If your Alfredo sauce leftovers are in the fridge and it's been a few days, you maybe be wondering if it's still good to use. There are a few ways to tell. Because Alfredo sauce is a milk and cheese based sauce, you should be able to tell by the smell. Or if there is mold or water has begun to appear on the top and it just doesn't look the same as when you put in in the refrigerator. I always live by the rule 'when in doubt, throw it out' and that rule definitely applies here!