an implantable blood monitoring and medication administering system includes an infusion device which is implantable beneath the skin of a human or animal and which contains medication . a catheter which is implantable in a vessel v is connected to the infusion device . an information transmitting sensor is located in the catheter and is connected to a microprocessor within the system which controls a pump for first withdrawing blood from the vessel v and submitting it to the sensor and then returning the withdrawn blood to the vessel v along with a predetermined amount of medication , the pump may act to pump medication as well as blood or to pump blood alone . in the latter instance , a second pump acts to pump the medication .