For Medicaid purposes, MAGI is adjusted gross income (AGI) plus these, if any:
untaxed foreign income, non-taxable Social Security benefits, and tax-exempt interest.
A contribution to your Traditional IRA (same as Deductible IRA) does reduce your Medicaid MAGI. Contributions to a Traditional 401k also reduce your Medicaid MAGI.
See: https://www.healthcare.gov/income-and-household-information/income/
