Can Medicare or Medicaid take my 401k?

The age limit for exclusion of assets is 55. Much depends on your state rules, but at 59 you cannot withdraw from the retirement plan until you are 62 1/2. Your withdrawal rate depends on your life expectancy. That money must be used for your care, then Medicaid pays the rest. Of course they won't take it away from you, but you can't hide it either. Once you pass away, your state may take what is left to recover the payments they have made.