What is the best method for preparing and heating a bottle?

By (embryologist), (embryologist) and (embryologist).
Last Update: 06/25/2024

Baby food is one of the issues that can worry moms and dads, especially if they are first-timers. Bottle feeding, preparation, sterilization and heating are some of the basic aspects to be taken into account, especially in the first months of a baby's life.

It is essential that the milk in the bottle is not too hot to avoid burning the baby's mouth. There are different ways of heating the bottle, being the use of the microwave the least indicated.

Recommendations prior to bottle preparation

First of all, there are a series of fundamental aspects to take into account from the moment you start preparing the bottle for the baby, such as hygiene, for example.

It is important to wash your hands thoroughly with soap and water before handling your child's food.

Make sure that the bottle is correctly sterilized, that the milk is well prepared, that the teat is suitable and that the feeding schedule is taken into account. It is best to prepare each bottle when it is time to feed. If this is not possible, it is best to store the prepared bottle in the refrigerator.

Regarding the nipple, there are different models, although silicone nipples are recommended due to their durability and resistance.

Bottle preparation

Once all the elements are ready, the next step is the preparation of the bottle. At this point it is important to differentiate whether liquid or powdered formula is to be used.

In the case of liquid milk, it will only be necessary to pour the appropriate amount of milk into the bottle and warm it up.

If powdered milk is chosen, then the bottle will take more preparation. For this purpose, it is recommended to use bottled water of weak mineralization. In cases where the drinking water from the tap is soft and of good quality, it could also be used to prepare the bottle. Once the required amount of water has been added, the exact amount of powder is then added according to the label instructions.

It is normal to add one scoop of powdered milk for every 30 mL of water. For example, for a 6-month-old baby, 210-250 mL of bottle per feeding will be needed and the feeding frequency is 4-5 times a day. However, this is totally indicative and will depend on each baby and its weight. Therefore, it is always recommended to follow and respect the amounts recommended by specialists.

Warming the bottle

If the bottle is too cold, the baby may refuse to drink it, while if the milk is too hot, it may cause some kind of burn.

It is recommended that the temperature of the bottle never exceeds 32-36ºC to avoid any type of damage. Sometimes, it is even recommended that the milk be lukewarm rather than hot.

There are temperature gauges that are placed on the back of the bottle and indicate the exact temperature of the bottle. However, the most common way to check if the bottle is at the correct temperature is to pour a few drops of the liquid into your hand.

Another recommendation to keep in mind when heating the bottle is to have some foresight about when the baby should or will want to eat. This will allow enough time for bottle preparation without the baby becoming desperately hungry and crying.

The following are the different ways to warm the bottle.


A few years ago, the most common method for heating bottles for most moms and dads was the bain-marie. This form of heating consists of placing the bottle in a container with water and putting it on the heat. Before the water starts to boil, remove the bottle and wait until the contents are at the right temperature.

This way of heating does not leave cold zones in the bottle (i.e. it is a fairly uniform heating) and does not alter its material of manufacture.

However, using a water bath to warm the bottle is not a quick method.

Bottle warmer

Today you can find a number of bottle warmers on the market that allow you to achieve the right bottle temperature automatically and without any problems. When using the bottle warmer, it is very important to follow the instructions or rules of use.

Depending on the model, certain steps may be required to operate the bottle warmer. Once it has reached the correct or indicated temperature, the appliance is usually turned off.


There is some controversy regarding the use of microwaves to warm baby's milk. Some specialists advise against the use of such an instrument, as it heats the milk unevenly. When heating the bottle in the microwave, you may find areas where the milk gets too hot and others where it stays cold. This can be a danger to the baby since the mother will feel that the bottle is at the right temperature, when in fact it is not.

In addition, the use of microwaves to heat the bottle is also not indicated because microplastics could be released from the bottle and contaminate the milk. However, if the bottle is made of glass, it could be heated in the microwave, although the temperature of the liquid should be tested beforehand to avoid burns.

FAQs from users

Should bottled water be used to prepare the bottle?

By Silvia Azaña Gutiérrez B.Sc., M.Sc. (embryologist).

It would be advisable, especially when the baby is younger, to use bottled water that is weakly mineralized and suitable for the preparation of baby food.

The reason is that in some places the mineralization of tap water may not be adequate.

How do you prepare a bottle of formula for a 3-month-old baby?

By Marta Barranquero Gómez B.Sc., M.Sc. (embryologist).

The steps to prepare a bottle correctly are as follows:

  1. Wash hands with soap and water.
  2. Add bottled water to the bottle. If you live in a geographic area with water suitable for drinking, you can fill the bottle with tap water.
  3. Incorporate the correct amount of milk powder according to the pediatrician's instructions.
  4. Insert the nipple and shake the bottle.
  5. Heat the bottle, mainly in a bain-marie or using a bottle warmer. If possible, it is not advisable to heat the bottle in the microwave.
  6. Check that the bottle is at the right temperature before feeding the baby. To do this, a few drops of milk can be poured into the mother's hand.

Suggested for you

If you are interested in knowing whether artificial milk or breast milk is better, then we invite you to continue reading here: Baby feeding: breast milk or bottle?

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FAQs from users: 'Should bottled water be used to prepare the bottle?' and 'How do you prepare a bottle of formula for a 3-month-old baby?'.

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Authors and contributors

 Marta Barranquero Gómez
Marta Barranquero Gómez
B.Sc., M.Sc.
Graduated in Biochemistry and Biomedical Sciences by the University of Valencia (UV) and specialized in Assisted Reproduction by the University of Alcalá de Henares (UAH) in collaboration with Ginefiv and in Clinical Genetics by the University of Alcalá de Henares (UAH). More information about Marta Barranquero Gómez
License: 3316-CV
 Neus Ferrando Gilabert
Neus Ferrando Gilabert
B.Sc., M.Sc.
Bachelor's Degree in Biology from the University of Valencia (UV). Postgraduate Course in Biotechnology of Human Assisted Reproduction from the Miguel Hernández University of Elche (UMH). Experience managing Embryology and Andrology Labs at Centro Médico Manzanera (Logroño, Spain). More information about Neus Ferrando Gilabert
 Silvia Azaña Gutiérrez
Silvia Azaña Gutiérrez
B.Sc., M.Sc.
Graduate in Health Biology from the University of Alcalá and specialized in Clinical Genetics from the same university. Master in Assisted Reproduction by the University of Valencia in collaboration with IVI clinics. More information about Silvia Azaña Gutiérrez
License: 3435-CV

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