E87.1 ICD-10-CM Code: Hypo-osmolality and hyponatremia
HCC Buddy Code Card
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FY 2026 Apr update / Endocrine, nutritional and metabolic diseases (E00-E89) / Metabolic disorders (E70-E88)
E87.1
Billable / SpecificICD-10-CMOfficial ICD-10-CMCodebook guidanceHypo-osmolality and hyponatremia
A condition where the blood has too much water relative to salt (sodium), causing cells to swell and potentially leading to confusion, seizures, or brain swelling.
CMS-HCC V28
N/A—
Not mapped
CMS-HCC V24
N/A—
Not mapped
ACA/HHS
N/A—
Not mapped
ESRD/PACE
N/A—
Not mapped
RXHCC
N/A—
Not mapped
Code Book Path
Inclusion Terms
Official- Sodium [Na] deficiency
Excludes 2
OfficialICD-10-CM does not list Excludes 2 notes for E87.1 in this effective period.
Related Child Codes
Includes
OfficialICD-10-CM does not list Includes notes for E87.1 in this effective period.
Excludes 1
Official- syndrome of inappropriate secretion of antidiuretic hormone (E22.2)
Code First
OfficialICD-10-CM does not list Code First sequencing instructions for E87.1 in this effective period.
Use Additional
OfficialICD-10-CM does not list Use Additional Code instructions for E87.1 in this effective period.
Code Also
OfficialICD-10-CM does not list Code Also instructions for E87.1 in this effective period.
Buddy Documentation Tip
Current with CMS: FY2026 ICD-10-CM Apr 1 update (effective Apr 1 – Sep 30, 2026) · CMS-HCC V28, 100% phased in for payment year 2026. FY2027 code set already staged for October 1, 2026. How HCC Buddy stays current →
Is E87.1 an HCC code?
No. E87.1 is a billable ICD-10-CM code but does not map to any HCC category in V28, V24, ESRD, or RxHCC.
- Code
- E87.1
- Description
- Hypo-osmolality and hyponatremia
- HCC (V28)
- No CMS-HCC V28 mapping
- RAF
- —
- Billable
- Yes
- Payment year
- 2026
Coder workflow notes
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This code does not map to an HCC category in any model (V28, V24, ESRD, RxHCC).
What This Code Means
E87.1 is the ICD-10-CM diagnosis code for hypo-osmolality and hyponatremia. A condition where the blood has too much water relative to salt (sodium), causing cells to swell and potentially leading to confusion, seizures, or brain swelling. E87.1 sits in the ICD-10-CM chapter for endocrine, nutritional and metabolic diseases (e00-e89), within the section covering metabolic disorders (e70-e88).
E87.1 is a billable ICD-10-CM code but does not map to a payment HCC under the CMS-HCC V28, V24, ESRD, or RxHCC risk adjustment models. It can be reported on Medicare Advantage encounter data submissions but it does not contribute to a beneficiary's RAF score and therefore does not affect risk-adjusted payments to the plan.
Distinguish between acute and chronic hyponatremia, as treatment approaches differ significantly.
HCC Buddy maintains structured V28 and V24 mapping, RAF weights, and MEAT documentation criteria for E87.1 sourced directly from the CMS-HCC risk adjustment model files and the CMS ICD-10-CM code set.
Coding Tips
- •Distinguish between acute and chronic hyponatremia, as treatment approaches differ significantly
- •Document the underlying cause such as SIADH, excessive water intake, or diuretic use
Excludes 1, Do NOT code together
- syndrome of inappropriate secretion of antidiuretic hormone (E22.2)