It might not even be ALA.
Usually, people eat so many carbs on the carb-up day/s, that when they fast for the 10-12 hrs between let's say Sunday and Monday morning - the blood sugar levels fall so low that Ketones start showing in the urine. Which is a false positive, and, yes, you need to deplete ALL muscle and liver glycogen before you're truly in Ketosis.
Mr.X