Hyponatremia ICD 10 Code: Fast-Track Diagnosis & Coding
Introduction
Hyponatremia is more than a coding detail—it’s a potentially life-threatening condition. If not diagnosed and coded correctly, it can lead to clinical errors and insurance claim denials.
This article simplifies the entire process—from understanding symptoms to entering the correct ICD-10 code. Whether you’re a clinician or a medical coder, this is your go-to guide for accurate and compliant documentation.
Let’s dive in with the essentials.
What Is Hyponatremia?
Low Sodium, Big Risk
Hyponatremia means low sodium levels in the blood, typically below 135 mmol/L. This imbalance can quickly spiral into confusion, seizures, or even coma if not treated promptly.
Common Symptoms
- Fatigue
- Headache
- Confusion
- Muscle weakness
- Seizures
Causes of Hyponatremia
Understanding Root Triggers
Hyponatremia doesn’t just happen—it’s often a result of underlying health problems or medications.
- Heart failure
- Liver cirrhosis
- Chronic kidney disease (CKD)
- Diuretics or SSRIs
- SIADH (syndrome of inappropriate antidiuretic hormone secretion)
ICD-10 Code for Hyponatremia Explained
E87.1 – The Official Code
| ICD-10 Code | Description | Notes |
|---|---|---|
| E87.1 | Hyponatremia | Use when sodium <135 mmol/L |
This code falls under the E87 category for “Other Disorders of Fluid, Electrolyte and Acid-Base Balance.”
Key Documentation Requirements
- Confirm low sodium via lab report
- Link to a clinical symptom or diagnosis
- Specify acute vs. chronic if known
When to Use E87.1
Case Example:
Patient: Female, 68, presenting with dizziness and disorientation. Sodium level: 124 mmol/L.
Diagnosis: Hyponatremia due to thiazide diuretics
ICD-10: E87.1
Secondary Code: I10 for hypertension
Bullet Checklist: Proper ICD-10 Usage
- ✅ Is serum sodium <135?
- ✅ Is a medical diagnosis clearly stated?
- ✅ Is the cause documented (e.g., meds, CHF)?
- ✅ Use E87.1 for primary diagnosis if relevant
- ✅ Add coexisting conditions for full clarity
Advanced Coding Scenarios
Coexisting Conditions to Code Together
| ICD-10 Code | Condition | When to Use |
|---|---|---|
| I50.9 | Heart Failure (unspecified) | If cause is cardiac |
| E22.2 | SIADH | When hormone imbalance confirmed |
| N18.9 | CKD | If renal issues present |
| F03.90 | Dementia (unspecified) | For elderly patients with confusion |
Pro Tip: Always link secondary conditions to the primary diagnosis if causality exists.
Coding Errors to Avoid
- ❌ Don’t assign E87.1 without lab confirmation
- ❌ Avoid using it as secondary when it’s the main problem
- ❌ Don’t omit secondary causes like medication-induced electrolyte imbalance
Bullet Points: High-Yield Tips for Coders
- Review labs before coding
- Collaborate with clinicians to confirm causes
- Always use latest ICD-10 update
- Document symptoms like confusion or nausea
- Use modifiers only if needed by payer
Real-Life Case: Hyponatremia in ER Setting
Patient: Male, 73, brought in after fainting. Labs show sodium at 119 mmol/L. History of diuretic use.
Treatment: IV saline + stopping medication
Codes:
- E87.1: Hyponatremia
- I95.1: Orthostatic hypotension
- I10: Hypertension
This approach helped the hospital secure full reimbursement with zero payer rejections.
Acute vs. Chronic Hyponatremia
| Type | Characteristics | Coding Notes |
|---|---|---|
| Acute | <48 hours onset, neurological symptoms | Still E87.1, note in file |
| Chronic | Gradual, mild symptoms over time | E87.1 with note on duration |
Use clinical judgment or provider notes to guide documentation.
How Doctors Can Improve ICD-10 Accuracy
Clinical Documentation Tips
- Be specific: is it acute or chronic?
- Link lab results to clinical signs
- Mention comorbidities in your assessment
- Use SMART notes (Specific, Measurable, Actionable, Relevant, Timely)
Example: “Patient presents with fatigue, labs show Na+ = 128 mmol/L. Suspect hyponatremia secondary to hydrochlorothiazide.”
How to Prevent Hyponatremia in Clinical Practice
Actionable Steps for Providers
- Review medications for electrolyte side effects
- Monitor sodium regularly in elderly and renal patients
- Educate patients on hydration and salt intake
- Use IV fluids only when medically indicated
Table: ICD-10 Comparisons for Electrolyte Disorders
| Code | Condition | Clinical Marker |
|---|---|---|
| E87.1 | Hyponatremia | Na+ <135 mmol/L |
| E87.0 | Hypernatremia | Na+ >145 mmol/L |
| E86.0 | Dehydration | ↑BUN, dry mucosa |
| E83.42 | Hypomagnesemia | Mg <1.5 mg/dL |
This chart helps distinguish overlapping conditions that often coexist with hyponatremia.
FAQ: Hyponatremia ICD 10 Code
What is the ICD-10 code for hyponatremia?
E87.1 is the official code used for low serum sodium levels under 135 mmol/L.
Can E87.1 be coded as a secondary diagnosis?
Yes, but only when another condition like CHF is the primary diagnosis.
What labs support this code?
A sodium blood test showing levels below 135 mmol/L is required for validation.
Do I need to specify acute or chronic?
No separate code exists, but documentation should clarify the duration.
Is E87.1 reimbursable?
Absolutely, if supported by lab and clinical documentation. It’s a common billable diagnosis.
Final Thoughts and Actionable CTA
Hyponatremia is a silent threat. But when diagnosed and coded correctly, it becomes a manageable clinical situation. Using the correct hyponatremia ICD 10 code (E87.1) doesn’t just improve charting—it protects the patient and optimizes your practice’s billing cycle.
Next steps for you:
- ✅ Review your EMRs for sodium coding accuracy
- ✅ Educate staff on proper electrolyte coding
- ✅ Use this article as a reference in your practice or clinic
Need help training your medical coders or EHR team?
Contact a certified medical coding specialist or consider hosting a documentation training session using this article as a template.
