Index: firmware/App/Modes/ModeTreatment.c
===================================================================
diff -u -r5046a41e436df0e43e5c9c83eac1bc3a3db20b3c -rf3ecaf3a7bc6d07225791f43196c468ff05ad016
--- firmware/App/Modes/ModeTreatment.c	(.../ModeTreatment.c)	(revision 5046a41e436df0e43e5c9c83eac1bc3a3db20b3c)
+++ firmware/App/Modes/ModeTreatment.c	(.../ModeTreatment.c)	(revision f3ecaf3a7bc6d07225791f43196c468ff05ad016)
@@ -1058,22 +1058,24 @@
     {
         // Always keep the UF volume the same and change the UF rate upon changing the treatment time
         presMaxUFVolumeML = getTreatmentParameterF32( TREATMENT_PARAM_UF_VOLUME ) * (F32)ML_PER_LITER;
-        presUFRate        = presMaxUFVolumeML / (F32)treatmentTime;
 
+        // New UF rate is how much UF is left to be done / remaining treatment time
+        F32 newUFRateMLPM     = ( presMaxUFVolumeML - getTotalMeasuredUFVolumeInMl() ) / (F32)( treatmentTime - CALC_ELAPSED_TREAT_TIME_IN_MIN() );
         U32 dialVolume        = getTreatmentParameterU32( TREATMENT_PARAM_DIALYSATE_FLOW ) * treatmentTime;   // In mL
 
         // The minimum treatment time is either in the range of the institutional record or the 1-minute treatment config has been requested which is an exception
         BOOL isMinTxTimeValid = ( ( treatmentTime >= getU32TreatmentParamLowerRangeLimit( TREATMENT_PARAM_TREATMENT_DURATION ) ) ||
                                   ( TRUE == getTestConfigStatus( TEST_CONFIG_ENABLE_ONE_MINUTE_TREATMENT ) ) ? TRUE : FALSE );
         BOOL isTxTimeValid    = ( ( TRUE == isMinTxTimeValid ) &&
                                   ( treatmentTime <= getU32TreatmentParamUpperRangeLimit( TREATMENT_PARAM_TREATMENT_DURATION ) ) ? TRUE : FALSE );
-        BOOL isUFRateValid    = ( ( presUFRate >= MIN_UF_RATE_ML_MIN ) && ( presUFRate <= MAX_UF_RATE_ML_MIN ) ? TRUE : FALSE );
+        BOOL isUFRateValid    = ( ( newUFRateMLPM >= MIN_UF_RATE_ML_MIN ) && ( newUFRateMLPM <= MAX_UF_RATE_ML_MIN ) ? TRUE : FALSE );
 
         if ( ( TRUE == isTxTimeValid ) && ( dialVolume <= MAX_DIALYSATE_VOLUME_ML ) && ( TRUE == isUFRateValid ) )
         {
             result = TRUE;
             sendTreatmentLogEventData( TREATMENT_DURATION_CHANGE_EVENT, ( presTreatmentTimeSecs / SEC_PER_MIN ), treatmentTime );
             presTreatmentTimeSecs = treatmentTime * SEC_PER_MIN;
+            presUFRate            = newUFRateMLPM;
             setTreatmentParameterF32( TREATMENT_PARAM_UF_VOLUME, ( presMaxUFVolumeML / (F32)ML_PER_LITER ) );
             setTreatmentParameterU32( TREATMENT_PARAM_TREATMENT_DURATION, ( presTreatmentTimeSecs / SEC_PER_MIN ) );
             setDialysisDialInFlowAndUFRate( getTreatmentParameterU32( TREATMENT_PARAM_DIALYSATE_FLOW ), presMaxUFVolumeML, presUFRate );