A blood fluid removal system comprising: a medium housing defining a major chamber; a blood fluid removal membrane disposed in the medium housing and sealingly dividing the major chamber into first and second minor chambers (133, 137); a first inlet and a first outlet in fluid communication with the first minor chamber, wherein the system is configured such that blood enters the first minor chamber through the first inlet and exits the first minor chamber though the first outlet; a second outlet in fluid communication with the second minor chamber, wherein the system is configured such that fluid removed from the blood exits the second minor chamber through the second outlet; a first sensor configured to detect an indicator of a blood waste product at or downstream of the second outlet, a blood waste product being a compound or component of blood configured to be removed during a blood fluid removal process; and control electronics configured to acquire data from the sensor and configured to determine whether the membrane is functioning within predetermined parameters based on the acquired data; and further comprising a second sensor configured to detect the indicator of a blood waste product at or upstream of the first inlet, wherein the control electronics are configured to acquire data from the second sensor, and wherein the control electronics are configured to compare data acquired from the first sensor to data acquired from the second sensor in determining whether the membrane is functioning within predetermined parameters; and a second inlet in communication with the second minor chamber, wherein dialysate is configured to flow through the second minor chamber from the second inlet to the second outlet; and a dialysate flow controller operably coupled to the control electronics, wherein control electronics are configured to increase dialysate flow rate, via the dialysate flow controller, through the second minor chamber if the membrane is determined not to be functioning within predetermined limits; and further comprising a third sensor configured to detect a blood waste product at or downstream of the first outlet, wherein the control electronics are configured to acquire data from the third sensor, and wherein the control electronics are configured to compare data acquired from the second sensor to data acquired from the third sensor in determining whether the membrane is functioning within predetermined parameters. a medium housing defining a major chamber; a blood fluid removal membrane disposed in the medium housing and sealingly dividing the major chamber into first and second minor chambers (133, 137); a first inlet and a first outlet in fluid communication with the first minor chamber, wherein the system is configured such that blood enters the first minor chamber through the first inlet and exits the first minor chamber though the first outlet; a second outlet in fluid communication with the second minor chamber, wherein the system is configured such that fluid removed from the blood exits the second minor chamber through the second outlet; a first sensor configured to detect an indicator of a blood waste product at or downstream of the second outlet, a blood waste product being a compound or component of blood configured to be removed during a blood fluid removal process; and control electronics configured to acquire data from the sensor and configured to determine whether the membrane is functioning within predetermined parameters based on the acquired data; and further comprising a second sensor configured to detect the indicator of a blood waste product at or upstream of the first inlet, wherein the control electronics are configured to acquire data from the second sensor, and wherein the control electronics are configured to compare data acquired from the first sensor to data acquired from the second sensor in determining whether the membrane is functioning within predetermined parameters; and a second inlet in communication with the second minor chamber, wherein dialysate is configured to flow through the second minor chamber from the second inlet to the second outlet; and a dialysate flow controller operably coupled to the control electronics, wherein control electronics are configured to increase dialysate flow rate, via the dialysate flow controller, through the second minor chamber if the membrane is determined not to be functioning within predetermined limits; and further comprising a third sensor configured to detect a blood waste product at or downstream of the first outlet, wherein the control electronics are configured to acquire data from the third sensor, and wherein the control electronics are configured to compare data acquired from the second sensor to data acquired from the third sensor in determining whether the membrane is functioning within predetermined parameters.