GENERAL STORAGE TIPS

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• Label all milk with the last date expressed before storing. If your milk may be given to your baby in a group setting such as daycare or pre-school, add your baby’s name to the label. 

• Store milk in different amounts ranging from one to four ounces (30 to 120 mls) to avoid waste. 

• Refrigerate or chill your milk as soon as you can after expressing it. 
  The Academy of Breastfeeding Medicine Human Milk Storage protocol (2017) recommends chilling fresh milk in the refrigerator before adding it to previously expressed milk. Combining or pooling  expressed milk in a single storage container over a 24 hour period minimizes variation in nutritional content and simplifies milk handling without increasing bacterial growth.  

• Whenever possible, give your baby refrigerated milk before frozen milk. Some nutrients are lost when the milk is frozen. 

• Generally start with the oldest refrigerated milk, and then use the oldest frozen milk if needed.

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STORAGE CONTAINERS

 

Bottles

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• Use glass or hard-sided plastic containers with well-fitting tops.

• Avoid plastic containers made with the chemical bisphenol A (BPA) or bisphenol S (BPS). A safe alternative is polypropylene. You can avoid the risks of plastic completely by using glass.

• Wash containers in hot, soapy water, rinse well, and allow to air-dry before use or wash and dry in a dishwasher.

• Containers should not be filled to the top. Leave an inch (2.5 cm) of space to allow the milk to expand as it freezes.

 

Bags

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• Use only freezer milk bags that are designed for storing human milk.
  Experts do not recommend using disposable bottle liners or plastic bags that are not designed for storing milk. They are less strong and tend to leak.  The risk of contamination is greater. Some types of plastic may destroy nutrients in milk.

• Squeeze out the air at the top before sealing, and allow about an inch (2.5 cm) of space for the milk to expand when frozen.

• Stand or lay the bags in another container at the back of the refrigerator shelf or in the back of the freezer where the temperature will remain the most consistently cold.

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Warming Refrigerated Milk

​While many infants may be content drinking room temperature milk, some may have a preference for warmer milk. Experts recommend to warm milk slowly in lukewarm water to protect the fat content and nutrients.

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Thawing From Frozen

​There are several safe ways to thaw frozen milk:

• Thaw in the refrigerator overnight

• Run warm water over the sealed frozen container of milk

• Place frozen container in cup of warm water

 

Avoid boiling and do not microwave human milk. These methods will cause loss of nutritional properties of the milk. Microwaving can heat the milk unevenly, producing hot spots that could cause burns  (ABM, 2017).

 

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COMMON QUESTIONS

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Why does my stored milk smell or taste different from fresh milk?

Expressed human milk may undergo odour changes when stored. Parents sometimes describe expressed or defrosted milk as smelling odd — metallic, soapy, or even rancid. The reasons are not well understood, but it may be due to the breakdown of milk fats over time. If stored properly, this milk is safe and most babies will drink it. For more information see: Milk issues – Smell of Stored Human Milk.

 

Why is my milk separating?

Human milk naturally separates into a milk layer and an upper cream layer when it is stored. This is normal. Shake or swirl the milk to combine the cream prior to feeding.

 

Is it safe to refreeze my milk after thawing?

Previously frozen milk that has been thawed can be kept in the refrigerator for up to 24 hours (Lawrence & Lawrence, 2010). There is  little research on the safety of refreezing human milk, but it may introduce further breakdown of nutrients and increase the risk of bacterial growth. At this time, the accepted practice is not to refreeze thawed milk.

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Are there guidelines for chilling  milk when there is no refrigerator access?

The Academy of Breastfeeding Medicine Human Milk Storage protocol (2017) states that there have not been many studies examining this. The ABM suggests that human milk stored in a small cooler with an ice pack could be safe for up to 24 hours. Aim to transfer your milk to a refrigerator or freezer for reliable storage temperatures as soon as possible.

If a cooler with ice pack is not available, researchers have suggested that the container with expressed milk can be immersed/surrounded by a vessel with cold water.The findings from an Nigerian study suggested that storage of breast milk either at room temperature or immersed in a container of water appeared to be safe for up to 9 hours of storage in a tropical environment (Ukegbu, PO et al,2013).

 

Can I reuse previously fed milk if my baby does not finish?

If your baby does not finish the bottle during a feed, experts recommend using the remaining milk within two hours. Discard any milk left after this time frame (ABM, 2017). Storing milk in smaller quantities can help reduce waste if your baby does not finish the bottle.

 

Is there anything that I can do with milk kept beyond the recommended storage guidelines?

Milk kept beyond the recommended storage guidelines may be used for external use. Some parents use it for skin baths or even making soap. However, there is no guidance or research on these practices.

Are human milk storage guidelines different for a refrigerator freezer and a deep freezer?

The storage guidelines for all types of  freezers are the same. The Center for Disease Control states that storage guidelines depend on the temperature of the freezer, not the type of freezer. Storage guidelines specify freezing at temperatures of 0° F (-17.8° C) or less. If your refrigerator freezer meets these temperatures, then the guideline applies.  More information here.

 

Is it safe to store my milk in a shared refrigerator?

Expressed milk can be kept in a common refrigerator at the workplace or in a day care center. The US Centers for Disease Control and the US Occupational Safety and Health Administration agree that human milk is not among the body fluids that require special handling or storage in a separate container (CDC, 2023).

 

I have thrush. Is my milk safe?  

According to the Academy of Breastfeeding Medicine and several other sources, there is no need to discard milk that was pumped during a mother’s presumed thrush infection. For more details and references see the our article on thrush.

If your baby has thrush in their mouth, research suggests that thrush is not automatically passed along to you through breastfeeding. Therefore, continued breastfeeding is not a concern. 

 

Can I mix my milk with formula?

Experts recommend that you feed human milk separately from any formula to maximise the benefits of human milk. For more details see this article.

 

Do I need a freezer stash?  

Human milk stored in the refrigerator or freezer continues to provide excellent nutrition and other health support. Offering the freshest milk available may have health advantages. Consider how much milk you need in storage. This will vary depending on your own circumstances. While it can be reassuring to have some amount as backup, consider making just what your baby needs in your situation. Many mothers who are separated from their children after returning to work or school express and leave milk for the next day. They may have a small freezer backup or stash for emergencies only.  See this article.

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Additional Resources

LLL Canada, Storing Human Milk

LLL USA, Storing Human Milk 

Nancy Mohrbacher, Why Do Milk Storage Guidelines Differ?

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REFERENCES

Academy of Breastfeeding Medicine. (2017) Clinical Protocol Number #8: Human Milk Storage Information for Home Use for Healthy Full Term Infants.  Breastfeeding Medicine, 12(7), 390-395.

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Centers for Disease Control and Prevention (CDC). (2023). Breast Milk Storage and Preparation Retrieved from https://www.cdc.gov/breastfeeding/breast-milk-preparation-and-storage/handling-breastmilk.html

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Centers for Disease Control and Prevention (CDC). (2023). Breast Milk Storage Questions and Answers Retrieved from https://www.cdc.gov/breastfeeding/php/guidelines-recommendations/faqs.html

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Jimenez et al. Mammary candidiasis: A medical condition without scientific evidence? PLoS ONE, 12(7): e0181071,2017,https://eadn-wc01-5994650.nxedge.io/wp-content/uploads/2021/08/JimenezetalCandidiasnotcauseofpain.pdf 

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Lawrence, R.A. & Lawrence, R.M. (2010). Breastfeeding: A Guide for the Medical Profession (7th ed.). Elsevier Mosby, Philadelphia

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Morbacher, Nancy (2020). Breastfeeding Answers (2nd ed.). Arlington Heights, IL: Nancy Morbacher Solutions, Inc., 726-31. 

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Newman, J. & Pitman, T. (2014). Dr. Jack Newman’s Guide to Breastfeeding, Revised Edition. UK: Pinter & Martin, Ltd.

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Ukegbu, PO et al,(2013)  Bacterial Load in Expressed and Stored Breast Milk of Lactating Mothers in Abia State, Nigeria, African Journal of Food, Agriculture, Nutrition and Development (ajol.info)<https://www.ajol.info/index.php/ajfand/article/view/94614>

 

*This page was generously supplied by La Leche League International