I won't microwave a bottle that already has formula in it. I've got no idea if it's going to have an impact on anything, but I just won't.

Sam likes his bottles warm, too. And our formula just doesn't mix in well if the water is cold (nan HA 2 - bit better than 1, but still hard to mix).

What we do is keep cooled, boiled water in the kettle, then flick it on for about 30 seconds to warm it when we are about to make a bottle up. I keep some cooled, boiled water in a container as well so that if it ends up too hot I can mix in some cooler water.

On occasions I do microwave. Generally when I've gone out and had a bottle of water that's gone cold - I'll take the top off and just microwave the water for 30 seconds and then add the formula. The number of parents rooms that only have a microwave is just ridiculous. We started by taking a plastic cup to heat water in the microwave and then heat our bottle in the cup, but as Sam got bigger and so did his bottles, heating things that way got slow and difficult.

BW