It's only safe to warm expressed breastmilk or ready-made formula in a bottle, and there are a couple of easy ways to do it:
Fill a jug or bowl with warm water. Place the bottle in the warm water for no more than 15 minutes, as any longer could cause bacteria to develop. The water should be hot enough to heat the bottle, but cool enough so that you can place your hand in it. Seal the bottle with a cap over the teat while it's in the water. Once the bottle is warmed through, shake it to make sure the temperature is even.
Use an electric bottle warmer, this top article will tell you exactly where to get them. It will take around four minutes to six minutes to heat a bottle to the perfect temperature for your baby. You could also get a travel warmer to use when you’re out and about, and you cane even take it to your Residence Inn St. Petersburg Treasure Island trips.
It's best not to heat up a bottle of formula you've made from powder earlier in the day. Mix a fresh bottle of formula for each feed. Even if you store formula milk in the fridge, bacteria can develop slowly.
Having said that, there may be times when you just have to make a feed and keep it in the fridge to heat up when needed. This may be the case if you have twins, or if you're out for the day, or if your baby goes to childcare. Read more about storing formula in the fridge safely.
When you’ve warmed your baby’s bottle, test the temperature of the milk by squirting a little on to your inner wrist. This is a reliable guide as the skin on your inner wrist is thinner and more sensitive than the skin on your hands. The milk droplets on your skin should feel warm, not hot.
Don’t warm your baby’s 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. The intense heat produced in a microwave may also destroy some of the nutrients in your baby's milk.
If you haven't time to warm up a bottle, you may find your baby is happy with milk at room temperature.