Error Converting datatype varchar to numeric

Dim queryString As String = "SELECT pointsBalance FROM Accounts WHERE custID = '" & CustId & "'"
       Dim SqlConnectionString As String = My.Settings.LoyaltyConnectionString
       CreateCommand(queryString, SqlConnectionString)

   End Sub

   Public Sub CreateCommand(ByVal queryString As String, ByVal connectionString As String)

       Using connection As New SqlConnection(connectionString)
           connection.Open()
           Dim command As New SqlCommand(queryString, connection)
           Dim reader As SqlDataReader = command.ExecuteReader()
           While reader.Read()
               LabelOutput = reader(0)
           End While
       End Using

   End Sub