What constitutes a high deductible health plan? What form would I need to look for to find this information?

here's the page I got the info from

https://20somethingfinance.com/what-is-a-high-deductible-health-plan-hdhp/

or

https://www.healthcare.gov/glossary/high-deductible-health-plan/

or 

IRC section 223(c)(2)

The IRS describes an HDHP (High Deductible Health Plan) in Publication 969 on pages 3 and 4. An HDHP is more than just the high deductible; there are some other subtleties that have to be considered, such as plans where the interaction between the individual and family deductibles can cause the plan to fail the IRS' definition of an HDHP.

Such subtleties can be difficult for the non-insurance professional (i.e., most taxpayers) to discern. Fortunately, there is an easy solution - call your insurance carrier. Your insurance carrier certainly knows whether or not the plan you are on is an HDHP. In fact, it is likely that the letters HDHP are printed on the insurance card that they sent you. But even if HDHP isn't on the card, there is certainly a telephone number that you can call and get the answer in a couple of minutes.