What is the right temperature to warm up breast milk for baby? If baby finishes the milk only halfway, what do I do with the remainder?

If you are using a bottle warmer, there is an indicator that shows where you should turn to for warming milk which is about 40 degrees celcius and warm it for 4-6 minutes. Any temperature higher than this will break down the nutrients in the milk. Do not warm up the milk in a microwave because uneven pockets of scalding milk can form. The milk will also continue to heat up for some time after you've taken it out of the microwave. Some babies have had burns to the mouth and throat after drinking microwaved milk. If baby finishes the milk halfway, you can keep it at room temperature for 1 hour maximum. Do not put it back into the fridge or refreeze. Or you can organise them in smaller amount so that it will minimise the wastage.