You may file as head of household only if you meet the following requirements:

  1. You are unmarried or "considered unmarried" on the last day of the year.
  2. You may claim a dependency exemption for your parent.
  3. You paid more than half the cost of keeping up a home for your parent for the tax year. Your dependent parent does not have to live with you.  See "Special rule for parent" in Chapter 2 of Publication 17, Your Federal Income Tax for Individuals under "Qualifying Person." 

See Table 3-1 in Chapter 3 of Publication 17, "Overview of the Rules for Claiming an Exemption for a Dependent," for additional requirements.  See Table 2-1 in Chapter 2 of Publication 17, "Who Is a Qualifying Person Qualifying You to File as Head of Household?."  See also Publication 501, Exemptions, Standard Deduction, and Filing Information