Oakland County, Michigan/Health/Information/Breast Milk Safety Storage

Breast Milk Safety Storage

Why is it important to collect and store breast milk safely?

Following safety guidelines can prevent contamination of pumped breast milk with germs and bacteria.  Your baby could get sick if he/she drinks breast milk that has been contaminated.

How should I collect breast milk safely?

  • Wash hands well with soap and water.
  • Wash all the collecting bottles and breast pump parts that touch your breasts or the milk.
  • Use hot, soapy water or a dishwasher to clean all collection bottles and breast pump parts. 
  • Steam bags may be used if hot water is not available.

How should I store breast milk?

  • Pump your milk into Bisphenol A (BPA)- free breast milk collection bottles or disposable bags designed for breast milk.  Seal containers tightly. 
  • Clearly label the milk with the date it was expressed. Always use the oldest milk first.
  • If you do not plan to use the milk within a few days, freeze it promptly in the coldest section of your freezer.  Do not place the bottle or bag against the wall of the freezer.
  • Store and/or freeze milk in 2 oz. “ 5 oz. portions.  Small amounts will thaw more quickly, and less milk will be wasted if baby does not eat it all.
  • Liquids expand when frozen.  Leave extra room at the top of the bottle/bag so it will not burst in the freezer.
  • You can continue to add small amounts of cooled breast milk to the same refrigerated container throughout the day.  Do not add warm milk to already cooled milk or frozen milk.  Doing so will warm or thaw the milk, making it unsafe.
  • Do not add fresh milk to already frozen milk within a storage container.  It is best not to mix the two.
  • If you are storing pumped milk "on the go," be sure to keep the breast milk in an insulated thermal bag or cooler with at least three frozen ice packs.  The temperature in the insulated bag or cooler should be 59°F or lower.  Pumped breast milk should be put into a refrigerator or freezer as soon as possible.

How do I safely rid breast milk of an odd color, odor, or taste?

  • It is normal for pumped milk to vary in color, consistency and scent depending on your diet.
  • Stored milk separates into layers.  Cream will rise to the top.  Gently swirl (with a clean, sanitized utensil) the warmed bottle to mix the milk layers before feeding baby.  Never use your finger to stir the milk.
  • Sometimes breast milk can have a soapy taste or odor.  This is due to a naturally occurring enzyme called lipase, which helps baby digest the fat content of the breast milk. 

How should I safely thaw breast milk? 

Use any process below to safely thaw breast milk.  Breast milk can be warmed to body temperature if preferred.

  • Thaw milk overnight in the refrigerator.
  • Place the sealed bottle or bag in a bowl of warm water for 20 minutes.
  • To defrost breast milk quickly, hold bottle under warm running water.
  • Avoid using the microwave oven to thaw or heat bottles of breast milk since microwaves do not heat liquids evenly.  Heat can also destroy the nutrient quality of breast milk.

Are there special considerations for donated breast milk?

  • Some women are able to produce extra amounts of breast milk and may consider donating to a breast milk bank to help another baby get the nutrients he/she needs. 
  • When pumping breast milk to donate to a bank, follow all breast milk storage safety guidelines to ensure that it is safe and another baby will be able to use it. 
  • Milk that is donated through a human breast milk bank is operated through the Human Milk Banking Association of North America (HMBANA).  HMBANA screens all breast milk donors.  The milk is thoroughly tested to ensure that it is safe for every baby receiving the milk.
  • Breast milk sharing sites that are not part of HMBANA do not screen or test donated breast milk.  Milk received from a sharing site may have high bacterial count that is not safe for your baby.

What are breast milk storage guidelines?


Room Temperature

Insulated Cooler Bag


Freezer Compartment of Refrigerator

Freezer Compartment of Refrigerator with Separate Door

Chest or Upright Deep Freezer

Freshly expressed breast milk6-8 hours  
up to 77° F
(up to 25° C)
24 hours
(-15-4° C)
5 days  
39° F
(4° C)

2 weeks

5° F

(-15° C)

3-6 months

0° F

(-18° C)

6-12 months

 -4° F

(-20° C)

Thawed breast milk Do not storeDo not store24 hoursNever re-freeze thawed milkNever re-freeze thawed milkNever re-freeze thawed milk

For additional information about cleanliness and to avoid spreading illness, visit the Oakland County Health Division - Hand Washing web page.