45
CMSSource: CMS FY 2026 ICD-10-CM dataset · Effective Oct 1, 2025 – Sep 30, 2026

M45 is a non-billable ICD-10-CM category code for ankylosing spondylitis, so it cannot be submitted on claims. Use a more specific code from this category instead, such as M45.0, M45.1, M45.2, and M45.3.

Code Identity

ICD-10-CM Code
M45
Billable Status
No — Non-Billable Category
Code Describes
Ankylosing spondylitis
Chapter
M45-M49
Spondylopathies

Code Classification

ChapterM00–M99Diseases of the musculoskeletal system and connective tissue
SectionM45-M49Spondylopathies
CategoryM45Ankylosing spondylitis
This CodeM45Ankylosing spondylitis

Specific Coding for Ankylosing spondylitisOverview

Non-specific codes like M45 require more characters. Use one of these billable codes instead:

  • Use M45.0 for Ankylosing spondylitis of multiple sites in spine

  • Use M45.1 for Ankylosing spondylitis of occipito-atlanto-axial region

  • Use M45.2 for Ankylosing spondylitis of cervical region

  • Use M45.3 for Ankylosing spondylitis of cervicothoracic region

  • Use M45.4 for Ankylosing spondylitis of thoracic region

  • Use M45.5 for Ankylosing spondylitis of thoracolumbar region

  • Use M45.6 for Ankylosing spondylitis lumbar region

  • Use M45.7 for Ankylosing spondylitis of lumbosacral region

  • Use M45.8 for Ankylosing spondylitis sacral and sacrococcygeal region

  • Use M45.9 for Ankylosing spondylitis of unspecified sites in spine

  • M45.A for Non-radiographic axial spondyloarthritis

  • Use M45.A0 for Non-radiographic axial spondyloarthritis of unspecified sites in spine

  • Use M45.A1 for Non-radiographic axial spondyloarthritis of occipito-atlanto-axial region

  • Use M45.A2 for Non-radiographic axial spondyloarthritis of cervical region

  • Use M45.A3 for Non-radiographic axial spondyloarthritis of cervicothoracic region

  • Use M45.A4 for Non-radiographic axial spondyloarthritis of thoracic region

  • Use M45.A5 for Non-radiographic axial spondyloarthritis of thoracolumbar region

  • Use M45.A6 for Non-radiographic axial spondyloarthritis of lumbar region

  • Use M45.A7 for Non-radiographic axial spondyloarthritis of lumbosacral region

  • Use M45.A8 for Non-radiographic axial spondyloarthritis of sacral and sacrococcygeal region

  • Use M45.AB for Non-radiographic axial spondyloarthritis of multiple sites in spine

Tabular List NotesGuidance

Coding notes and annotation back-references applicable to this code.

Inclusion Terms

  • Rheumatoid arthritis of spine

Type 1 Excludes

  • arthropathy in Reiter's disease M02.3
  • juvenile ankylosing spondylitis M08.1

Type 2 Excludes

  • Behçet's disease M35.2

Patient EducationClinical

Ankylosing Spondylitis

Ankylosing spondylitis (AS) is a type of arthritis of the spine. It causes inflammation (swelling) between your vertebrae (the bones that make up your spine) and the joints between your spine and pelvis. AS inflammation can cause stiffness and make it difficult to move and bend.

The full article covers:

  • What is ankylosing spondylitis?
  • Who is more likely to get ankylosing spondylitis?
  • What causes ankylosing spondylitis?
  • What are the symptoms of ankylosing spondylitis?
  • How is ankylosing spondylitis diagnosed?
  • What are the treatments for ankylosing spondylitis?

Read the full article at MedlinePlus

Courtesy of MedlinePlus, a service of the U.S. National Library of Medicine.

Code HistoryHistory

FY 2016AddedAdded to the ICD-10-CM code setEffective October 1, 2015, the first year of ICD-10-CM.
FY 2017–2025No changes
FY 2026CurrentCurrent code set, no changesEffective October 1, 2025 through September 30, 2026.

Questions About M45Overview

Is M45 (Ankylosing spondylitis) a billable code?

No. This is a category header that groups the codes for ankylosing spondylitis, and headers cannot be submitted on claims. Claims for ankylosing spondylitis need a more specific code from this category, such as M45.0, M45.1, and M45.2.