HK Modifier: Specialized Programs for High-Risk Populations
HK is a program modifier, and its federal descriptor is broad enough that each state decides what it means in practice. Ohio's use is the most specific.
Short answer
HK is the HCPCS Level II modifier "Specialized mental health programs for high-risk populations." Ohio Medicaid uses HK as a procedure modifier for licensed practitioners providing therapeutic behavioral services group hourly or per diem (day treatment), or SUD intensive outpatient, partial hospitalization, or group counseling. Michigan retired HK on H2014 out-of-home non-vocational habilitation in favor of its own modifier, WZ.
| Modifier | HCPCS descriptor | Type |
|---|---|---|
| HK | Specialized mental health programs for high-risk populations | Program |
How Ohio uses HK
In Ohio, HK separates a licensed practitioner's work in these group-based levels of care from paraprofessional delivery of the same service:
- Therapeutic behavioral services. Group hourly or per diem, also called day treatment.
- SUD intensive outpatient. Licensed practitioners in an IOP program.
- SUD partial hospitalization. Licensed practitioners in a PHP program.
- SUD group counseling. Licensed practitioners delivering group counseling.
Michigan's change
Michigan's code sets now report out-of-home non-vocational habilitation on H2014 with its state modifier WZ, which it notes previously used HK. Several states have moved specialized-program reporting to state-defined modifiers, so check the current year's code set.
Why HK claims deny
- Licensed practitioner without HK in Ohio. Group, IOP, or PHP billed without the modifier that sets the licensed rate.
- HK on paraprofessional delivery. The rendering staff member is not a licensed practitioner.
- Retired use. HK sent where the state now expects a state-specific modifier.
Related: H0015 intensive outpatient, H2019 and H2020, all behavioral health HCPCS modifiers, and the code map in H codes in behavioral health.
Sources, read October 2026: Ohio Medicaid Behavioral Health Provider Manual, v1.28.1 (March 2026); MDHHS SFY 2027 Behavioral Health Code Charts and Provider Qualifications. Federal HCPCS descriptors are CMS public data. State manuals and plan contracts change; confirm the current edition before billing.
Frequently asked questions
What is the HK modifier?
HK is the HCPCS Level II modifier "Specialized mental health programs for high-risk populations."
What is the HK modifier for behavioral health in Ohio?
Ohio uses HK for licensed practitioners providing therapeutic behavioral services group hourly or per diem, or SUD intensive outpatient, partial hospitalization, or group counseling.
Does Michigan use HK?
Michigan moved H2014 out-of-home non-vocational habilitation from HK to its state modifier WZ. Check its current code set for other uses.
Program modifiers, applied by level of care.
See Stable apply HK and other program modifiers to group, IOP, and PHP claims by state.
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