I would like to know if I can sue someone for saying I'm HIV positive, if I'm not. This was said to me over the phone. It's my word against hers.
Despite the fact that we live in litigious times, you cannot sue someone for saying something to you that you don't like or that isn't true. You might be thinking about defamation, which is when someone says something that isn't true about you to a third person.
A successful defamation lawsuit generally requires an untrue statement made to a third person which causes reputational or other types of damage. Under the law, some statements are so offensive that you may not even need to prove damages, just that the statement was made.
Rather than trying to seek retribution for this false statement, I encourage you to examine why you are so upset by it. While I understand that you may not appreciate an untrue statement about your health, I hope your reaction is not driven by HIV stigma. As a community that cares about people living with HIV, we all need to do our part to recognize and eliminate HIV stigma, which is fueling the AIDS epidemic.