If I have already warmed up the breastmilk, and baby does not complete drinking it, how long can i keep it in the open for? Can I refrigerate after?

Breastmilk that are warmed up and baby's saliva had touched the milk, you can only keep it for 1 hour and cannot refrigerate it again. It will be better if you can warm in smaller amounts i.e. baby drinking amount. Also note that thawed frozen milk must be consume in 24 hours.