Most health insurance plans do cover addiction and mental health treatment. Federal parity law requires insurers to treat these conditions the same way they treat any other medical care, so a policy that covers a hospital stay generally has to cover rehab too. The real questions are more specific. Which levels of care does your plan include, and what will you or your loved one pay out of pocket? Coverage can vary between detox, residential care, and outpatient programs, and that detail is worth checking before you commit.