diff --git a/packages/better-auth/src/api/routes/sign-up.ts b/packages/better-auth/src/api/routes/sign-up.ts
index 633273e632..3be303986d 100644
--- a/packages/better-auth/src/api/routes/sign-up.ts
+++ b/packages/better-auth/src/api/routes/sign-up.ts
@@ -11,6 +11,7 @@ import type {
 import type { toZod } from "../../types/to-zod";
 import { parseUserInput } from "../../db/schema";
 import { BASE_ERROR_CODES } from "../../error/codes";
+import { isDevelopment } from "../../utils/env";
 
 export const signUpEmail = <O extends BetterAuthOptions>() =>
 	createAuthEndpoint(
@@ -161,7 +162,9 @@ export const signUpEmail = <O extends BetterAuthOptions>() =>
 					});
 				}
 			} catch (e) {
-				ctx.context.logger.error("Failed to create user", e);
+				if (isDevelopment) {
+					ctx.context.logger.error("Failed to create user", e);
+				}
 				throw new APIError("UNPROCESSABLE_ENTITY", {
 					message: BASE_ERROR_CODES.FAILED_TO_CREATE_USER,
 					details: e,
diff --git a/packages/better-auth/src/db/schema.ts b/packages/better-auth/src/db/schema.ts
index 9463738aa8..046fe4f481 100644
--- a/packages/better-auth/src/db/schema.ts
+++ b/packages/better-auth/src/db/schema.ts
@@ -148,6 +148,10 @@ export function parseInputData<T extends Record<string, any>>(
 				parsedData[key] = fields[key].validator.input.parse(data[key]);
 				continue;
 			}
+			if (fields[key].transform?.input && data[key] !== undefined) {
+				parsedData[key] = fields[key].transform?.input(data[key]);
+				continue;
+			}
 			parsedData[key] = data[key];
 			continue;
 		}
diff --git a/packages/better-auth/src/plugins/username/index.ts b/packages/better-auth/src/plugins/username/index.ts
index d18ff54b67..6239179510 100644
--- a/packages/better-auth/src/plugins/username/index.ts
+++ b/packages/better-auth/src/plugins/username/index.ts
@@ -13,6 +13,7 @@ export const username = () => {
 		INVALID_USERNAME_OR_PASSWORD: "invalid username or password",
 		EMAIL_NOT_VERIFIED: "email not verified",
 		UNEXPECTED_ERROR: "unexpected error",
+		USERNAME_IS_ALREADY_TAKEN: "username is already taken. please try another.",
 	};
 	return {
 		id: "username",
@@ -163,10 +164,43 @@ export const username = () => {
 						required: false,
 						unique: true,
 						returned: true,
+						transform: {
+							input(value) {
+								return value?.toString().toLowerCase();
+							},
+						},
 					},
 				},
 			},
 		},
+		hooks: {
+			before: [
+				{
+					matcher(context) {
+						return context.path === "/sign-up/email";
+					},
+					async handler(ctx) {
+						const username = ctx.body.username;
+						if (username) {
+							const user = await ctx.context.adapter.findOne<User>({
+								model: "user",
+								where: [
+									{
+										field: "username",
+										value: username.toLowerCase(),
+									},
+								],
+							});
+							if (user) {
+								throw new APIError("UNPROCESSABLE_ENTITY", {
+									message: ERROR_CODES.USERNAME_IS_ALREADY_TAKEN,
+								});
+							}
+						}
+					},
+				},
+			],
+		},
 		$ERROR_CODES: TWO_FACTOR_ERROR_CODES,
 	} satisfies BetterAuthPlugin;
 };
diff --git a/packages/better-auth/src/plugins/username/username.test.ts b/packages/better-auth/src/plugins/username/username.test.ts
index 390de9b1d0..63dfeb7a39 100644
--- a/packages/better-auth/src/plugins/username/username.test.ts
+++ b/packages/better-auth/src/plugins/username/username.test.ts
@@ -65,4 +65,14 @@ describe("username", async (it) => {
 		});
 		expect(session?.user.username).toBe("new-username-2");
 	});
+
+	it("should fail on duplicate username", async () => {
+		const res = await client.signUp.email({
+			email: "new-email-2@gamil.com",
+			username: "New-username-2",
+			password: "new-password",
+			name: "new-name",
+		});
+		expect(res.error?.status).toBe(422);
+	});
 });