E87.6: Hypokalemia

The ICD-10-CM code for hypokalemia, a documented serum potassium below 3.5 mEq/L, whether it stands alone or complicates an underlying condition.

Billable

FY2027

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At a glance

Code Family

E87: Other disorders of fluid, electrolyte and acid-base balance.

Condition

Hypokalemia

Billable

Yes. E87.6 is a valid code with no child codes and needs no further character.

HCC Mapping (v28)

No HCC mapping. E87.6 does not map to any CMS-HCC v28 category.

Family Specificity

A single billable code covering every presentation of low serum potassium, from mild at 3.0 to 3.5 mEq/L through severe below 2.5 mEq/L, with no severity subclassification in ICD-10-CM FY2027.

Effective Date

Valid in the FY2026 code set and unchanged in the FY2027 update.

Which E87 code do I assign?

The E87 family splits on which derangement of fluid, electrolyte or acid-base balance the record names, not on how severe that derangement is. E87.6 applies when the documentation names a low serum potassium, below 3.5 mEq/L.

When documentation says…

Code

Potassium 3.1, potassium chloride started

E87.6

Hypokalemia, a serum potassium below 3.5 mEq/L. The note must carry the diagnosis as confirmed and show the provider addressed it, through supplementation, repeat laboratory orders or a diuretic dose change.

Potassium 5.9, elevated

E87.5

Hyperkalemia. An elevated potassium is the opposite finding and takes E87.5, never E87.6.

Sodium 128, hyponatremia

E87.1

Hypo-osmolality and hyponatremia. Low sodium is a separate abnormality with its own code.

Hypokalemia from chronic furosemide

T50.1X5A

Adverse effect of loop [high-ceiling] diuretics, initial encounter. Guideline I.C.19.e.5.a sequences the nature of the adverse effect first. Report E87.6 first and T50.1X5A after it.

Refractory hypokalemia, primary hyperaldosteronism

E26.01

Conn's syndrome, a documented cause of refractory hypokalemia. Code the underlying cause where the record establishes it, with E87.6 reported alongside.

Dehydration with electrolyte imbalance

E86.0

Dehydration. Use E86.0 when dehydration is the documented condition and no more specific electrolyte code applies.

Tabular notes

EXCLUDES1

E87.6 itself carries no code level Excludes1 restriction. The parent category E87 carries Excludes1 notes that apply to every E87 code: diabetes insipidus (E23.2), electrolyte imbalance associated with hyperemesis gravidarum (O21.1), electrolyte imbalance following ectopic or molar pregnancy (O08.5), familial periodic paralysis (G72.3), and metabolic acidemia in newborn, unspecified (P19.9). Do not assign E87.6 when one of those excluded conditions fully explains the electrolyte disorder.

FY2027: EFFECTIVE 1 OCTOBER 2026

The FY2027 codes addenda add and delete no codes in category E87. The only FY2027 tabular change in the category rewords the Code first note at E87.22, chronic metabolic acidosis. E87.6 is unchanged in the FY2027 update. No codes were added to or deleted from category E87 in FY2026.

Operational & financial impact

Why specificity matters beyond the chart: risk adjustment, DRG assignment and denial exposure all follow from which code is selected.

CMS-HCC v28 (PY2024+)

E87.6 does not map to any Hierarchical Condition Category under CMS-HCC Model Version 28.

CMS-HCC v28 is fully operative at 100 percent weight for Medicare Advantage payment year 2026.

Hypokalemia and related electrolyte disorders are not risk adjusting conditions under the current CMS model.

SEQUENCING UNDER THE FY2027 GUIDELINES

Sequence E87.6 as the principal or primary diagnosis when hypokalemia is the reason for the encounter. On an inpatient record it is the principal diagnosis when it is the condition established after study to be chiefly responsible for the admission (Section II).

When hypokalemia is an adverse effect of a correctly prescribed and properly administered drug, Guideline I.C.19.e.5.a sequences E87.6 first. The adverse effect code from T36–T50, with a fifth or sixth character 5, follows it.

When hypokalemia is a secondary finding managed alongside another primary condition, report E87.6 as an additional code.

MEDICARE AND COMMERCIAL PAYERS

There is no National Coverage Determination specific to E87.6.

The code supports medical necessity for electrolyte monitoring, intravenous potassium replacement and the related workup.

E87.6 generates no HCC risk adjustment weight under CMS-HCC v28.

WHERE SPECIFICITY IS LOST

E87.6 carries no severity subclassification. A potassium of 3.4 mEq/L and a potassium below 2.5 mEq/L reach the same code. Severity lives in the narrative and the laboratory value rather than in the code.

Coding E87.6 from a laboratory result alone, with no documentation that the provider addressed the disturbance, leaves the diagnosis unsupported on review.

Omitting the adverse effect code when a correctly administered medication caused the hypokalemia understates the encounter.

Documentation checklist to support E87.6

Chart elements that support code selection and reduce specificity-driven denials.

Provider documentation of hypokalemia as a confirmed diagnosis.

A serum potassium laboratory value below 3.5 mEq/L supporting that diagnosis.

Clinical notation acknowledging and addressing the electrolyte disturbance, such as potassium supplementation, a repeat laboratory order or a diuretic dose adjustment.

The documented etiology where one is established, such as diuretic use, vomiting, diarrhea, hyperaldosteronism, refeeding syndrome or chronic kidney disease.

Where the cause is an adverse effect of a correctly administered medication, the drug detail needed to support the T36–T50 code that follows E87.6.

For outpatient encounters, clinical acknowledgment at the encounter itself rather than a laboratory report on its own.

For inpatient stays, evidence that the hypokalemia affected patient care through monitoring, treatment or extended length of stay, as UHDDS requires of an additional diagnosis.

Confirmation that no Excludes1 condition at category E87 fully explains the electrolyte disorder.

FAQ

Is E87.6 a billable code?

Yes. E87.6 is a valid billable code. It has no child codes. No further character is required.

When do I use E87.6 instead of E87.5?

Use E87.6 for hypokalemia, a serum potassium below 3.5 mEq/L. Use E87.5 for hyperkalemia, an elevated potassium. The two are opposite findings and are never interchangeable.

Does E87.6 map to an HCC under CMS-HCC v28?

No. E87.6 does not map to any Hierarchical Condition Category in CMS-HCC Model Version 28, which is fully operative at 100 percent weight for Medicare Advantage payment year 2026. Hypokalemia and related electrolyte disorders carry no risk adjustment weight under the current model.

Can I code E87.6 from the laboratory value alone?

No. The provider must document hypokalemia as a diagnosis and address it at the encounter, through potassium supplementation, repeat labs or a diuretic dose change. A potassium result on a laboratory report, without that clinical acknowledgment, does not support the code.

How do I sequence E87.6 when a diuretic caused the hypokalemia?

Sequence E87.6 first as the nature of the adverse effect. The adverse effect code from T36–T50, with a fifth or sixth character 5, follows it (Guideline I.C.19.e.5.a). For a loop diuretic at an initial encounter the adverse effect code is T50.1X5A.

Does E87.6 work differently for inpatient and outpatient encounters?

The documentation threshold differs. On the outpatient side, code E87.6 when the provider documents and addresses the hypokalemia at that encounter. On the inpatient side, report it as an additional diagnosis under UHDDS guidelines when it affects patient care through monitoring, treatment or extended stay.

What changed for E87.6 in FY2027?

E87.6 is unchanged in the FY2027 update, effective 1 October 2026. The FY2027 update adds and deletes no codes in category E87. Its only tabular change in the category rewords the Code first note at E87.22, chronic metabolic acidosis. No codes were added to or deleted from category E87 in FY2026.

Which Excludes1 conditions block E87.6?

Category E87 carries Excludes1 notes for diabetes insipidus (E23.2), electrolyte imbalance associated with hyperemesis gravidarum (O21.1), electrolyte imbalance following ectopic or molar pregnancy (O08.5), familial periodic paralysis (G72.3), and metabolic acidemia in newborn, unspecified (P19.9). Do not assign E87.6 when one of those conditions fully explains the electrolyte disorder.

Related codes

Codes in the same family as E87.6. Only codes with a published page render as links.

Sibling codes in the E87 family

E87.0: Hyperosmolality and hypernatremia.
E87.1: Hypo-osmolality and hyponatremia.
E87.2-: Acidosis, a subcategory that requires a fifth character.
E87.3: Alkalosis.
E87.4: Mixed disorder of acid-base balance.
E87.5: Hyperkalemia.
E87.7-: Fluid overload, a subcategory that requires a fifth character.
E87.8: Other disorders of electrolyte and fluid balance, not elsewhere classified.

Additional codes to consider

Codes outside the E87 family considered alongside E87.6.

Companion: code alongside when documented

T50.1X5A: Adverse effect of loop [high-ceiling] diuretics, initial encounter, sequenced after E87.6 when a correctly administered loop diuretic caused the hypokalemia (Guideline I.C.19.e.5.a).

Consider instead

E86.0: Dehydration, where dehydration with electrolyte imbalance is the documented condition and no more specific electrolyte code applies.
E83.39: Other disorders of phosphorus metabolism, where the documented abnormality is phosphorus rather than potassium.
E23.2: Diabetes insipidus, an Excludes1 condition at category E87.
G72.3: Periodic paralysis, which covers familial periodic paralysis and is an Excludes1 condition at category E87.
O21.1: Hyperemesis gravidarum with metabolic disturbance, an Excludes1 condition at category E87.
O08.5: Metabolic disorders following an ectopic and molar pregnancy, an Excludes1 condition at category E87.

Sources

All claims on this page derive from government and professional-standards sources.

National Center for Health Statistics. (2026). International classification of diseases, tenth revision, clinical modification (ICD-10-CM) FY2027 files. https://www.cdc.gov/nchs/icd/icd-10-cm/files.html
Centers for Medicare & Medicaid Services and National Center for Health Statistics. (2026). ICD-10-CM official guidelines for coding and reporting FY2027. https://ftp.cdc.gov/pub/Health_Statistics/NCHS/Publications/ICD10CM/2027/ICD-10-CM-October-1-2026-FY27-Guidelines.pdf
Centers for Medicare & Medicaid Services. (2025). 2026 model software/ICD-10 mappings. https://www.cms.gov/medicare/payment/medicare-advantage-rates-statistics/risk-adjustment/2026-model-software-icd-10-mappings
Centers for Medicare & Medicaid Services. (2026). MS-DRG classifications and software, version 44. https://www.cms.gov/medicare/payment/prospective-payment-systems/acute-inpatient-pps/ms-drg-classifications-and-software