Infant formula preparation, storage, and use

How do I prepare, store, and give infant formula?

It is very important to prepare and store infant formula safely. If you don’t, it may become contaminated with bacteria and other microbes or may be too rich or too weak and the baby’s health may suffer. Taking extra care to ensure that infant formula is not contaminated with bacteria and other microbes is especially important if the baby was born small or premature or has a weakened immune system. Babies under the age of four months are also at increased risk of infection. Infant formula should always be prepared with safe water that has been boiled. If used for babies under four months of age and possibly older ones, powdered infant formula should be prepared using water that has been boiled for two minutes and then cooled to no less than 70 degrees Celsius (160 degrees Fahrenheit). Infant formula preparation tools should be disinfected before use.

A) Why proper infant formula preparation is important

It is extremely important that infant formula (formula) is safely prepared and stored. Errors are a common cause of infant illness and may be due to (Ellison 2017; Herbold 2008; Labiner-Wolfe 2008; Malek 2018):

  • Difficulty reading directions (Hormann 2010).
  • Not following recommendations on sterile preparation.
  • Adding too much or too little water.
  • Not using water that has been boiled for two minutes and then cooled to no less than 70 degrees Celsius (160 degrees Fahrenheit) to prepare powdered formula.
  • Not following recommendations on storage of prepared formula.
  • Using inappropriate or contaminated water.

These can result in a baby receiving formula that is:

  • Too rich and concentrated.
  • Too watery and low in calories.
  • Contaminated with:
    • Bacteria and other microbes.
    • Other items that can potentially harm the baby.

One American study (Altazan 2019) of prepared powdered formula showed that roughly only one in five bottles were prepared with the correct amount of added water. About 80% of the formula was too rich and a further 3% was too weak.

Some caregivers receive limited information (Appleton 2020; Ellison 2017; Labiner-Wolfe 2008). Make sure you have all the necessary information you need. Not having a clear understanding of the process can be stressful for you and dangerous for your baby (Lakshman 2009).

There are many online resources describing safe formula use (WHO/UNICEF 2007). Your local health authority and health-care providers should have information relevant to your area and your situation.

B) Babies who are at risk of infection

Bacteria and other microbes can contaminate formula. These can originate in powdered formula, water, or in bottle-feeding supplies and other equipment used to prepare formula. Some babies are more at risk of infection from contaminated formula.

Babies at the highest risk of infection are those who:

  • Are premature.
  • Were born small and are under two months of age.
  • Have a weakened immune system and more likely to get sick if exposed to bacteria and other microbes.

Healthy babies under four months of age are at higher risk of infection than older ones.

C) Disinfecting bottle-feeding supplies

It is safest to disinfect bottle-feeding supplies for as long as your baby is using formula. Bottle-feeding supplies are always disinfected for babies at increased risk of infection and for those younger than four months and possibly for older ones. Improperly cleaned bottles can be a source of dangerous microbes (Redmond 2009).

To disinfect bottle-feeding supplies, caregivers need to:

  1. Wash their hands using soap and hot water (Cho 2019).
  2. Clean the preparation area by wiping it with a clean dish cloth, soap, and warm water. It can be sanitized by spraying it with a bleach mixture (5 millilitres [1 teaspoon] of bleach to 750 ml [3 cups] of water). This can be kept in a spray bottle. Wipe the area dry with a clean towel.
  3. Wash all bottles, nipples, rings, caps, discs, measuring cups, can opener if needed, mixing utensils, and tongs in hot soapy water. If needed, containers for storing boiled water should also be washed. Bottles and nipples should be washed with a dedicated brush to remove any traces of formula.
  4. Rinse the items well with hot water and let them dry on a clean towel.
  5. To disinfect bottles and equipment, fill a large pot with clean water and let the pot boil for five minutes without a lid. Use the disinfected tongs to remove the equipment and shake off the excess water. Allow these to dry on a clean towel. Assemble the bottles without touching the parts that will be in contact with formula.
  6. Store in a clean dry place between two clean towels, in a clean container, or in a plastic bag.

Bottle liners should not be cleaned or reused.

Bleach should be properly stored and kept away from children.

D) Water used to prepare infant formula

1) Choosing a water source

The following types of water can be used to prepare powdered or liquid concentrate formula.

  • Tap water that has been tested for total coliform bacteria, E. coli, and nitrate and other chemicals that may be present in your area.
  • Private or well water that is regularly tested for bacteria and chemicals to ensure it is safe.
  • Sealed plain bottled water.

If tap or well water in your area is safe, cold water should be used instead of hot, as it is less likely to contain toxins.

2) Unsafe or risky water sources

The following types of water should not be used for formula preparation because they contain ingredients that can pose a risk to the baby:

  • Softened water (contains sodium)
  • Water known to contain high levels of nitrate, fluoride, sodium, lead, blue-green algae, or other contaminants (Fossen Johnson 2020)
  • Tap water from an older home that has not been tested for lead
  • Mineral water (various minerals)
  • Carbonated (fizzy) water (salt, sugar)

Lead levels in water should be below 0.10 milligram/litre. It can be leached out of lead pipes present in older houses and municipal water systems (Levallois 2018).

The safety of other types of water may be uncertain.

 

E) Preparing powdered infant formula

1) Getting ready

Before preparing powdered formula:

  • Wash hands with soap and warm water.
  • Disinfect the counter areas.
  • Assemble:
    • The necessary disinfected tools and bottles.
    • Appropriate safe water.

2) Preparing water

Powdered formula is not sterile. It is safest to (WHO 2007) boil water for two minutes and cool to no less than 70°Celcius (C) (160°Fahrenheit [F]) (Silano 2016).

For a rough guide, one litre of water cools to about 70°C (160°F) after about 30 minutes but this varies with room temperature, pot size, and amounts of water. A thermometer should be used for accuracy.

3) Mixing powdered infant formula

To mix powdered formula: 

  • Read the label to see how much formula and boiled water to use.
  • Pour the right amount of water into a disinfected measuring cup.
  • Measure the amount of formula powder using the scoop provided. 
  • Stir using a disinfected spoon until there are no more lumps.
  • Pour the formula into a disinfected bottle.
  • Use disinfected tongs to assemble the nipple parts on the bottle.
  • Tighten the ring without touching the nipple.

4) Risks of using water cooler than 70°C (160°F)

Instead of using water that is hotter than 70°C (160°F), some caregivers choose to use previously boiled water that is cooled and stored in disinfected, closed containers (Carletti 2008).

This increases the risk of infection of the baby as powdered formula may contain bacteria and other microbes which would otherwise be killed by hot water. This practice should be avoided until the baby is at least four months of age and not at increased risk of infection. Formula prepared in this manner should be used immediately and not stored.

F) Preparing liquid concentrate infant formula

1) Getting ready

Before preparing formula from liquid concentrate:

  • Wash your hands with soap and warm water.
  • Disinfect the counter areas.
  • Assemble:
    • The necessary disinfected tools and bottles.
    • Appropriate safe water.

2) Preparing water

Liquid concentrate is sterile until opened. It needs to be combined with safe water before use. Use water that is boiled for two minutes and cooled.

If travelling, boiled water from home can be stored in a tightly closed sterilized container for 2 days in the refrigerator or 24 hours at room temperature.

3) Mixing liquid concentrate formula

To mix liquid concentrate formula:

  • Read the label to see how much formula and boiled water to use.
  • Shake the tin or container well.
  • Wipe the top of the tin or container with hot water and soap and a clean dish cloth or towel.
  • If needed, open the tin or container with a disinfected can opener.
  • Measure the liquid by pouring it into a disinfected measuring cup.
  • Add the correct amount of boiled and cooled water.
  • Mix with a disinfected spoon.
  • Pour the formula into a disinfected bottle.
  • Use disinfected tongs to assemble the nipple parts on the bottle.
  • Tighten the ring without touching the nipple.

G) Preparing ready-to-use infant formula

1) Getting ready

Before preparing ready-to-use formula:

  • Wash your hands with soap and warm water.
  • Disinfect the counter areas.
  • Assemble the necessary disinfected tools and bottles.

Ready-to-use is the safest formula for babies at increased risk of infection. It is sterile until the container is opened.

2) Preparing ready-to-use infant formula

To prepare ready-to-use formula:

  • Shake the tin or container well.
  • Wipe the top of the tin or container with hot water and soap and a clean dish cloth or towel.
  • If needed, open the tin or container with a disinfected can opener.
  • Pour the liquid directly into a disinfected bottle.
  • Use disinfected tongs to assemble the bottle.
  • Tighten the ring without touching the nipple.

H) Storing infant formula

1) Storing prepared formula

Storing formula increases the risk of bacterial growth. It is best to use freshly prepared formula. If this is not possible, prepared formula stored in bottles should be:

  • Kept at the back of the refrigerator, where it is colder.
  • Thrown out after 24 hours.
  • Thrown out 2 hours after the baby has drunk from the bottle.

Do not store formula that was made with powder and with water that was cooler than 70°C (160°F).

Guidelines for storing expressed breast milk are different.

2) Storing formula tins and containers

All formula tins and containers should be stored in a cool, dry place (Seo 2018).

Opened powdered formula tins and containers should be:

  • Stored in a cool, dry place with the lid tightly closed.
  • Thrown out:
    • After being open for one month.
    • Before the expiry date.

Opened liquid concentrate and ready-to-use tins and containers should be covered and stored in the refrigerator for up to 48 hours or following the instructions on the label.

I) Infant formula temperature when feeding

We recommend that formula is given at body temperature. There is a small amount of research to support this (Dumm 2013; Eckburg 1987; Gonzales 1995; Holt 1962; Uygur 2019). Babies take in a lot of milk relative to their size and cold milk probably doesn’t feel as good as warm milk. This may be especially important for very small babies.

Always shake the milk and then test the temperature on the inside of your wrist. It should feel slightly warm and not hot.

1) Cooling infant formula

Formula that was prepared with hot water must be cooled before giving it to the baby. This can be done by placing the bottled milk in a bowl of cold water or placing the bottle in a refrigerator. Always test formula before use to ensure it is not too hot.

 2) Warming infant formula

Do not use a microwave to warm formula. It may have hot areas, causing burns in the baby’s mouth. Instead, place the bottle in a bowl of warm water.

When warming formula, do not let it stay warm for more than 15 minutes before the baby drinks it.

J) Automatic infant formula preparation machines

Formula preparation machines are not considered safe as:

  • The water may not be hot enough to kill bacteria present in powdered formula.
  • The machine may not delivery the right amount of water resulting in formula that is too rich or weak.
  • The machine may itself be contaminated with bacteria and other microbes, especially if it is not cleaned regularly.

References

Altazan AD, Gilmore LA, Guo J, et al. Unintentional error in formula preparation and its simulated impact on infant weight and adiposity. Pediatr Obes. 2019 Jul 26:e12564

Appleton J, Fowler C, Laws R, et al. Professional and non-professional sources of formula feeding advice for parents in the first six months. Matern Child Nutr. 2020 Jan 13:e12942 

Carletti C, Cattaneo A. Home preparation of powdered infant formula: is it safe? Acta Paediatr. 2008 Aug;97(8):1131-2
 
Cho TJ, Hwang JY, Kim HW, et al. Underestimated Risks of Infantile Infectious Disease from the Caregiver's Typical Handling Practices of Infant Formula. Sci Rep. 2019 Jul 5;9(1):9799
 
Dumm M, Hamms M, Sutton J, et al. NICU breast milk warming practices and the physiological effects of breast milk feeding temperatures on preterm infants. Adv Neonatal Care. 2013 Aug;13(4):279-87
 
Eckburg JJ, Bell EF, Rios GR, et al. Effects of formula temperature on postprandial thermogenesis and body temperature of premature infants. J Pediatr. 1987 Oct;111(4):588-92
 
Ellison RG, Greer BP, Burney JL, et al. Observations and Conversations: Home Preparation of Infant Formula Among a Sample of Low-Income Mothers in the Southeastern US. J Nutr Educ Behav. 2017 Jul - Aug;49(7):579-587.e1

Fossen Johnson S. Methemoglobinemia: Infants at risk. Curr Probl Pediatr Adolesc Health Care. 2019 Mar;49(3):57-67 

Gonzales I, Duryea EJ, Vasquez E, et al. Effect of enteral feeding temperature on feeding tolerance in preterm infants. Neonatal Netw. 1995 Apr;14(3):39-43
 
Herbold NH, Scott E. A pilot study describing infant formula preparation and feeding practices. Int J Environ Health Res. 2008 Dec;18(6):451-9
 
Holt LE Jr, Davies EA, Hassel Meyer EG, et al. A study of premature infants fed cold formula. J Pediatr. 1962 Oct;61:556-61
 
Hormann E. Reducing the risk for formula-fed infants: examining the guidelines. Birth. 2010 Mar;37(1):72-6
 
Labiner-Wolfe J, Fein SB, Shealy KR. Infant formula-handling education and safety. Pediatrics. 2008 Oct;122 Suppl 2:S85-90
 
Lakshman R, Ogilvie D, Ong KK. Mothers' experiences of bottle-feeding: a systematic review of qualitative and quantitative studies. Arch Dis Child. 2009 Aug;94(8):596-601
 
Levallois P, Barn P, Valcke M, et al. Public Health Consequences of Lead in Drinking Water. Curr Environ Health Rep. 2018 Jun;5(2):255-262
 
Malek L, Fowler H, Duffy G, et al. Informed choice or guessing game? Understanding caregivers' perceptions and use of infant formula labelling. Public Health Nutr. 2018 Nov 27:1-14
 
Redmond E, Griffith C, Riley S. Contamination of bottles used for feeding reconstituted powdered infant formula and implications for public health. Perspect Public Health. 2001 Mar;129(2):85-94
 
Seo CW, Hong S, Shin YK, et al. Physicochemical Properties of Liquid Infant Formula Stored at Different Temperatures. Korean J Food Sci Anim Resour. 2018 Oct;38(5):995-1007
 
Silano M, Paganin P, Davanzo R. Time for the 70°C water precautionary option in the home dilution of powdered infant formula. Italian Journal of Pediatrics. 2016;42:17
 
Uygur O, Yalaz M, Can N, et al. Preterm Infants May Better Tolerate Feeds at Temperatures Closer to Freshly Expressed Breast Milk: A Randomized Controlled Trial. Breastfeed Med. 2019 Apr;14(3):154-158
 
WHO/UNICEF. Safe preparation, storage and handling of powdered infant formula: guidelines. Geneva: World Health Organization; 2007