The “official” info can be found on the government’s HIPAA website: http://www.hhs.gov/ocr/hipaa/
From that page, click on the “Am I a covered entity” link, and it will take you to a set of questionnaires. For a sole practitioner, it’s the “Is a Person, Business, or Agency a Covered Health Care Provider?”. The first question asks if you are doing any kind of health care for money. If yes, the next question is, essentially, do you communicate (electronically) with or make use of any healthcare plan for claims. If the answer is “no”, it then states that you are
not covered by HIPAA.
This issue is complicated and opinions vary. This questionnaire should help you answer whether you are a covered entity.