M79.7 is the single billable ICD-10-CM code covering fibromyalgia, a chronic nonarticular musculoskeletal syndrome marked by widespread myalgia and multiple tender points. It also captures the synonymous terms fibromyositis, fibrositis, and myofibrositis under its 'Applicable To' annotations.

Documentation tips

What should appear in the chart to support M79.7.

Source · Editorial brief grounded in 4 cited references ↓

• The provider must use the word 'fibromyalgia' (or a documented synonym such as fibromyositis or fibrositis) in the assessment — symptom descriptions alone do not support M79.7.
• Document the clinical basis for the diagnosis: widespread pain duration, tender point findings or ACR criteria, and exclusion of other musculoskeletal or rheumatic conditions.
• If chronic pain is separately addressed at the same encounter, document it as a distinct condition with its own treatment plan to justify a secondary G89.2x code.
• Record any comorbidities (sleep disturbance, fatigue, depression) that were evaluated or managed during the visit — they may support additional codes and medical necessity for multimodal treatment.
• Note prior workup results (labs, imaging) that ruled out inflammatory arthritis or other competing diagnoses, reinforcing the fibromyalgia diagnosis and audit defensibility.

Related CPT procedures

Procedure codes commonly billed with M79.7. Linking the right diagnosis to the right procedure is what establishes medical necessity.

Source · CMS LCDs · AAOS specialty guidance · claims-pattern analysis

Common coding pitfalls

The recurring mistakes coders make with M79.7 and adjacent codes.

Source · Editorial brief grounded in CDC ICD-10-CM tabular guidance, AAOS coding references, and cited references ↓

• Coding M79.7 alongside M79.1 (myalgia) or M79.0 (rheumatism, unspecified) on the same claim violates the Excludes1 relationship — choose only M79.7 when fibromyalgia is the documented diagnosis.
• Using M79.7 based on the patient's self-reported symptom history without an explicit physician diagnosis in the assessment/plan section will not withstand a payer audit.
• Assuming additional subcodes exist for laterality or severity — M79.7 is the terminal code with no further breakdown; do not append modifiers to create false specificity.
• Failing to sequence M79.7 correctly when it is a comorbidity: if the visit is for a knee or hip condition, that condition should be the principal diagnosis with M79.7 listed secondarily.
• Conflating fibromyalgia with myofascial pain syndrome in documentation — myofascial pain syndrome maps to M79.1x- (myalgia), not M79.7, unless the provider explicitly documents fibromyalgia.

Clinical context

Source · Editorial summary grounded in 4 cited references ↓

Inclusion & exclusion notes

Per the official ICD-10-CM Tabular List.

Source · CDC ICD-10-CM Official Tabular List · 2026

Sibling codes

Other billable codes under M79 (laterality / anatomic variants).