A proposed blood treatment apparatus includes: a blood treatment unit, a pair of fluid pumps and a pair blood pumps. The blood treatment unit is configured to receive untreated blood and fresh blood treatment fluid, and emit treated blood and used blood treatment fluid. The fluid pumps are configured to pass blood treatment fluid through the blood treatment unit. The blood pumps are configured to extract untreated blood from a blood source, pass extracted blood through the blood treatment unit and deliver treated blood to a target vessel. Additionally, the fluid pumps are configured to control the operation of the blood pumps via the blood treatment fluid. Moreover, a flow control device is configured to control a trans-membrane flow between the blood side and the a fluid side of the blood treatment unit. Hence, for instance ultrafiltration can be adjusted to a desired level in a very straightforward manner.