What is an IFR medical?
This is somewhat of a trick question. There are no additional medical requirements when exercising the privileges of an Instrument Rating; however under Basic Med rules, a pilot may fly IFR, but at or below 18,000 feet MSL. If you want to fly above that altitude (where IFR is required) then you will need to hold at least a third class medical certificate.
Sporty's Instrument Rating Course