Hand pain is a frequent reason patients seek medical care, and coders must assign the right ICD-10 code to capture the symptom accurately. For left-sided complaints, the correct ICD-10 code is M79.642, which belongs to the category Pain in hand and fingers.
Using this code correctly does more than secure reimbursement. It demonstrates medical necessity, reduces denials, and keeps records compliant. In this guide, you will learn when to use M79.642, when not to, related codes, documentation essentials, and real-world case applications.
What Does M79.642 Represent?
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Code: M79.642
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Description: Pain in left hand
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Category: Symptoms, signs, and abnormal clinical findings (Chapter 18, ICD-10-CM)
This code applies when pain is localized to the left hand but no specific diagnosis such as fracture, arthritis, or neuropathy has been established. Since it is a symptom code, it is usually temporary and may later be replaced by a confirmed condition once test results are available.
When to Use and When Not to Use M79.642
Correct Usage
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Provider documents pain in the left hand without identifying an underlying condition.
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Pain affects the entire hand rather than a single finger or specific joint.
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Laterality (left) is included in the note.
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The code is being used as a working diagnosis during the initial evaluation.
Incorrect Usage
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Finger-only pain → Use M79.645 (Pain in left finger(s)).
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Joint pain in the left hand → Use M25.542 (Pain in joints of left hand).
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Confirmed conditions → If arthritis, carpal tunnel syndrome, or a fracture is diagnosed, those codes take precedence.
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Missing laterality → If “left” is not documented, assign M79.643 (Pain in unspecified hand).
Related ICD-10 Codes for Hand Pain
| Code | Description | When to Use |
|---|---|---|
| M79.642 | Pain in left hand | General hand pain without specific diagnosis |
| M79.641 | Pain in right hand | Pain localized to right hand only |
| M79.645 | Pain in left finger(s) | Pain affects one or more fingers |
| M25.542 | Pain in joints of left hand | Pain is joint-specific |
| M79.643 | Pain in unspecified hand | Laterality not recorded |
Including these related codes improves coding accuracy and strengthens claim success rates.
Documentation Requirements for M79.642
Accurate coding depends on precise documentation. Providers should include the following details:
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Laterality: Specify “left hand.”
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Location: Palm, dorsum, or whole hand.
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Onset and duration: Acute vs chronic, with dates.
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Severity: Numeric scale (0–10) or descriptive terms.
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Associated findings: Swelling, numbness, tingling, or weakness.
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Functional impact: Activities affected, such as writing or lifting.
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Interventions: Imaging, therapy, or medication, with rationale.
Examples of Weak vs Strong Documentation
Weak: “Patient complains of hand pain.”
→ Missing laterality, severity, and onset.
Strong: “Patient reports severe throbbing pain in the left palm for 5 days. Pain worsens with typing, rated 7/10. Mild swelling and reduced grip strength observed. X-ray ordered to rule out fracture.”
This second example fully supports M79.642 and medical necessity for imaging.
Common Mistakes in Coding Left Hand Pain
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Using unspecified codes when laterality is clearly documented.
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Reporting symptom codes along with confirmed conditions without justification.
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Confusing finger pain with hand pain codes.
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Omitting onset or severity in provider notes.
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Ignoring payer requirements for medical necessity.
Real-World Case Scenarios
Case 1: Acute trauma with pending imaging
Note: “Patient fell on left hand yesterday, reports 8/10 pain across palm and dorsum. X-ray ordered.”
→ Code: M79.642 until imaging reveals a specific injury.
Case 2: Finger-only pain
Note: “Left index finger pain, sharp and intermittent, present for 1 week.”
→ Code: M79.645.
Case 3: Chronic pain with diagnosis
Note: “Chronic pain in left hand due to confirmed rheumatoid arthritis.”
→ Code: Rheumatoid arthritis (M06.9x) as primary. Symptom code only if provider documents it separately.
Case 4: Joint-focused pain
Note: “Pain in MCP joints of left hand, worsens with gripping objects.”
→ Code: M25.542.
Frequently Asked Questions
What is the ICD-10 code for left hand pain?
M79.642, used when pain is documented in the left hand without another confirmed condition.
Can M79.642 be used with other codes?
Yes, but avoid redundancy. Pair with other codes only if documentation supports it.
What if only one finger hurts?
Use M79.645 (Pain in left finger(s)).
How important is laterality in coding?
Very important. Without “left,” coders must assign M79.643 (unspecified hand), which is less precise and may lead to payer issues.
Does severity or chronicity change the ICD-10 code?
No, the base code remains M79.642. However, those details improve documentation quality and support.
Should I update the code if imaging shows arthritis?
Yes. Replace or supplement M79.642 with the confirmed diagnosis code, since condition codes take precedence.
Key Takeaway
The ICD-10 code for left hand pain, M79.642, should be used only when pain is documented in the left hand without a more precise diagnosis. To code correctly, providers must record laterality, location, onset, severity, and associated findings. Coders should always check if a specific condition code is available before assigning M79.642. With complete documentation and proper code selection, claims are more likely to be approved, providers are reimbursed faster, and patient care is accurately represented.