My daughter is a 30 yr old adult with special needs. She has Medicaid but we have always maintained private insurance because of her specialized medical needs. Medicaid has been her secondary and won't adequately cover her as primary. Of her 9 doctors only 2 will accept Medicaid.
Question - If one of her parents start on Medicare will that allow her to also get Medicare as a DAC? What allows her to use Medicare as a Primary insurance?

Hi. Yes, if you or your husband claim Social Security retirement or disability benefits and if your daughter qualifies for disabled adult child (DAC) benefits then she'll be eligible for Medicare coverage effective with the 25th month of her entitlement to DAC benefits.

Medicare is automatically a person's primary coverage unless they are covered by an employer group health plan (EGHP) that's based on their own current work, or in some cases a family member's current work. So, unless your daughter is either a) working and covered by her employer's EGHP, or b) she is covered under your or your husband's EGHP that has at least 100 employees (i.e. a large group health plan), then once she qualifies for Medicare that will become her primary coverage.

Best, Jerry