If you work in healthcare or medical coding, you’ve probably encountered cases of low sodium. Knowing the correct ICD-10 code is important for accurate billing, clinical communication, and patient safety. Low sodium, also called hyponatremia, is not just a lab result. It can range from mild confusion to severe, life-threatening complications. This guide explains the ICD-10 code for low sodium (E87.1), when to use it, what documentation details matter, and how to avoid common coding mistakes.
What Is the ICD-10 Code for Low Sodium?
The official ICD-10-CM code for low sodium is E87.1. This code describes hypo-osmolality and hyponatremia, which means sodium levels in the blood are abnormally low.
There is also a neonatal-specific code, P74.22, which applies when a newborn is diagnosed with low sodium. This ensures more precise reporting in pediatric cases.
Why Accurate Coding Matters
Coding hyponatremia correctly is more than a paperwork task. It affects:
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Clinical safety: Misclassification could lead to overlooked treatment needs.
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Billing and reimbursement: Errors may delay claims or trigger audits.
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Data tracking: Public health data depends on accurate coding for electrolyte disorders.
In other words, coding low sodium properly ensures that both the patient’s care and the healthcare provider’s documentation are complete and correct.
Understanding Hyponatremia
Hyponatremia occurs when serum sodium falls below 135 mmol/L. Severe cases are often classified when sodium drops below 120 mmol/L.
Common Symptoms
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Mild cases: fatigue, headache, dizziness, confusion
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Severe cases: seizures, loss of consciousness, brain swelling, and in rare cases, coma
Types of Hyponatremia
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Hypovolemic: Sodium loss due to dehydration, vomiting, or diarrhea
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Euvolemic: Often linked to SIADH (Syndrome of Inappropriate Antidiuretic Hormone)
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Hypervolemic: Associated with heart failure, kidney disease, or liver cirrhosis
Understanding the type of hyponatremia helps physicians treat patients and supports coders in making precise notes.
Coding Strategy and Documentation Tips
When coding hyponatremia, follow these documentation principles:
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Use E87.1 when low sodium or hyponatremia is confirmed.
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Document lab values such as “serum sodium 128 mmol/L.”
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Note the onset: Is it acute or chronic?
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Record clinical signs: confusion, seizures, etc.
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Identify causes: medications, dehydration, SIADH, or organ failure.
When to Use P74.22
Use P74.22 only for newborns with documented low sodium. This separates pediatric coding from adult cases and improves accuracy.
Avoiding Common Errors
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Do not code dehydration (E86.0) unless it is clearly documented along with hyponatremia.
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Avoid vague entries like “low sodium” without supporting labs or clinical notes.
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Exclude SIADH (E22.2) unless it is specifically diagnosed. Hyponatremia should still be coded as E87.1 in these cases.
Clinical Example: Acute Hyponatremia
Correct documentation example:
“Patient presented with acute symptomatic hyponatremia. Sodium 122 mmol/L. Symptoms include seizures. Likely SIADH. Treatment started with 3% saline and fluid restriction.”
Incorrect documentation example:
“Low sodium. Started IV fluids.”
The difference is clear. The first provides lab results, timing, symptoms, and suspected cause, which supports accurate coding. The second is too vague and risks coding errors.
Treatment Overview
Treatment for hyponatremia depends on the severity:
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Mild or chronic cases: Fluid restriction, dietary adjustments, or stopping diuretics.
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Acute or severe cases: Slow correction using intravenous saline solutions (such as 3% NaCl). Patients require close monitoring to avoid complications.
A critical caution: correcting sodium too quickly can cause osmotic demyelination syndrome or central pontine myelinolysis, both serious neurological emergencies. That’s why detailed documentation and careful clinical management are essential.
Summary Table
| Focus Area | Details |
|---|---|
| Primary ICD-10 Code | E87.1 – Hypo-osmolality and hyponatremia |
| Neonatal Code | P74.22 – Neonatal hyponatremia |
| Key Documentation | Lab values, symptoms, timing, suspected cause |
| Coding Pitfalls | Avoid vague notes, only code dehydration if separately documented |
| Clinical Significance | May cause confusion, seizures, coma; requires prompt management |
| Treatment | Fluid restriction, controlled sodium correction, address underlying cause |
FAQs
Q1. What is the ICD-10 code for low sodium?
The ICD-10 code for hyponatremia or low sodium is E87.1.
Q2. Is there a separate code for newborns?
Yes. Use P74.22 for neonatal hyponatremia.
Q3. Can I use both dehydration and hyponatremia codes together?
Yes, but only if both conditions are clearly documented. If only hyponatremia is noted, use E87.1.
Q4. What should documentation include for coding?
Lab results, symptoms, timing (acute vs chronic), and suspected cause should all be included.
Q5. What is the difference between acute and chronic hyponatremia in coding?
Acute cases usually involve sudden drops in sodium with severe symptoms, while chronic cases develop slowly. Both are coded with E87.1 but should be clearly described in notes.
Conclusion
The ICD-10 code for low sodium is E87.1, and it should be used whenever hyponatremia is documented. For newborns, use P74.22. Accurate documentation of lab values, symptoms, and possible causes makes coding reliable and supports better patient care.
Whether you are a physician, coder, or healthcare administrator, always ensure that low sodium is recorded clearly and coded correctly. Proper coding not only streamlines reimbursement but also safeguards clinical accuracy.