M79.10

🧬 ICD-10 CM M79.10 — Myalgia, Unspecified Site

Billable Code Confirmed

ICD-10 CM M79.10 is a complete, five-character ICD-10-CM code and is fully billable on inpatient and outpatient claims for FY2026.³ The final “0” indicates that the muscle pain is not attributed to a specific anatomic site, distinguishing it from M79.11 and M79.12, which specify mastication and head/neck auxiliary muscles respectively.

Non-Billable Parent Codes

M79.1 is a non-billable, four-character category header that requires a fifth character for site specificity and cannot be reported on any claim.⁴ M79 is likewise a non-billable three-character category that groups all “other and unspecified soft tissue disorders” and must never be used for HIPAA-covered transactions.

Clinical Context

Providers select M79.10 when a patient reports diffuse or generalized muscle pain without a documented single muscle group, trigger point, or underlying disease process driving the discomfort.

Code Classification

ICD-10 CM M79.10 is a diagnosis code used to classify a symptom-level muscular pain complaint; it is not a procedure code and carries no inherent HCC weight or DRG severity impact.

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🔍 Code Description

ICD-10 CM M79.10 belongs to the M79.1 subcategory of myalgia codes, itself nested within the broader M79 category of “Other and unspecified soft tissue disorders” in the M70-M79 block. This “unspecified site” code was introduced alongside its siblings, M79.11 and M79.12, to replace the older, less specific parent code and push documentation toward greater site-level detail whenever possible.

Coders should reserve M79.10 for cases where the medical record genuinely lacks anatomic detail, since payers and quality reviewers increasingly expect providers to document the specific muscle group involved. When myalgia is linked to a known cause such as statin therapy, the underlying drug reaction code should be reported in addition to or instead of M79.10 depending on documentation, and should never be confused with M79.7 fibromyalgia, which requires distinct diagnostic criteria involving widespread pain over three months.

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🌳 Code Tree / Hierarchy

M79 Other and unspecified soft tissue disorders, not elsewhere classified ❌ Non-billable
│
├── M79.0 Rheumatism, unspecified ✅ Billable
├── M79.2 Neuralgia and neuritis, unspecified ✅ Billable
│
├── M79.1 Myalgia ❌ Non-billable
│ │
│ ├── M79.10 Myalgia, unspecified site ◀ THIS CODE ✅ Billable
│ ├── M79.11 Myalgia of mastication muscle ✅ Billable
│ ├── M79.12 Myalgia of auxiliary muscles, head and neck ✅ Billable
│ └── M79.18 Myalgia, other site ✅ Billable
│
└── M79.7 Fibromyalgia ✅ Billable

Specificity Matters

Payers increasingly scrutinize repeated use of M79.10 without site-level detail, since M79.18 (myalgia, other site) or M79.12 often better reflect the documented presentation and support medical necessity for targeted treatment.

Tip

Always confirm the record does not support a more specific site code, such as M79.11 or M79.18, before defaulting to the unspecified M79.10 option.

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✅ Includes

• Chronic musculoskeletal pain without a documented specific site
• Chronic musculoskeletal pain due to disease classified elsewhere, when the site is not further specified
• Generalized muscle aching reported by the patient without an identifiable trigger point or muscle group

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❌ Excludes

Excludes 1

• M79.7 — Fibromyalgia is a distinct chronic widespread pain syndrome requiring specific diagnostic criteria and cannot be coded together with M79.10.
• M60.- — Myositis represents true muscle inflammation with distinct pathophysiology and diagnostic workup, and this code family requires additional characters to be billable.

Danger

The most common Excludes1 error occurs when a provider documents “myositis-type myalgia,” prompting coders to default to M79.10 instead of correctly identifying and coding the specific myositis subtype under M60.-.

Excludes 2

• None identified for M79.10 in the FY2026 ICD-10-CM tabular list.⁴

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📋 Clinical Overview

Unspecified Site vs. Site-Specific Myalgia

M79.10 and its siblings M79.11, M79.12, and M79.18 all describe muscle pain, but differ entirely in the degree of anatomic detail available in the documentation.

Feature	M79.10	M79.12	M79.18
Primary symptom	Generalized muscle pain without a documented site.	Muscle pain isolated to head and neck auxiliary muscles.	Muscle pain in a documented site not covered by other M79.1- codes.
Diagnostic specificity	Lowest; used only when no site can be determined.	Moderate to high; anatomic region is clearly documented.	High; site is known but falls outside mastication or head/neck codes.
Typical care setting	Primary care, urgent care.	Dental, TMJ, ENT specialty clinics.	Orthopedics, sports medicine, physical therapy.

Important

A CDI trigger should fire whenever “generalized myalgia” appears without any documented physical exam findings pointing to a specific muscle group, since this often signals an opportunity to query for more precise site-level detail.

Manifestations & Symptom Burden

• Diffuse muscle soreness not localized to a single anatomic region.
• Fatigue accompanying muscular discomfort in the absence of a confirmed inflammatory process.
• Reduced range of motion secondary to generalized muscle pain rather than joint pathology.

Tip

Manifestation-level symptoms such as fatigue or stiffness should not be separately coded when they are integral to the myalgia presentation; only code them separately if documented as distinct, unrelated findings.

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💰 HCC Risk Adjustment

ICD-10 CM M79.10 does not map to any CMS-HCC category under the current V28 model, meaning it carries no RAF value and has no impact on Medicare Advantage risk scores.¹ Coders should still capture it for clinical completeness but should prioritize identifying and documenting any underlying HCC-eligible condition driving the muscle pain whenever supported by the record.

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🏥 MS-DRG Assignment

ICD-10 CM M79.10 is not a CC or MCC and does not independently influence MS-DRG grouping or the assigned relative weight.² It is typically reported as a secondary diagnosis alongside the condition that actually justified inpatient admission, since generalized myalgia rarely meets inpatient severity thresholds on its own.

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🔗 Related ICD-10-CM Codes

Myalgia sibling group: M79.11 (myalgia of mastication muscle), M79.12 (myalgia of auxiliary muscles, head and neck), M79.18 (myalgia, other site).

Related soft tissue and rheumatologic alternatives: M79.0 (rheumatism, unspecified), M79.7 (fibromyalgia), M79.2 (neuralgia and neuritis, unspecified), M25.50 (pain in unspecified joint).

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🛠️ Commonly Associated CPT Codes

• 99213 — Established patient office visit, low complexity; frequently billed alongside M79.10 for routine myalgia follow-up.
• 99203 — New patient office visit, low complexity; used when M79.10 is first assigned during an initial evaluation.
• 97110 — Therapeutic exercise, 15 minutes; commonly reported when physical therapy is ordered for generalized muscle pain management.
• 36415 — Collection of venous blood by venipuncture; often billed when labs are drawn to rule out myositis or a metabolic cause of myalgia.

NCCI Bundling Considerations

Evaluation and management codes billed with a same-day venipuncture such as 36415 are generally payable together without modifier intervention, since venipuncture is not bundled into the E/M service. Therapeutic exercise codes like 97110 may require modifier -59 if performed alongside another timed therapy procedure on the same date to indicate a distinct service.

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🔬 ICD-10-PCS Crosswalk

ICD-10 CM M79.10 is a diagnosis code and has no direct ICD-10-PCS procedural crosswalk, since PCS codes classify inpatient procedures rather than symptom-based diagnoses.

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💊 Coding Scenarios and Examples

Scenario 1: A 45-year-old presents to primary care with two weeks of diffuse muscle soreness, no documented trigger point, and unremarkable labs. Correct coding: M79.10. Sequencing: reported as the primary diagnosis for this encounter since no specific site or cause is supported.

Scenario 2: A patient on statin therapy reports new generalized muscle aching, and the provider documents “statin-associated myalgia.” Correct coding: M79.10 with the adverse effect code for the statin sequenced per guideline requirements, since the site remains unspecified but the cause is now documented. CDI note: query for whether muscle enzyme testing supports a myopathy diagnosis instead.

Scenario 3: An inpatient admitted for a hip fracture also reports generalized myalgia unrelated to the injury during the stay. Correct coding: hip fracture code sequenced first, M79.10 listed as a secondary diagnosis. Sequencing explanation: M79.10 does not meet reporting criteria as a principal diagnosis here and carries no CC/MCC weight.

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⚠️ Coding Pitfalls and Tips

• Do not default to M79.10 simply because “myalgia” appears in the note; always check documentation for a specific site that would support M79.11, M79.12, or M79.18 instead.
• Remember the Excludes1 relationship with M79.7; fibromyalgia and unspecified myalgia cannot both be coded for the same encounter.
• ICD-10 CM M79.10 carries no HCC weight and no CC/MCC status, so it will not affect risk scores or DRG weighting.
• Never report the non-billable parent M79.1x or category M79 on a claim; always carry the code out to the full five characters.

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^{Sources: ¹CMS-HCC Model V28 Risk Adjustment Documentation, cms.gov · ²CMS MS-DRG Definitions Manual, FY2026 · ³CMS/NCHS ICD-10-CM FY2026 Tabular List, cms.gov · ⁴ICD-10-CM Official Guidelines for Coding and Reporting, FY2026}