diff --git a/lib/services/medipostXML.service.ts b/lib/services/medipostXML.service.ts
index ad6fb04..3b55506 100644
--- a/lib/services/medipostXML.service.ts
+++ b/lib/services/medipostXML.service.ts
@@ -62,9 +62,19 @@ export async function composeOrderXML({
       'id',
     );
 
-  const specimenSection = [];
-  const analysisSection = [];
-  let order = 1;
+  // First, collect all unique materials across all analysis groups
+  const uniqueMaterials = new Map<string, {
+    MaterjaliTyypOID: string;
+    MaterjaliTyyp: string;
+    MaterjaliNimi: string;
+    ProovinouKoodOID?: string;
+    ProovinouKood?: string;
+    order: number;
+  }>();
+
+  let specimenOrder = 1;
+
+  // Collect all materials from all analysis groups
   for (const currentGroup of analysisGroups) {
     let relatedAnalysisElement = analysisElements?.find(
       (element) => element.analysis_groups.id === currentGroup.id,
@@ -89,31 +99,86 @@ export async function composeOrderXML({
 
     for (const group of relatedAnalysisElement?.material_groups as MaterjalideGrupp[]) {
       const materials = toArray(group.Materjal);
-      const specimenXml = materials.flatMap(
-        ({ MaterjaliNimi, MaterjaliTyyp, MaterjaliTyypOID, Konteiner }) => {
-          return toArray(Konteiner).map((container) =>
-            getSpecimen(
+      for (const material of materials) {
+        const { MaterjaliNimi, MaterjaliTyyp, MaterjaliTyypOID, Konteiner } = material;
+        const containers = toArray(Konteiner);
+        
+        for (const container of containers) {
+          // Use MaterialTyyp as the key for deduplication
+          const materialKey = MaterjaliTyyp;
+          
+          if (!uniqueMaterials.has(materialKey)) {
+            uniqueMaterials.set(materialKey, {
               MaterjaliTyypOID,
               MaterjaliTyyp,
               MaterjaliNimi,
-              order,
-              container.ProovinouKoodOID,
-              container.ProovinouKood,
-            ),
-          );
-        },
-      );
+              ProovinouKoodOID: container.ProovinouKoodOID,
+              ProovinouKood: container.ProovinouKood,
+              order: specimenOrder++,
+            });
+          }
+        }
+      }
+    }
+  }
 
-      specimenSection.push(...specimenXml);
+  // Generate specimen section from unique materials
+  const specimenSection = Array.from(uniqueMaterials.values()).map(material =>
+    getSpecimen(
+      material.MaterjaliTyypOID,
+      material.MaterjaliTyyp,
+      material.MaterjaliNimi,
+      material.order,
+      material.ProovinouKoodOID,
+      material.ProovinouKood,
+    )
+  );
+
+  // Generate analysis section with correct specimen references
+  const analysisSection = [];
+  for (const currentGroup of analysisGroups) {
+    let relatedAnalysisElement = analysisElements?.find(
+      (element) => element.analysis_groups.id === currentGroup.id,
+    );
+    const relatedAnalyses = analyses?.filter((analysis) => {
+      return analysis.analysis_elements.analysis_groups.id === currentGroup.id;
+    });
+
+    if (!relatedAnalysisElement) {
+      relatedAnalysisElement = relatedAnalyses?.find(
+        (relatedAnalysis) =>
+          relatedAnalysis.analysis_elements.analysis_groups.id ===
+          currentGroup.id,
+      )?.analysis_elements;
+    }
+
+    if (!relatedAnalysisElement || !relatedAnalysisElement.material_groups) {
+      throw new Error(
+        `Failed to find related analysis element for group ${currentGroup.name} (id: ${currentGroup.id})`,
+      );
+    }
+
+    // Find the specimen order number for this analysis group
+    let specimenOrderNumber = 1;
+    for (const group of relatedAnalysisElement?.material_groups as MaterjalideGrupp[]) {
+      const materials = toArray(group.Materjal);
+      for (const material of materials) {
+        const materialKey = material.MaterjaliTyyp;
+        const uniqueMaterial = uniqueMaterials.get(materialKey);
+        if (uniqueMaterial) {
+          specimenOrderNumber = uniqueMaterial.order;
+          break; // Use the first material's order number
+        }
+      }
+      if (specimenOrderNumber > 1) break; // Found a specimen, use it
     }
 
     const groupXml = getAnalysisGroup(
       currentGroup.original_id,
       currentGroup.name,
-      order,
+      specimenOrderNumber,
       relatedAnalysisElement,
     );
-    order++;
     analysisSection.push(groupXml);
   }