If you become disabled and enroll in Medicare, you must stop making HSA contributions starting the first day of the month in which your Medicare coverage begins. Your HSA will remain active, and you can continue to use the funds to pay for qualified medical expenses, including Medicare Part A and Part B premiums.
Since you are disabled, distributions made for non-qualified medical expenses may not be subject to the 20% penalty and will continue to be tax-free.
Source: IRC Sec. 223(f)(4)(B)
Updated: