diff --git a/peerprep/backend/question-service/src/middleware/normalizationMiddleware.ts b/peerprep/backend/question-service/src/middleware/normalizationMiddleware.ts
new file mode 100644
index 0000000000..1c98ece1d1
--- /dev/null
+++ b/peerprep/backend/question-service/src/middleware/normalizationMiddleware.ts
@@ -0,0 +1,13 @@
+import { Request, Response, NextFunction } from 'express';
+
+export const normalizeQuestionData = (req: Request, res: Response, next: NextFunction): void => {
+  if (req.body) {
+    if (Array.isArray(req.body.categories)) {
+      req.body.categories = req.body.categories.map((cat: string) => cat.toLowerCase());
+    }
+    if (typeof req.body.difficulty === 'string') {
+      req.body.difficulty = req.body.difficulty.toLowerCase();
+    }
+  }
+  next();
+};
diff --git a/peerprep/backend/question-service/src/server.ts b/peerprep/backend/question-service/src/server.ts
index 3ed070789b..3262ca7ebc 100644
--- a/peerprep/backend/question-service/src/server.ts
+++ b/peerprep/backend/question-service/src/server.ts
@@ -8,6 +8,7 @@ import questionRoutes from './routes/questionRoutes';
 import databaseRoutes from './routes/databaseRoutes';
 import gptRoutes from './routes/gptRoutes';
 import loadSampleData from './sampleData';
+import { normalizeQuestionData } from './middleware/normalizationMiddleware';
 
 connectDB() // Initialize MongoDB connection
   .then(() => {
@@ -43,6 +44,11 @@ app.use(cors({
 } as CorsOptions));
 app.use(express.json());
 
+// Apply normalization middleware to specific routes
+// This middleware will normalize `categories` and `difficulty` fields to lowercase
+app.use('/api/questions', normalizeQuestionData);
+
+
 // API routes
 app.use('/api', questionRoutes);