diff --git a/helper.go b/helper.go
index 169c53a..70e9952 100644
--- a/helper.go
+++ b/helper.go
@@ -4,7 +4,6 @@ import (
 	"encoding/hex"
 	"errors"
 	"fmt"
-	"strings"
 )
 
 // Helper function to encode timestamp into the UUID byte array.
@@ -29,14 +28,32 @@ func decodeTimestamp(uuidBytes []byte) uint64 {
 		uint64(uuidBytes[3])<<16 | uint64(uuidBytes[4])<<8 | uint64(uuidBytes[5])
 }
 
+// Helper function to parse and sanitize a UUID string.
 // Helper function to parse and sanitize a UUID string.
 func parseUUID(uuid string) ([]byte, error) {
-	uuid = strings.ReplaceAll(uuid, "-", "")
-	if len(uuid) != 32 {
+	switch len(uuid) {
+	case 32:
+		// Fast path for UUIDs without dashes
+		return hex.DecodeString(uuid)
+	case 36:
+		// Validate dash positions
+		if uuid[8] != '-' || uuid[13] != '-' || uuid[18] != '-' || uuid[23] != '-' {
+			return nil, errors.New("invalid UUID format")
+		}
+
+		// Remove dashes while copying characters
+		result := make([]byte, 32)
+		j := 0
+		for i := 0; i < len(uuid); i++ {
+			if uuid[i] != '-' {
+				result[j] = uuid[i]
+				j++
+			}
+		}
+		return hex.DecodeString(string(result))
+	default:
 		return nil, errors.New("invalid UUID length")
 	}
-
-	return hex.DecodeString(uuid)
 }
 
 // Helper function to check if a UUID is all zeros.
diff --git a/uuidv8_test.go b/uuidv8_test.go
index 34c379d..e9ef3e3 100644
--- a/uuidv8_test.go
+++ b/uuidv8_test.go
@@ -720,3 +720,75 @@ func TestUUIDv8_Scan_EdgeCases(t *testing.T) {
 		})
 	}
 }
+
+func TestFromString_InvalidInputs(t *testing.T) {
+	tests := []string{
+		"123",                                    // Too short
+		"123e4567e89b12d3a4564266141740000000",   // Too long
+		"123e4567e89b12d3a45642661417400g",       // Invalid character
+		"123e-4567-e89b-12d3-a456-426614174000",  // Misplaced dashes
+		"123e4567-e89b-12d3-a456-426614174000-",  // Extra dash at the end
+		"--123e4567-e89b-12d3-a456-426614174000", // Extra dash at the start
+		"123e4567-e89b-12d3-a456-42-6614174000",  // Randomly placed dash
+		"------------------------------------",   // 36 dashes
+		"9a3d4049-0e2c-8080-0102-030405060000",   // Valid UUID with dashes
+	}
+
+	for _, input := range tests {
+		t.Run("Testing UUID: "+input, func(t *testing.T) {
+			_, err := uuidv8.FromString(input)
+			// The last case is valid; others should fail
+			if input == "9a3d4049-0e2c-8080-0102-030405060000" {
+				if err != nil {
+					t.Errorf("Expected valid UUID but got error for input: %s", input)
+				}
+			} else {
+				if err == nil {
+					t.Errorf("Expected error, got nil for input: %s", input)
+				}
+			}
+		})
+	}
+}
+
+func TestFromStringOrNil_InvalidInputs(t *testing.T) {
+	tests := []string{
+		"123",                                    // Too short
+		"123e4567e89b12d3a4564266141740000000",   // Too long
+		"123e4567e89b12d3a45642661417400g",       // Invalid character
+		"",                                       // Empty string
+		"123e4567-e89b-12d3-a456-426614174000-",  // Extra dash at the end
+		"--123e4567-e89b-12d3-a456-426614174000", // Extra dash at the start
+		"123e4567-e89b-12d3-a456-42-6614174000",  // Randomly placed dash
+	}
+
+	for _, input := range tests {
+		t.Run("Invalid UUID "+input, func(t *testing.T) {
+			result := uuidv8.FromStringOrNil(input)
+			if result != nil {
+				t.Errorf("Expected nil for input: %s, got %v", input, result)
+			}
+		})
+	}
+}
+
+func TestIsValidUUIDv8_InvalidUUIDs(t *testing.T) {
+	invalidUUIDs := []string{
+		"123",                                    // Too short
+		"123e4567e89b12d3a4564266141740000000",   // Too long
+		"123e4567e89b12d3a45642661417400g",       // Invalid character
+		"",                                       // Empty string
+		"123e4567-e89b-12d3-a456-426614174000-",  // Extra dash at the end
+		"--123e4567-e89b-12d3-a456-426614174000", // Extra dash at the start
+		"123e4567-e89b-12d3-a456-42-6614174000",  // Randomly placed dash
+
+	}
+
+	for _, uuid := range invalidUUIDs {
+		t.Run("Invalid UUID "+uuid, func(t *testing.T) {
+			if uuidv8.IsValidUUIDv8(uuid) {
+				t.Errorf("Expected UUID %s to be invalid", uuid)
+			}
+		})
+	}
+}