Hi.
I hope I did understand your worries right...
It's like a bird sitting on a 100,000 Volts wire. It's not the 100,000V with respect to earth that counts,
There's just a tiny volts between it's feet...nothing harmful.
The same is with the IC. Not high voltage "between" he pins....only the current source transistor.
Every current measurement IC manufacturer gives information about how they work. Either in datasheets or additional documents.
I recommend to read through some of them.
Klaus