Index: firmware/App/Modes/Dialysis.c
===================================================================
diff -u -r054fa08b67ed2a31f7848b179fbcd1b4da501b0f -rd86855d12f5103fc16e2e06e267da237c8d549d7
--- firmware/App/Modes/Dialysis.c	(.../Dialysis.c)	(revision 054fa08b67ed2a31f7848b179fbcd1b4da501b0f)
+++ firmware/App/Modes/Dialysis.c	(.../Dialysis.c)	(revision d86855d12f5103fc16e2e06e267da237c8d549d7)
@@ -209,6 +209,22 @@
 
 /*********************************************************************//**
  * @brief
+ * The getUltrafiltrationVolumeCollected function gets the current ultrafiltration \n
+ * volume collected so far for current treatment.
+ * @details
+ * Inputs : measUFVolume, measUFVolumeFromPriorReservoirs
+ * Outputs : none
+ * @return currentUFState
+ *************************************************************************/
+F32 getUltrafiltrationVolumeCollected( void )
+{
+    F32 result = measUFVolume + measUFVolumeFromPriorReservoirs;
+
+    return result;
+}
+
+/*********************************************************************//**
+ * @brief
  * The pauseUF function pauses ultrafiltration.
  * @details
  * Inputs : currentDialysisState, currentUFState
Index: firmware/App/Modes/Dialysis.h
===================================================================
diff -u -re0e66d4c302c2aa43951ca316689ed4debbff1fb -rd86855d12f5103fc16e2e06e267da237c8d549d7
--- firmware/App/Modes/Dialysis.h	(.../Dialysis.h)	(revision e0e66d4c302c2aa43951ca316689ed4debbff1fb)
+++ firmware/App/Modes/Dialysis.h	(.../Dialysis.h)	(revision d86855d12f5103fc16e2e06e267da237c8d549d7)
@@ -76,6 +76,7 @@
 
 DIALYSIS_STATE_T getDialysisState( void );
 UF_STATE_T getUltrafiltrationState( void );
+F32  getUltrafiltrationVolumeCollected( void );
 
 BOOL pauseUF( void );
 BOOL resumeUF( void );
Index: firmware/App/Modes/ModeTreatment.c
===================================================================
diff -u -r054fa08b67ed2a31f7848b179fbcd1b4da501b0f -rd86855d12f5103fc16e2e06e267da237c8d549d7
--- firmware/App/Modes/ModeTreatment.c	(.../ModeTreatment.c)	(revision 054fa08b67ed2a31f7848b179fbcd1b4da501b0f)
+++ firmware/App/Modes/ModeTreatment.c	(.../ModeTreatment.c)	(revision d86855d12f5103fc16e2e06e267da237c8d549d7)
@@ -47,8 +47,9 @@
 
 #define TREATMENT_TIME_DATA_PUB_INTERVAL        ( MS_PER_SECOND / TASK_GENERAL_INTERVAL )   ///< Interval (ms/task time) at which the treatment time & state data is published on the CAN bus
 
-#define CALC_ELAPSED_TREAT_TIME_IN_SECS()     ( treatmentTimeMS / MS_PER_SECOND )           ///< Macro to calculate the elapsed treatment time in seconds.
-#define CALC_TREAT_TIME_REMAINING_IN_SECS()   ( (S32)presTreatmentTimeSecs - (S32)( treatmentTimeMS / MS_PER_SECOND ) )   ///< Macro to calculate the remaining treatment time in seconds.
+#define CALC_ELAPSED_TREAT_TIME_IN_SECS()       ( treatmentTimeMS / MS_PER_SECOND )           ///< Macro to calculate the elapsed treatment time in seconds.
+#define CALC_ELAPSED_TREAT_TIME_IN_MIN()        ( ( treatmentTimeMS / MS_PER_SECOND ) / SEC_PER_MIN )  ///< Macro to calculate the elapsed treatment time in minutes.
+#define CALC_TREAT_TIME_REMAINING_IN_SECS()     ( (S32)presTreatmentTimeSecs - (S32)( treatmentTimeMS / MS_PER_SECOND ) )   ///< Macro to calculate the remaining treatment time in seconds.
 
 // ********** private data **********
 
@@ -367,13 +368,15 @@
     OP_MODE currMode = getCurrentOperationMode();
 
     // check if we are in an appropriate treatment state for settings adjustment
-    if ( ( MODE_TREA == currMode ) && ( currentTreatmentState > TREATMENT_START_STATE ) && ( currentTreatmentState < TREATMENT_DIALYSIS_END_STATE ) )
-    {
+    if ( ( MODE_TREA == currMode ) &&
+         ( currentTreatmentState > TREATMENT_START_STATE ) && ( currentTreatmentState < TREATMENT_DIALYSIS_END_STATE ) &&
+         ( CALC_ELAPSED_TREAT_TIME_IN_MIN() < treatmentTime ) )
+    { // TODO - reject if proposed time is < current time   REQUEST_REJECT_REASON_TREATMENT_TIME_LESS_THAN_CURRENT
         F32 uFVolume;
         U32 dialVolume = presDialysateFlowRate * treatmentTime;   // in mL
 
         // always adjust UF volume to accommodate treatment time change (not UF rate)
-        uFVolume = (F32)treatmentTime * presUFRate;
+        uFVolume = ( (F32)( treatmentTime - CALC_ELAPSED_TREAT_TIME_IN_MIN() ) * presUFRate ) + getUltrafiltrationVolumeCollected();
         if ( ( treatmentTime <= MAX_TREATMENT_TIME_MINUTES ) && ( dialVolume <= MAX_DIALYSATE_VOLUME_ML ) )
         {
             result = TRUE;
@@ -400,10 +403,14 @@
         {
             rejectReason = REQUEST_REJECT_REASON_TREATMENT_TIME_OUT_OF_RANGE;
         }
-        else
+        else if ( ( currentTreatmentState <= TREATMENT_START_STATE ) || ( currentTreatmentState >= TREATMENT_DIALYSIS_END_STATE ) )
         {
             rejectReason = REQUEST_REJECT_REASON_INVALID_TREATMENT_STATE;
         }
+        else
+        {
+            rejectReason = REQUEST_REJECT_REASON_TREATMENT_TIME_LESS_THAN_CURRENT;
+        }
     }
     sendChangeUFSettingsResponse( result, rejectReason, pendingUFVolumeChange, pendingTreatmentTimeChange, pendingUFRateChange, timeDiff, rateDiff );