It depends on what you mean by "protect." The typical trust most people mean when they say Living Trust is a revocable trust, meaning you can revoke it or make changes to it any time. Because of that feature, Living Trusts will not protect your assets from creditors, no matter how long they have been in effect. Usually they will also not be effective by themselves in planning for Medicaid eligibility. (Medicare is not dependent on what your assets are or where they are held-- Medicare is available to almost every U.S. citizen-resident over 65 and some other persons under 65).
An irrevocable trust can be set up for asset protection or Medicaid eligibility. For Medicaid protection the look back period is 5 years. Consult a local elder law attorney because there may be some techniques in addition to or instead of an irrevocable trust that can plan for Medicaid eligibility during the 5 year lookback.
While a Living trust does not protect assets (typically), your home is protected if it is your homestead. As a homestead in a trust, there is no minimum time to offer protection from normal creditors. If you are filing bankruptcy, this is different.
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