Blood Coin

Similar to cryptocurrency, a blood gem is made to store the unique identifier to a person's wallet. If a person knows a summon spell, it's impossible to steal, unless warded. DNA-locked to one individual. For companies, they can pool an amalgam of gems to represent the company heart. Once a gem is shattered, it cannot be accessed anymore.
Size of gem depends of volume of blood. Blood banks can also create gems. A portion of made into a gem, more of it is donated to hospitals.

Each transactions shaves a bit of the gem off.

All currency is held by a public ledger. A physical space where all the info of a transaction is recorded magically and electronically. Each country has their own. And banks can remotely access and contribute to the ledger.
At banks, a certified hemathurge can create new BGC for customers and register to the ledger. The only kind of blood magic allowed.

The currency name: hema? Hemacoin? New meaning to blood sweat and tears.