What is ICD-10 code E88.40?

E88.40 is the ICD-10-CM diagnosis code for Mitochondrial metabolism disorder, unspecified. A disorder affecting how the body's mitochondria (the energy-producing parts of cells) process and use energy, but the specific type is not identified. It belongs to the ICD-10-CM chapter for endocrine, nutritional and metabolic diseases (e00-e89). E88.40 is a billable code, meaning it can be reported on a claim as a primary or secondary diagnosis when supported by documentation. E88.40 is part of the FY2026 ICD-10-CM code set published by the CMS National Center for Health Statistics and used on Medicare, Medicaid, and commercial claims in the United States.

Yes. E88.40 is a billable ICD-10-CM code that can be reported on professional and institutional claims as a primary or secondary diagnosis when the provider documentation supports the specific condition described. Billable codes in ICD-10-CM are coded to the highest level of specificity available for the documented diagnosis. E88.40 is current for fiscal year 2026 and remains in the active CMS ICD-10-CM code set published by the National Center for Health Statistics.

Which HCC does E88.40 map to under V28?

E88.40 has no payable CMS-HCC V28 mapping in the final FY2026 CMS file.

What RAF reference is published for E88.40?

E88.40 has no V28 reference coefficient because the final FY2026 source verifies no payable V28 mapping.

What is the V28 vs V24 difference for E88.40?

E88.40 has verified no payable V28 mapping in the final FY2026 source. Select a historical effective period before making any V24 comparison.

What documentation supports E88.40?

Use this code only when the specific mitochondrial disorder cannot be determined; if a more specific mitochondrial condition is identified, use the appropriate subcategory (E88.41-E88.49) This is an unspecified code and should be avoided when possible in favor of more specific diagnoses E88.40 is not a CMS-HCC V28 payment code in the verified current source, so MEAT is not the payment hook. Documentation still has to support the diagnosis if you report it.

2026 ICD-10-CM E88.40: Mitochondrial metabolism disorder

E88.40 is not a CMS-HCC payment code. MEAT criteria · RAF Calculator · HCC Buddy coding tools

ICD-10-CM Code View

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Code lookupE88.40

Effective periodFY2026 Apr Update (Apr 1-Sep 30)

FY 2026 Apr update / Endocrine, nutritional and metabolic diseases (E00-E89) / Metabolic disorders (E70-E88)

E88.40

Billable / SpecificICD-10-CMOfficial ICD-10-CMCodebook guidance

Mitochondrial metabolism disorder, unspecified

A disorder affecting how the body's mitochondria (the energy-producing parts of cells) process and use energy, but the specific type is not identified.

Buddy Insight

Unspecified mitochondrial metabolism disorders represent a broad category of genetic conditions affecting cellular energy production.

Overview Risk Models Code Book Documentation Audit Notes Edition comparison

CMS-HCC V28

N/A

—

Not risk-adjusted for this model/period.

Not mapped

CMS-HCC V24

Historical

Not used for standard CY2026 Medicare Advantage payment. Select a historical period to review V24.

Not used for CY2026 payment

ACA/HHS

N/A

—

Not risk-adjusted for this model/period.

Not mapped

ESRD/PACE

N/A

—

Not risk-adjusted for this model/period.

Not mapped

RXHCC

Mapped

HCC 43

Pituitary, Adrenal Gland, and...

Code-level coefficient reference

Code Book Path

Official

E88Other and unspecified metabolic disorders E88.4Mitochondrial metabolism disorders E88.40Mitochondrial metabolism disorder, unspecified

Inclusion Terms

Official

No inclusion terms are included in this display for E88.40. Check the code and parent instructions in the Code Book.

Excludes 2

Official

Ehlers-Danlos syndromes (Q79.6-)Inherited from E70-E88

Related Codes

Official

E88.41MELAS syndrome E88.42MERRF syndrome E88.43Disorders of mitochondrial tRNA synthetases E88.49Other mitochondrial metabolism disorders

Includes

Official

No Includes notes are included in this display for E88.40. Check the code and parent instructions in the Code Book.

Excludes 1

Official

transitory endocrine and metabolic disorders specific to newborn (P70-P74)Inherited from E00-E89, E70-E88, E88, E88.4
androgen insensitivity syndrome (E34.5-)Inherited from E00-E89, E70-E88, E88, E88.4
congenital adrenal hyperplasia (E25.0)Inherited from E00-E89, E70-E88, E88, E88.4
hemolytic anemias attributable to enzyme disorders (D55.-)Inherited from E00-E89, E70-E88, E88, E88.4
Marfan syndrome (Q87.4-)Inherited from E00-E89, E70-E88, E88, E88.4
5-alpha-reductase deficiency (E29.1)Inherited from E00-E89, E70-E88, E88, E88.4
histiocytosis X (chronic) (C96.6)Inherited from E00-E89, E70-E88, E88, E88.4
disorders of pyruvate metabolism (E74.4)Inherited from E00-E89, E70-E88, E88, E88.4
Kearns-Sayre syndrome (H49.81)Inherited from E00-E89, E70-E88, E88, E88.4
Leber's disease (H47.22)Inherited from E00-E89, E70-E88, E88, E88.4
Leigh's encephalopathy (G31.82)Inherited from E00-E89, E70-E88, E88, E88.4
Mitochondrial myopathy, NEC (G71.3)Inherited from E00-E89, E70-E88, E88, E88.4
Reye's syndrome (G93.7)Inherited from E00-E89, E70-E88, E88, E88.4

Code First

Official

No Code First sequencing instructions are included in this display for E88.40. Check the code and parent instructions in the Code Book.

Use Additional

Official

codes for associated conditionsInherited from E88

Code Also

Official

No Code Also instructions are included in this display for E88.40. Check the code and parent instructions in the Code Book.

Buddy Documentation Tip

HCC Buddy guidance

Diagnosis of a mitochondrial disorder by the treating provider

Clinical manifestations documented (myopathy, encephalopathy, lactic acidosis, seizures)

Laboratory evidence (elevated lactate, mitochondrial DNA studies, muscle biopsy)

Genetic testing results if available

MEAT Support

HCC Buddy guidance

Diagnosis of a mitochondrial disorder by the treating provider

Clinical manifestations documented (myopathy, encephalopathy, lactic acidosis, seizures)

Laboratory evidence (elevated lactate, mitochondrial DNA studies, muscle biopsy)

Genetic testing results if available

Audit Caution

HCC Buddy guidance

Using unspecified when MELAS, MERRF, or another named syndrome is documented

Not reviewing genetics notes for specific mitochondrial DNA mutation identification

Confusing mitochondrial myopathy (G71.3) with broader mitochondrial metabolic disorder

Failing to code multi-system manifestations separately (seizures, cardiomyopathy, diabetes)

Common Mistakes

HCC Buddy guidance

E88.41 — MELAS syndrome: specific mitochondrial disorder with stroke-like episodes; use when diagnosed

E88.42 — MERRF syndrome: specific mitochondrial disorder with myoclonus epilepsy; use when diagnosed

E88.49 — Other mitochondrial metabolism disorders: use for named syndromes without specific codes

G71.3 — Mitochondrial myopathy, not elsewhere classified: when myopathy is the primary manifestation

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 E88.40 an HCC code?

E88.40 is not in the CMS-HCC V28 or V24 community payment model. E88.40 has a separate mapping under the CMS-HCC ESRD model (HCC 23 (Other Significant Endocrine and Metabolic Disorders)) and the Part D RxHCC model (HCC 43 (Pituitary, Adrenal Gland, and Other Endocrine and Metabolic Disorders)); the applicable result needs member context. E88.40 also appears in the HHS-HCC commercial risk model (HCC 028 (HHS-HCC 028 child, RAF varies by metal level)), where the result depends on member context and is not a Medicare Advantage payment mapping.

Code: E88.40
Description: Mitochondrial metabolism disorder, unspecified
HCC (V28): No CMS-HCC V28 mapping
RAF reference coefficient: —
Billable: Yes
Payment year: 2026

HCC Category Mapping

RxHCCHCC 43, Pituitary, Adrenal Gland, and Other Endocrine and Metabolic Disorders

Not separately weighted

These are source-labeled model coefficients, not member totals. A category may still be removed by hierarchy or model cleanup rules. Weights are not directly comparable across models: CMS-HCC V28 and V24 use Community, Non-Dual, Aged; ESRD uses the dialysis continuing-enrollee model; RxHCC is the Part D continuing-enrollee, non-low-income, aged weight (a larger scale than CMS-HCC). ACA/HHS has no single weight — it varies by metal level. Actual per-patient RAF contribution depends on member context, hierarchy and cleanup rules, interactions, and the model year used by the payer. V28 is the CMS-HCC model phased in over payment years 2024–2026; V24 remains available for historical review.

Work E88.40 in the Code Book — tabular path, V28 RAF reference, and MEAT checklist →

MEAT review for E88.40

For E88.40, confirm that the documentation supports the diagnosis and meets the applicable coding, encounter, program and payer requirements. MEAT (Monitor, Evaluate, Assess, or Treat) is a review mnemonic, not a universal CMS coding rule.

MMonitor: signs, symptoms, disease progression, or lab trending documented in the note
EEvaluate: test results, medication response, or physical findings reviewed by the provider
AAssess: explicit mention in the assessment or plan with acknowledgment of status
TTreat: medication, referral, procedure, therapy, or counseling tied to the diagnosis

Coder workflow notes

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What This Code Means

E88.40 is the ICD-10-CM diagnosis code for mitochondrial metabolism disorder, unspecified. A disorder affecting how the body's mitochondria (the energy-producing parts of cells) process and use energy, but the specific type is not identified. E88.40 sits in the ICD-10-CM chapter for endocrine, nutritional and metabolic diseases (e00-e89), within the section covering metabolic disorders (e70-e88).

E88.40 has no mapping under the CMS-HCC V28 or V24 community payment models. E88.40 has a separate mapping under the CMS-HCC ESRD model (HCC 23 (Other Significant Endocrine and Metabolic Disorders)) and the Part D RxHCC model (HCC 43 (Pituitary, Adrenal Gland, and Other Endocrine and Metabolic Disorders)); the applicable result needs member context. E88.40 also appears in the HHS-HCC commercial risk model (HCC 028 (HHS-HCC 028 child, RAF varies by metal level)), where the result depends on member context and is not a Medicare Advantage payment mapping. Do not assign V28 risk adjustment value from this page; verify the applicable model and payment year before using this code for risk adjustment.

Use this code only when the specific mitochondrial disorder cannot be determined; if a more specific mitochondrial condition is identified, use the appropriate subcategory (E88.41-E88.49).

HCC Buddy maintains structured V28 and V24 mapping, source-labeled coefficient references, and MEAT documentation criteria for E88.40 sourced directly from the CMS-HCC risk adjustment model files and the CMS ICD-10-CM code set.

Coding Tips

•Use this code only when the specific mitochondrial disorder cannot be determined; if a more specific mitochondrial condition is identified, use the appropriate subcategory (E88.41-E88.49)
•This is an unspecified code and should be avoided when possible in favor of more specific diagnoses

Clinical Significance

Unspecified mitochondrial metabolism disorders represent a broad category of genetic conditions affecting cellular energy production. These disorders can cause multi-system dysfunction including neurological, muscular, cardiac, and metabolic complications. Specificity should be pursued, as named syndromes like MELAS and MERRF have dedicated codes.

Documentation Requirements

✓Diagnosis of a mitochondrial disorder by the treating provider
✓Clinical manifestations documented (myopathy, encephalopathy, lactic acidosis, seizures)
✓Laboratory evidence (elevated lactate, mitochondrial DNA studies, muscle biopsy)
✓Genetic testing results if available
✓Affected organ systems and functional status
✓Reason a more specific mitochondrial syndrome code cannot be assigned

Commonly Confused Codes

•E88.41: MELAS syndrome: specific mitochondrial disorder with stroke-like episodes; use when diagnosed
•E88.42: MERRF syndrome: specific mitochondrial disorder with myoclonus epilepsy; use when diagnosed
•E88.49: Other mitochondrial metabolism disorders: use for named syndromes without specific codes
•G71.3: Mitochondrial myopathy, not elsewhere classified: when myopathy is the primary manifestation