Index: firmware/App/Modes/StateTxDialysis.c
===================================================================
diff -u -r6c933adfd50a0bc041dc29f4bfa15de5e9f4843a -r75f1ba7637288d1c437cad90cb59c961b4e62151
--- firmware/App/Modes/StateTxDialysis.c	(.../StateTxDialysis.c)	(revision 6c933adfd50a0bc041dc29f4bfa15de5e9f4843a)
+++ firmware/App/Modes/StateTxDialysis.c	(.../StateTxDialysis.c)	(revision 75f1ba7637288d1c437cad90cb59c961b4e62151)
@@ -48,6 +48,7 @@
 static F32 setUFVolumeL;                                        ///< Currently set total ultrafiltration volume (in L) for treatment (from prescription).
 static F32 setUFRateMlMin;                                      ///< Currently set ultrafiltration rate (in mL/min from prescription).
 static OVERRIDE_F32_T measUFVolumeL;                            ///< Current total measured volume (in L) for ultrafiltration .
+static U32 lastUFVolumeUpdateTimestamp;
 
 static BOOL ufPauseRequested;                                   ///< Flag indicates UF pause has been requested by user.
 static BOOL ufResumeRequested;                                  ///< Flag indicates UF resume has been requested by user.
@@ -82,6 +83,7 @@
     measUFVolumeL.ovData     = 0.0F;
     measUFVolumeL.ovInitData = 0.0F;
     measUFVolumeL.override   = OVERRIDE_RESET;
+    lastUFVolumeUpdateTimestamp = 0;
 
     setBloodFlowRate         = 0;
     setDialysateFlowRate     = 0;
@@ -121,6 +123,8 @@
     setAlarmUserActionEnabled( ALARM_USER_ACTION_RINSEBACK, TRUE );
     setAlarmUserActionEnabled( ALARM_USER_ACTION_END_TREATMENT, TRUE );
 
+    lastUFVolumeUpdateTimestamp = getMSTimerCount();
+
     // Set actuators as appropriate for state
     cmdStartGenerateDialysate( setDialysateFlowRate, setUFRateMlMin, 0, //dialTemp,               //TODO: Update temperature with dialTemp when we are ready
                                FALSE, acidConvFactor, bicarbConvFactor, sodium, bicarbonate  );
@@ -505,8 +509,19 @@
  *************************************************************************/
 static void updateUFVolume( void )
 {
-    // Update total UF volume drawn
-    measUFVolumeL.data = 0.0F;  // TODO
+    U32 currentTime = getMSTimerCount();
+    U32 elapsedTimeMs = calcTimeBetween( lastUFVolumeUpdateTimestamp, currentTime );
+
+    lastUFVolumeUpdateTimestamp = currentTime;
+
+    if ( DIALYSIS_UF_STATE == currentDialysisState )
+    {
+        F32 elapsedTimeMin = (F32)elapsedTimeMs / ( (F32)MS_PER_SECOND * (F32)SEC_PER_MIN );
+
+        F32 ufVolumeRemovedMl = setUFRateMlMin * elapsedTimeMin;
+
+        measUFVolumeL.data = measUFVolumeL.data + ( ufVolumeRemovedMl / (F32)ML_PER_LITER );
+    }
 }
 
 /*********************************************************************//**