What is ICD-10 code E70.1?

E70.1 is the ICD-10-CM diagnosis code for Other hyperphenylalaninemias. A group of inherited metabolic conditions where phenylalanine levels are elevated in the blood but not as severe as classical phenylketonuria. It belongs to the ICD-10-CM chapter for endocrine, nutritional and metabolic diseases (e00-e89). E70.1 is a billable code, meaning it can be reported on a claim as a primary or secondary diagnosis when supported by documentation. E70.1 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. E70.1 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. E70.1 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.

What is the V28 vs V24 difference for E70.1?

CMS phased in the V28 risk adjustment model over payment years 2024 (33%), 2025 (67%), and 2026 (100%), replacing V24. V28 consolidates HCC categories, removes some lower-acuity conditions, and recalibrates RAF weights across the entire model. E70.1 was a payment HCC under V24 (Other Significant Endocrine and Metabolic Disorders) but the V28 recalibration removed it from the risk adjustment model. Both models can still appear in legacy data and in payer-specific lookback periods.

What should coders know when reporting E70.1?

Distinguish between classical PKU (E70.0) and other hyperphenylalaninemias (E70.1) Document the specific type of hyperphenylalaninemia when available (benign, mild, or variant forms) Because E70.1 maps to a payment HCC, the documentation must also satisfy MEAT criteria (Monitor, Evaluate, Assess, or Treat) for the encounter to count toward the patient's risk adjustment score.

E70.1: Other hyperphenylalaninemias — ICD-10 | Other Significant Endocrine and Metabolic Disorders

ICD-10-CM Code View

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Code lookupE70.1Effective periodFY2026 Apr Update (Apr 1-Sep 30)

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

E70.1

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

Other hyperphenylalaninemias

A group of inherited metabolic conditions where phenylalanine levels are elevated in the blood but not as severe as classical phenylketonuria.

Buddy Insight

CMS-HCC V28

Not risk-adjusted for this model/period.

RAF 0

CMS-HCC V24

Mapped

HCC 23

Other Significant Endocrine a...

RAF 0.230

ACA/HHS

Not risk-adjusted for this model/period.

RAF 0

ESRD/PACE

Mapped

HCC 23

Other Significant Endocrine a...

RAF 0.0

RXHCC

Mapped

HCC 42

Endocrine Disorders and Metab...

RAF 0.0

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Code Book Path

Official

E70Disorders of aromatic amino-acid metabolism

E70.1Other hyperphenylalaninemias

Inclusion Terms

Official

ICD-10-CM does not list inclusion terms for E70.1 in this effective period.

Excludes 2

Official

ICD-10-CM does not list Excludes 2 notes for E70.1 in this effective period.

Related Child Codes

Official

E70.0Classical phenylketonuria

E70.2Disorders of tyrosine metabolism

E70.3Albinism

E70.4Disorders of histidine metabolism

E70.5Disorders of tryptophan metabolism

Includes

Official

ICD-10-CM does not list Includes notes for E70.1 in this effective period.

Excludes 1

Official

ICD-10-CM does not list Excludes 1 notes for E70.1 in this effective period.

Code First

Official

ICD-10-CM does not list Code First sequencing instructions for E70.1 in this effective period.

Use Additional

Official

ICD-10-CM does not list Use Additional Code instructions for E70.1 in this effective period.

Code Also

Official

ICD-10-CM does not list Code Also instructions for E70.1 in this effective period.

Buddy Documentation Tip

HCC Buddy guidance

Documentation should specify the type of hyperphenylalaninemia (benign, mild, variant, or biopterin-responsive), phenylalanine blood levels with target ranges, biopterin loading test results if applicable, current dietary management status, and neurological assessment.

For women of reproductive age, documentation should address maternal phenylketonuria counseling.

Distinguish clearly from classical phenylketonuria in the medical record.

MEAT Support

HCC Buddy guidance

For women of reproductive age, documentation should address maternal phenylketonuria counseling.

Distinguish clearly from classical phenylketonuria in the medical record.

Audit Caution

HCC Buddy guidance

Do not code mild hyperphenylalaninemia as classical phenylketonuria (E70.0), as the treatment and prognosis differ significantly.

Ensure the provider distinguishes between the variants of hyperphenylalaninemia.

Biopterin-responsive hyperphenylalaninemia may require supplementation rather than dietary restriction, and this distinction should be documented.

Do not assume all elevated phenylalanine levels represent the same condition.

Common Mistakes

HCC Buddy guidance

E70.0 (Classical phenylketonuria) is for the severe form with phenylalanine hydroxylase deficiency.

E70.9 (Disorder of aromatic amino-acid metabolism, unspecified) is less specific and should not be used when hyperphenylalaninemia is documented.

E70.20-E70.29 (Disorders of tyrosine metabolism) involve a downstream amino acid.

P74.31 (Neonatal hyperphenylalanemia) is a newborn-specific code for transient elevation.

Last updated: FY2026 ICD-10-CM Apr update, Apr 1, 2026 through Sep 30, 2026. CMS-HCC V28 is 100% phased in for payment year 2026.

Is E70.1 an HCC code?

Yes. E70.1 maps to Other Significant Endocrine and Metabolic Disorders under the V24 model but is not retained in V28.

HCC Category Mapping

V24HCC 23, Other Significant Endocrine and Metabolic Disorders

0.230

ESRDHCC 23, Other Significant Endocrine and Metabolic Disorders

0.000

RxHCCHCC 42, Endocrine Disorders and Metabolic Conditions

0.000

RAF weights shown are the community, non-dual, aged base weights from the CMS risk adjustment model file. Actual per-patient RAF contribution depends on member segment, interactions, and the model year used by the payer. V28 is the CMS-HCC model phased in over payment years 2024–2026; V24 remains in use during the transition and for historical data.

Work E70.1 in the Code Book — tabular path, V28 RAF, and MEAT checklist →

MEAT Criteria for E70.1

For E70.1to count as a valid HCC diagnosis in a given encounter, the provider's documentation must show MEAT: Monitor, Evaluate, Assess, or Treat. A diagnosis from a prior year does not carry forward automatically, it has to be re-documented and supported each calendar year.

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

Only one of M/E/A/T is required to support the code, but the documentation must be specific enough to show that the provider actually addressed E70.1 during that encounter, not just copy-forwarded from a problem list.

Coder workflow notes

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What This Code Means

E70.1 is the ICD-10-CM diagnosis code for other hyperphenylalaninemias. A group of inherited metabolic conditions where phenylalanine levels are elevated in the blood but not as severe as classical phenylketonuria. E70.1 sits in the ICD-10-CM chapter for endocrine, nutritional and metabolic diseases (e00-e89), within the section covering metabolic disorders (e70-e88).

Under the older CMS-HCC V24 model, E70.1 maps to Other Significant Endocrine and Metabolic Disorders (HCC 23) with a community, non-dual, aged base RAF weight of 0.230. V28 is the CMS-HCC risk adjustment model that reached 100% phase-in for payment year 2026, replacing V24 which was used during the PY2024–PY2025 transition.

Distinguish between classical PKU (E70.0) and other hyperphenylalaninemias (E70.1). Because E70.1 maps to a payment HCC, the provider's documentation must satisfy MEAT criteria (Monitor, Evaluate, Assess, or Treat) for the encounter to count toward the patient's Medicare Advantage risk adjustment score. When documentation is ambiguous, coders should issue a provider query rather than assume the highest-specificity variant.

HCC Buddy maintains structured V28 and V24 mapping, RAF weights, and MEAT documentation criteria for E70.1 sourced directly from the CMS-HCC risk adjustment model files and the CMS ICD-10-CM code set.

Coding Tips

•Distinguish between classical PKU (E70.0) and other hyperphenylalaninemias (E70.1)
•Document the specific type of hyperphenylalaninemia when available (benign, mild, or variant forms)

Clinical Significance

Other hyperphenylalaninemias include milder forms of elevated blood phenylalanine that do not reach the severity of classical phenylketonuria, such as benign hyperphenylalaninemia and biopterin cofactor deficiencies. These conditions may require less restrictive dietary management than classical phenylketonuria but still necessitate ongoing monitoring to prevent neurological complications, particularly in women of childbearing age due to maternal hyperphenylalaninemia risks.

Documentation Requirements

✓Documentation should specify the type of hyperphenylalaninemia (benign, mild, variant, or biopterin-responsive), phenylalanine blood levels with target ranges, biopterin loading test results if applicable, current dietary management status, and neurological assessment.
✓For women of reproductive age, documentation should address maternal phenylketonuria counseling.
✓Distinguish clearly from classical phenylketonuria in the medical record.

Commonly Confused Codes

•E70.0 (Classical phenylketonuria) is for the severe form with phenylalanine hydroxylase deficiency.
•E70.9 (Disorder of aromatic amino-acid metabolism, unspecified) is less specific and should not be used when hyperphenylalaninemia is documented.
•E70.20-E70.29 (Disorders of tyrosine metabolism) involve a downstream amino acid.
•P74.31 (Neonatal hyperphenylalanemia) is a newborn-specific code for transient elevation.