diff --git a/docker/Transformation-Engine/src/test/resources/careconnect-to-ukcore/medicationstatement/expected/MedicationStatementDosageLastChanged-Extension-3to4_000.json b/docker/Transformation-Engine/src/test/resources/careconnect-to-ukcore/medicationstatement/expected/MedicationStatementDosageLastChanged-Extension-3to4_000.json
new file mode 100644
index 0000000..600b476
--- /dev/null
+++ b/docker/Transformation-Engine/src/test/resources/careconnect-to-ukcore/medicationstatement/expected/MedicationStatementDosageLastChanged-Extension-3to4_000.json
@@ -0,0 +1,14 @@
+{
+  "resourceType": "MedicationStatement",
+  "extension": [
+    {
+      "extension": [
+        {
+          "url": "https://fhir.hl7.org.uk/STU3/StructureDefinition/Extension-CareConnect-MedicationDosageLastChanged-1",
+          "valueDateTime": "2020-01-28"
+        }
+      ],
+      "url": "http://fhir.hl7.org/fhir/3.0/StructureDefinition/extension-Extension-CareConnect-MedicationDosageLastChanged-1"
+    }
+  ]
+}
\ No newline at end of file
diff --git a/docker/Transformation-Engine/src/test/resources/careconnect-to-ukcore/medicationstatement/expected/MedicationStatementDosageLastChanged-Extension-3to4_001.json b/docker/Transformation-Engine/src/test/resources/careconnect-to-ukcore/medicationstatement/expected/MedicationStatementDosageLastChanged-Extension-3to4_001.json
new file mode 100644
index 0000000..b155dde
--- /dev/null
+++ b/docker/Transformation-Engine/src/test/resources/careconnect-to-ukcore/medicationstatement/expected/MedicationStatementDosageLastChanged-Extension-3to4_001.json
@@ -0,0 +1,14 @@
+{
+  "resourceType": "MedicationStatement",
+  "extension": [
+    {
+      "extension": [
+        {
+          "url": "https://fhir.hl7.org.uk/STU3/StructureDefinition/Extension-CareConnect-MedicationDosageLastChanged-1",
+          "valueDateTime": "2020-02-25"
+        }
+      ],
+      "url": "http://fhir.hl7.org/fhir/3.0/StructureDefinition/extension-Extension-CareConnect-MedicationDosageLastChanged-1"
+    }
+  ]
+}
\ No newline at end of file
diff --git a/docker/Transformation-Engine/src/test/resources/careconnect-to-ukcore/medicationstatement/expected/MedicationStatementDosageLastChanged-Extension-3to4_002.json b/docker/Transformation-Engine/src/test/resources/careconnect-to-ukcore/medicationstatement/expected/MedicationStatementDosageLastChanged-Extension-3to4_002.json
new file mode 100644
index 0000000..22f267f
--- /dev/null
+++ b/docker/Transformation-Engine/src/test/resources/careconnect-to-ukcore/medicationstatement/expected/MedicationStatementDosageLastChanged-Extension-3to4_002.json
@@ -0,0 +1,14 @@
+{
+  "resourceType": "MedicationStatement",
+  "extension": [
+    {
+      "extension": [
+        {
+          "url": "https://fhir.hl7.org.uk/STU3/StructureDefinition/Extension-CareConnect-GPC-MedicationDosageLastChanged-1",
+          "valueDateTime": "2020-02-25"
+        }
+      ],
+      "url": "http://fhir.hl7.org/fhir/3.0/StructureDefinition/extension-Extension-CareConnect-GPC-MedicationDosageLastChanged-1"
+    }
+  ]
+}
\ No newline at end of file
diff --git a/docker/Transformation-Engine/src/test/resources/careconnect-to-ukcore/medicationstatement/input/MedicationStatementDosageLastChanged-Extension-3to4_000.json b/docker/Transformation-Engine/src/test/resources/careconnect-to-ukcore/medicationstatement/input/MedicationStatementDosageLastChanged-Extension-3to4_000.json
new file mode 100644
index 0000000..c2f5595
--- /dev/null
+++ b/docker/Transformation-Engine/src/test/resources/careconnect-to-ukcore/medicationstatement/input/MedicationStatementDosageLastChanged-Extension-3to4_000.json
@@ -0,0 +1,9 @@
+{
+  "resourceType": "MedicationStatement",
+  "extension": [
+    {
+      "url": "https://fhir.hl7.org.uk/STU3/StructureDefinition/Extension-CareConnect-MedicationDosageLastChanged-1",
+      "valueDateTime": "2020-01-28"
+    }
+  ]
+}
diff --git a/docker/Transformation-Engine/src/test/resources/careconnect-to-ukcore/medicationstatement/input/MedicationStatementDosageLastChanged-Extension-3to4_001.json b/docker/Transformation-Engine/src/test/resources/careconnect-to-ukcore/medicationstatement/input/MedicationStatementDosageLastChanged-Extension-3to4_001.json
new file mode 100644
index 0000000..7f5970b
--- /dev/null
+++ b/docker/Transformation-Engine/src/test/resources/careconnect-to-ukcore/medicationstatement/input/MedicationStatementDosageLastChanged-Extension-3to4_001.json
@@ -0,0 +1,9 @@
+{
+  "resourceType": "MedicationStatement",
+  "extension": [
+    {
+      "url": "https://fhir.hl7.org.uk/STU3/StructureDefinition/Extension-CareConnect-MedicationDosageLastChanged-1",
+      "valueDateTime": "2020-02-25"
+    }
+  ]
+}
diff --git a/docker/Transformation-Engine/src/test/resources/careconnect-to-ukcore/medicationstatement/input/MedicationStatementDosageLastChanged-Extension-3to4_002.json b/docker/Transformation-Engine/src/test/resources/careconnect-to-ukcore/medicationstatement/input/MedicationStatementDosageLastChanged-Extension-3to4_002.json
new file mode 100644
index 0000000..7cef459
--- /dev/null
+++ b/docker/Transformation-Engine/src/test/resources/careconnect-to-ukcore/medicationstatement/input/MedicationStatementDosageLastChanged-Extension-3to4_002.json
@@ -0,0 +1,9 @@
+{
+  "resourceType": "MedicationStatement",
+  "extension": [
+    {
+      "url": "https://fhir.hl7.org.uk/STU3/StructureDefinition/Extensioncoding-CareConnect-GPC-DosageLastChanged-1",
+      "valueDateTime": "2020-02-25"
+    }
+  ]
+}
diff --git a/docker/Transformation-Engine/src/test/resources/careconnect-to-ukcore/medicationstatement/maps/MedicationStatementDosageLastChanged-Extension-3to4.map b/docker/Transformation-Engine/src/test/resources/careconnect-to-ukcore/medicationstatement/maps/MedicationStatementDosageLastChanged-Extension-3to4.map
new file mode 100644
index 0000000..cbb39b6
--- /dev/null
+++ b/docker/Transformation-Engine/src/test/resources/careconnect-to-ukcore/medicationstatement/maps/MedicationStatementDosageLastChanged-Extension-3to4.map
@@ -0,0 +1,23 @@
+map "http://fhir.nhs.uk/StructureMap/MedicationStatementDosageLastChanged-Extension-3to4" = "R3 to R4 conversion for CareConnect MedicationStatement DosageLastChanged extension"
+uses "http://hl7.org/fhir/StructureDefinition/MedicationStatement" alias MedicationStatement as source
+uses "http://hl7.org/fhir/StructureDefinition/MedicationStatement" alias MedicationStatement as target
+
+group MedicationStatement(source src : MedicationStatement, target tgt : MedicationStatement)  {
+    src.extension as ext where $this.url='https://fhir.hl7.org.uk/STU3/StructureDefinition/Extension-CareConnect-MedicationDosageLastChanged-1'
+       -> tgt.extension = create('Extension') as tgtext, 
+       tgtext.url='http://fhir.hl7.org/fhir/3.0/StructureDefinition/extension-Extension-CareConnect-MedicationDosageLastChanged-1' then {
+          ext.value : dateTime as vs -> tgtext.extension = create('Extension') as vt, 
+          vt.url = 'https://fhir.hl7.org.uk/STU3/StructureDefinition/Extension-CareConnect-MedicationDosageLastChanged-1' then {
+             ext.value : dateTime as vs1 -> vt.value = create('dateTime') as vt1, vt1.value = vs1;
+          };
+       };
+
+    src.extension as ext where $this.url='https://fhir.hl7.org.uk/STU3/StructureDefinition/Extensioncoding-CareConnect-GPC-DosageLastChanged-1'
+       -> tgt.extension = create('Extension') as tgtext, 
+       tgtext.url='http://fhir.hl7.org/fhir/3.0/StructureDefinition/extension-Extension-CareConnect-GPC-MedicationDosageLastChanged-1' then {
+          ext.value : dateTime as vs -> tgtext.extension = create('Extension') as vt, 
+          vt.url = 'https://fhir.hl7.org.uk/STU3/StructureDefinition/Extension-CareConnect-GPC-MedicationDosageLastChanged-1' then {
+             ext.value : dateTime as vs1 -> vt.value = create('dateTime') as vt1, vt1.value = vs1;
+          };
+       };
+}