Do I have to use the HSA in conjunction with the HDHP?

Yes. In order to qualify for an HSA, the IRS dictates that the employee must be enrolled in a qualified HDHP. IRS regulations for 2019 require the HDHP to have a minimum  deductible of $1,350 for individuals and $2,700 for families. The premium for an HDHP generally costs less than a traditional health care plan, so the money that you save can be put in your HSA. You own and control the money in your HSA and decisions on how to spend the money are made by you.