A method and an apparatus for use in estimating blood flow in an intravascular blood pump comprise retrieving reference data from a set of reference data obtained in a test environment. The set of reference data comprises, for at least one motor speed at different pump loads, including a first pump load, both a reference motor current (I) of a motor driving the blood pump and an amount of fluid flow through the blood pump. After placement of the blood pump in the patient, a patient-specific motor current for said motor speed at said first pump load is measured, and a motor current deviation value (ΔΙ) is calculated from the reference motor current (I) at said first pump load and patient-specific motor current. Finally, the motor current deviation value ΔΙ is used for estimating a patient-specific blood flow amount through the blood pump.
