What is ICD-10 code E70.0?

E70.0 is the ICD-10-CM diagnosis code for Classical phenylketonuria. A rare inherited metabolic disorder where the body cannot properly break down the amino acid phenylalanine, leading to intellectual disability if untreated. It belongs to the ICD-10-CM chapter for endocrine, nutritional and metabolic diseases (e00-e89). E70.0 is a billable code, meaning it can be reported on a claim as a primary or secondary diagnosis when supported by documentation. E70.0 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. E70.0 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. E70.0 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 E70.0 map to under V28?

E70.0 does not map to a CMS-HCC V28 payment category. Check the current CMS-HCC V28 model file for payment year 2026 rather than an older V24 tip sheet.

What does E70.0 pay in RAF?

E70.0 has no separately stated V28 community RAF weight. If it is not a V28 payment HCC, it adds nothing to a community RAF score.

What is the V28 vs V24 difference for E70.0?

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. E70.0 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.

2026 ICD-10-CM E70.0: Classical phenylketonuria

E70.0 is not a CMS-HCC payment code. MEAT criteria · RAF calculator · free HCC coding tools

ICD-10-CM Code View

HCC Buddy Code Card

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Code lookupE70.0Effective periodFY2026 Apr Update (Apr 1-Sep 30)

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

E70.0

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

Classical phenylketonuria

A rare inherited metabolic disorder where the body cannot properly break down the amino acid phenylalanine, leading to intellectual disability if untreated.

Buddy Insight

Classical phenylketonuria is a serious autosomal recessive inborn error of metabolism caused by deficiency of phenylalanine hydroxylase, preventing conversion of phenylalanine to tyrosine.

CMS-HCC V28

N/A

—

Not risk-adjusted for this model/period.

Not mapped

CMS-HCC V24

Mapped

HCC 23

Other Significant Endocrine a...

RAF 0.194

ACA/HHS

Mapped

HCC 28

HHS-HCC 28

Varies by metal level

ESRD/PACE

Mapped

HCC 23

Other Significant Endocrine a...

RAF 0.036

RXHCC

Mapped

HCC 42

Endocrine Disorders and Metab...

RAF 2.110

Code Book Path

Official

E70Disorders of aromatic amino-acid metabolism

E70.0Classical phenylketonuria

Inclusion Terms

Official

ICD-10-CM does not list inclusion terms for E70.0 in this effective period.

Excludes 2

Official

ICD-10-CM does not list Excludes 2 notes for E70.0 in this effective period.

Related Child Codes

Official

E70.1Other hyperphenylalaninemias

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 E70.0 in this effective period.

Excludes 1

Official

ICD-10-CM does not list Excludes 1 notes for E70.0 in this effective period.

Code First

Official

ICD-10-CM does not list Code First sequencing instructions for E70.0 in this effective period.

Use Additional

Official

ICD-10-CM does not list Use Additional Code instructions for E70.0 in this effective period.

Code Also

Official

ICD-10-CM does not list Code Also instructions for E70.0 in this effective period.

Buddy Documentation Tip

HCC Buddy guidance

Documentation should include the confirmed diagnosis from newborn screening or diagnostic testing showing elevated phenylalanine levels (typically above 20 mg/dL), current phenylalanine blood levels and target ranges, dietary management including phenylalanine-restricted diet and medical formula use, and any neurological or developmental complications.

For maternal phenylketonuria, pregnancy status and fetal effects should be documented.

MEAT Support

HCC Buddy guidance

For maternal phenylketonuria, pregnancy status and fetal effects should be documented.

Audit Caution

HCC Buddy guidance

Do not confuse classical phenylketonuria (E70.0) with mild or benign hyperphenylalaninemia (E70.1), which has a different clinical course and management approach.

Ensure the provider documents classical phenylketonuria specifically.

Maternal phenylketonuria syndrome in pregnancy requires additional obstetric codes.

Do not use this code for transient neonatal hyperphenylalaninemia, which resolves spontaneously.

Common Mistakes

HCC Buddy guidance

E70.1 (Other hyperphenylalaninemias) captures milder forms with lower phenylalanine levels that may not require as strict dietary management.

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

E70.9 (Disorder of aromatic amino-acid metabolism, unspecified) should not be used when classical phenylketonuria is documented.

P74.31 (Neonatal hyperphenylalanemia) is for newborns with elevated levels before definitive diagnosis.

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 E70.0 an HCC code?

Yes. E70.0 maps to Other Significant Endocrine and Metabolic Disorders under the V24 model but is not retained in V28.

Code: E70.0
Description: Classical phenylketonuria
HCC (V28): No CMS-HCC V28 mapping
RAF: —
Billable: Yes
Payment year: 2026

HCC Category Mapping

V24HCC 23, Other Significant Endocrine and Metabolic Disorders

0.194

ESRDHCC 23, Other Significant Endocrine and Metabolic Disorders

0.036

RxHCCHCC 42, Endocrine Disorders and Metabolic Conditions

2.110

Each model's RAF is its CMS base weight for that model's standard population, so 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 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 E70.0 in the Code Book — tabular path, V28 RAF, and MEAT checklist →

MEAT Criteria for E70.0

For E70.0 to 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 E70.0 during that encounter, not just copy-forwarded from a problem list.

Coder workflow notes

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What This Code Means

E70.0 is the ICD-10-CM diagnosis code for classical phenylketonuria. A rare inherited metabolic disorder where the body cannot properly break down the amino acid phenylalanine, leading to intellectual disability if untreated. E70.0 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, E70.0 maps to Other Significant Endocrine and Metabolic Disorders (HCC 23) with a community, non-dual, aged base RAF weight of 0.194. 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.

This is a congenital condition; verify if the patient has been diagnosed through newborn screening. Because E70.0 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 E70.0 sourced directly from the CMS-HCC risk adjustment model files and the CMS ICD-10-CM code set.

Coding Tips

•This is a congenital condition; verify if the patient has been diagnosed through newborn screening
•Document whether the patient is on a phenylalanine-restricted diet for management

Clinical Significance

Classical phenylketonuria is a serious autosomal recessive inborn error of metabolism caused by deficiency of phenylalanine hydroxylase, preventing conversion of phenylalanine to tyrosine. Without lifelong dietary restriction of phenylalanine, this condition leads to severe intellectual disability, seizures, behavioral problems, and eczema. Newborn screening has dramatically improved outcomes through early dietary intervention.

Documentation Requirements

✓Documentation should include the confirmed diagnosis from newborn screening or diagnostic testing showing elevated phenylalanine levels (typically above 20 mg/dL), current phenylalanine blood levels and target ranges, dietary management including phenylalanine-restricted diet and medical formula use, and any neurological or developmental complications.
✓For maternal phenylketonuria, pregnancy status and fetal effects should be documented.

Commonly Confused Codes

•E70.1 (Other hyperphenylalaninemias) captures milder forms with lower phenylalanine levels that may not require as strict dietary management.
•E70.20-E70.29 (Disorders of tyrosine metabolism) involve a different amino acid pathway.
•E70.9 (Disorder of aromatic amino-acid metabolism, unspecified) should not be used when classical phenylketonuria is documented.
•P74.31 (Neonatal hyperphenylalanemia) is for newborns with elevated levels before definitive diagnosis.