A system for monitoring ultrafiltration rate during hemodialysis using estimated flow rates, the system comprising: a dialyzer (22, 202) comprising four ports: a first port connected to an arterial blood line, a second port connected to a venous blood line, a third port connected to a dialysate in line, and a fourth port connected to a dialysate out line; four pressure sensors (212-1, 212-2, 212-3, 212-4) coupled to the dialyzer (22, 202), wherein the four pressure sensors (212-1, 212-2, 212-3, 212-4) comprise: a first pressure sensor measuring pressure at the arterial blood line, a second pressure sensor measuring pressure at the venous blood line, a third pressure sensor measuring pressure at the dialysate in line, and a fourth pressure sensor measuring pressure at the dialysate out line; a non-transitory computer readable medium with one or more models stored thereon; and a processor configured to: acquire pressure readings from the four pressure sensors (212-1, 212-2, 212-3, 212-4), apply the pressure readings of the four pressure sensors to the one or more models to determine an estimated flow rate, determine whether the estimated flow rate and the expected flow rate are within a predefined range, and make adjustments and/or generate an alarm in response to determining that the estimated flow rate and the expected flow rate are not within the predefined range. a dialyzer (22, 202) comprising four ports: a first port connected to an arterial blood line, a second port connected to a venous blood line, a third port connected to a dialysate in line, and a fourth port connected to a dialysate out line; four pressure sensors (212-1, 212-2, 212-3, 212-4) coupled to the dialyzer (22, 202), wherein the four pressure sensors (212-1, 212-2, 212-3, 212-4) comprise: a first pressure sensor measuring pressure at the arterial blood line, a second pressure sensor measuring pressure at the venous blood line, a third pressure sensor measuring pressure at the dialysate in line, and a fourth pressure sensor measuring pressure at the dialysate out line; a non-transitory computer readable medium with one or more models stored thereon; and a processor configured to: acquire pressure readings from the four pressure sensors (212-1, 212-2, 212-3, 212-4), apply the pressure readings of the four pressure sensors to the one or more models to determine an estimated flow rate, determine whether the estimated flow rate and the expected flow rate are within a predefined range, and make adjustments and/or generate an alarm in response to determining that the estimated flow rate and the expected flow rate are not within the predefined range. acquire pressure readings from the four pressure sensors (212-1, 212-2, 212-3, 212-4), apply the pressure readings of the four pressure sensors to the one or more models to determine an estimated flow rate, determine whether the estimated flow rate and the expected flow rate are within a predefined range, and or more models to determine an estimated flow rate, determine whether the estimated flow rate and the expected flow rate are within a predefined range, and make adjustments and/or generate an alarm in response to determining that the estimated flow rate and the expected flow rate are not within the predefined range.