Medicaid and Medicare for substance use and mental health treatment

Medicaid and Medicare pay for a large share of substance use and mental health treatment in the United States, yet both programs confuse almost everyone who encounters them for the first time. The names are similar; the rules are not. This guide explains what each program covers, how to get enrolled, and how to find facilities that actually accept your coverage — without the jargon.

How Medicaid works — and why it varies by state

Medicaid is a joint federal and state program that covers people with limited income. The federal government sets a floor of rules; each state designs its own program on top of that floor. This is why advice that is accurate in one state can be wrong in the next: eligibility categories, covered services, and which facilities participate all differ by state.

The biggest dividing line is expansion. Under the Affordable Care Act, states can extend Medicaid to adults based on income alone. In expansion states, a low income is generally enough to qualify. In states that have not expanded, adults typically must also fit a category — pregnancy, a qualifying disability, or being a parent or caregiver with a very low income — which leaves some people without an affordable coverage path.

What Medicaid covers for substance use disorder also varies, but most state programs cover a meaningful range: outpatient counseling, medication for opioid use disorder, and in many states residential treatment through special federal arrangements. Mental health parity rules apply to Medicaid managed-care plans, which most states now use to deliver benefits. The authoritative source for your state's rules is medicaid.gov and your state Medicaid agency.

How to apply for Medicaid

Unlike marketplace insurance, Medicaid has no annual enrollment window — you can apply any day of the year, and coverage can sometimes apply retroactively to recent medical bills, depending on your state. There are three common ways in:

• Your state Medicaid agency, online, by phone, or in person. This is the most direct route.
• healthcare.gov, which screens your household for Medicaid eligibility automatically and forwards your application to the state if you appear to qualify.
• Through a facility or hospital. Many treatment programs and community health centers have staff who help patients apply as part of intake — it is worth asking whether yours does.

Have documents ready: proof of identity, income, and residence. If you are helping a family member apply, they will generally need to sign or authorize the application themselves.

Finding facilities that accept Medicaid

Enrollment is only half the job; the other half is finding a program that takes your coverage. Publicly funded programs, community health centers, and opioid treatment programs commonly accept Medicaid. Some private facilities — particularly higher-end residential programs — do not, and others accept it only for certain levels of care.

Community health centers deserve special mention here. They are required to serve people regardless of ability to pay, they routinely accept Medicaid, and many now provide behavioral health and substance use services alongside primary care. For someone whose Medicaid application is still pending, a health center's sliding-scale fees can bridge the gap until coverage begins.

Two tools shorten the search. In our directory search, you can filter facilities by accepted payment types, including Medicaid, and every listing shows sourced pricing where we have it. The federal locator at findtreatment.gov also lets you filter by payment accepted. Whichever tool you use, confirm directly with the facility before admission — and if your state delivers Medicaid through managed-care plans, confirm the facility is in your specific plan's network, not just "accepts Medicaid" in general. Our guide on verifying benefits applies to public coverage too.

What Medicare Parts A, B, and D cover

Medicare is the federal program for older adults and some people with disabilities. For substance use and mental health care, its parts divide the work:

Part A: hospital and inpatient care

Part A covers inpatient stays, including inpatient psychiatric care and medically managed withdrawal (detox) when it happens in a hospital setting. If a treatment episode begins with hospitalization, Part A is usually the part paying for the bed. Coverage of freestanding residential programs — treatment centers that are not hospitals — is more limited, which surprises many families; ask the facility to verify benefits for the exact setting before admission.

Part B: outpatient and office-based care

Part B covers the outpatient side: therapy and counseling, psychiatric evaluation, partial hospitalization and intensive outpatient programs, office-based treatment with medications for opioid use disorder, and many telehealth services. For most people, the bulk of a recovery journey — the months of counseling and medication management after any inpatient stay — runs through Part B.

Part D: prescription drugs

Part D plans cover outpatient prescription medications, including medications commonly used in treating substance use disorders and mental health conditions when filled at a pharmacy. Formularies vary by plan, so check that a specific medication is covered before assuming. The official plan-comparison tools live at medicare.gov.

Opioid treatment programs under Medicare

Opioid treatment programs (OTPs) — the licensed programs that can dispense methadone for opioid use disorder — are covered by Medicare under Part B. That coverage bundles the medication itself with the counseling, toxicology testing, and care coordination the program provides. This matters because methadone for opioid use disorder is available only through OTPs, not retail pharmacies, so Part D cannot fill that gap. If you or a family member relies on methadone treatment, look for an OTP enrolled with Medicare and confirm enrollment when you call. Our guide to medication-assisted treatment costs explains what drives pricing for this kind of care, and free and state-funded options exist where coverage falls short.

When you qualify for both

Some people qualify for Medicare and Medicaid at the same time — usually older adults or people with disabilities who also have limited income. For this group, the programs work together: Medicare pays first, and Medicaid can pick up premiums, cost-sharing, and services Medicare does not cover. Dual eligibility often makes treatment substantially more affordable than either program alone, and it can open access to Medicaid-covered services, such as certain residential care, that Medicare would not reach.

If you think you might be dual-eligible, apply for Medicaid through your state agency even if you already have Medicare — the programs enroll separately. Special plans exist for dual-eligible individuals that coordinate both benefits under one card; your state agency or a State Health Insurance Assistance Program counselor can explain the options in your area at no cost. And before choosing a facility, confirm it accepts both coverages — our search lets you filter by payment accepted, and our overview of how insurance covers rehab covers the private-coverage side of the picture.