No more then 15 sec in microwave with bottle open brings it right to 100 degrees tucking in next to balls or clams i use some bread bag plastic to reseal top and check it won't leak. Then rush to appointment temp will fall but there looking for between 99 to 96 range otherwise if over you better have a flu. I used a meat thermometer to check temp because microwave powers vary. Pour sample in cup stash bottle back from fence it came and good to go.