ICD-10 O21.0
Billable / SpecificMild hyperemesis gravidarum
About ICD-10-CM O21.0
ICD-10-CM code O21.0 represents Mild hyperemesis gravidarum. This is a billable/specific code in the Pregnancy, Childbirth, and Puerperium chapter (block O21). The 2026 edition of ICD-10-CM O21.0 became effective on October 1, 2025.
Coding Tips for O21.0
Specialist guidance from the PayerReady Medical Coding Team. Specificity warnings, HCC capture rules, sequencing notes.
Most O codes require a 7th character indicating trimester (1 = first, 2 = second, 3 = third). Some require fetus identification character. Code O09 (supervision of high-risk pregnancy) is required as a secondary code when applicable.
Inclusion Terms / Approximate Synonyms
Clinical terms and conditions classified under O21.0. Per CMS ICD-10-CM Tabular 2026.
- Hyperemesis gravidarum, mild or unspecified, starting before the end of the 20th week of gestation
Medicare LCD Coverage for O21.0
Local Coverage Determinations (LCDs) from CMS MACs that list O21.0 as a covered diagnosis.
Showing top 1. Click a CPT for full coverage scope.
Commercial Payer Coverage
Coverage policies from major commercial payers referencing O21.0.
4 Aetna
2 Cigna
1 Medicare
CPT Codes Commonly Billed with O21.0
Procedures frequently paired with this diagnosis based on PayerReady's Dx↔Px linkage data.
We don't have CPT pairings indexed for this specific code yet. Use the CPT search above to find common procedures, or check your payer's published medical policy for code-specific guidance.
Convert O21.0 to ICD-9-CM
Per CMS General Equivalence Mappings (GEMs), useful for legacy data review and historical claim analysis.
| ICD-10 | ICD-9 | Mapping Flags |
|---|---|---|
| O21.0 | 64303 | 10000 |
Flags format (5 digits): Approximate · No Map · Combination · Scenario · Choice List. Source: CMS 2017 GEMs (final version).
Codes Adjacent To O21.0
Other codes in section O20-O29 (Other maternal disorders predominantly related to pregnancy).
ICD-10 O21.0, Billing FAQ
Is ICD-10 code O21.0 billable? +
Yes, O21.0 is a billable ICD-10-CM code that can appear as a primary or secondary diagnosis on claims.
What other names or terms map to O21.0? +
ICD-10 O21.0 includes: Hyperemesis gravidarum, mild or unspecified, starting before the end of the 20th week of gestation.
What ICD-9 codes does O21.0 map to? +
Per CMS GEMs, O21.0 maps to ICD-9 codes: 64303. Useful for legacy data review and historical claim analysis.
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Reviewed by the PayerReady Medical Coding Team
Verified against the CMS 2026 code set on May 31, 2026.
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