Diseases of the Musculoskeletal System and Connective Tissue
ICD-10 Code: M79.1
Myalgia
Muscle pain (myalgia) without specification of location or underlying cause, representing diffuse or localized muscle pain that doesn't fit more specific diagnostic categories.
Clinical Information
Myalgia (muscle pain) is an extremely common symptom with diverse etiologies including viral infections (influenza, COVID-19), overuse/strain, medication side effects (statins), fibromyalgia, polymyalgia rheumatica, autoimmune conditions, and metabolic disorders. M79.1 is used when muscle pain is documented but specific cause or location isn't specified.
Viral myalgia is particularly common with influenza and COVID-19, presenting as diffuse body aches. Medication-induced myalgia (especially statins) affects 5-10% of users. Evaluation includes pain distribution, associated symptoms (fever, weakness, rash), medication review, and laboratory testing (CK, ESR, thyroid function) if indicated.
Coding Guidelines
- 1Use M79.1 for non-specific muscle pain without identified etiology
- 2If specific muscle group is painful, consider site-specific codes
- 3For statin-induced myalgia, also code T46.6X5A (adverse effect of statins)
- 4For viral myalgia, code underlying infection (J10.1 influenza, U07.1 COVID-19) as primary with M79.1 as secondary
- 5Do NOT use for myositis (M60.x) or fibromyalgia (M79.7) - use specific codes
Common Uses
- Influenza with body aches and muscle pain
- Patient on statin therapy reporting muscle pain, CK normal
- Post-viral syndrome with persistent myalgia
- Generalized muscle aches without specific diagnosis
Related ICD-10 Codes
M79.7Fibromyalgia (use for chronic widespread pain with tender points)
M60.9Myositis, unspecified (use if inflammation present)
M35.3Polymyalgia rheumatica
J10.1Influenza with respiratory manifestations (code first for flu-related myalgia)
Documentation Requirements
- Document 'myalgia,' 'muscle pain,' or 'muscle aches'
- Note distribution: diffuse vs. localized
- Associated symptoms: fever, weakness, stiffness
- Recent viral illness or medication changes (especially statins)
- CK level if checked
Real-World Coding Examples
Patient with influenza presents with fever, cough, and diffuse body aches. Diagnosis: Influenza (J10.1), Myalgia (M79.1).
Follow-up for patient on atorvastatin reporting muscle pain x 2 weeks. CK normal. Diagnosis: Myalgia (M79.1), Adverse effect of HMG-CoA reductase inhibitors (T46.6X5A). Plan: Stop statin, recheck in 2 weeks.
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