The best method of warming up a feed is by standing the bottle in a container of warm water. The time it takes to heat up the formula to the desired temperature will obviously be dependent on the temperature of the water and the volume of feed you’re heating up so this may just be a matter of testing until you get your system set up.
"NEVER use a microwave to heat up your baby’s formula. Microwaves can heat milks unevenly and can create ‘hot spots’ which can easily burn your baby’s mouth."
It is not ideal to make up powdered formula in advance and then heat it up when you’re ready to use it. Preparation instructions on some packs do highlight this and recommend making up baby formula as you’re ready to use it.
There are of course times when you can use ‘Ready to Drink’ formula – which is ready-made formula in tetra packs, and these can be heated if you wish. It is important not to heat the baby formula in the tetra pack – you must pour the formula into a sterilised bottle to warm it up. Always follow the manufacturer’s instructions.
IMPORTANT NOTICE: Breast milk is best for babies and provides ideal nutrition. Good maternal nutrition is important for the preparation and maintenance of breastfeeding. Introducing partial bottle feeding could negatively affect breastfeeding and reversing a decision not to breastfeed is difficult. Professional advice should be followed on infant feeding. Infant formula should be prepared and used exactly as directed or it could pose a health hazard. The preparation requirements and cost of providing infant formula until 12 months of age should be considered before making a decision to formula feed.