If I recall correctly an HSA (Health Savings Account) is linked to your insurance, typically Obama care or similar types of healthcare (high deductible style) - while a FSA (Flexible Spending Account) is "used" in a similar manner but not linked to insurance- meaning you can have one and not have health insurance per say. Both are generally used and funded in order to take care of common and predictable medical expenses- such as if I know I have a monthly prescription of whatever that's 10$ a month, I should fund my HSA or FSA with 120$ to cover that and also get a 120$ tax shelter at the same time- this is mostly lined up to cover the high deductible with "most" now "common" healthcare styles- if your deductible is 500 per visit and caps at 5k in the year, they typically "suggest" you fund your HSA with 5000$ in the beginning and then depending on rollover rules keep the balance there or close- again depending on other predictable medical expenses.
When the doc heard HSA - that means the charge usually is going to be associated with a insurance claim, and as we know when a Doc does that- its the insurance agreed price that's going to be used- if its NOT an HSA but a FSA card- it acts more like a "regular" card and you have to (depending on the vendor) provide documentation with the FSA vendor to prove the charge falls within the acceptable charges. And that is why, most likely- the Doc had to charge you "full price" versus a discounted rate when using an HSA.
