Breast Milk Bottles FAQs

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Cleaning / Sanitizing

  • How do I clean the breast milk bottles?
    • Cleaning
      1. Prior to first use, bring water to boil then place lids & bottles in boiling water for 10 minutes.
      2. For regular cleaning, all components may be washed on top rack of dishwasher.  Labeling lids and breast milk bottles may be sanitized in boiling water for 10 minutes.  To hand wash, rinse in cool water to remove breast milk, wash in warm soapy water and rinse with clear water.  Air dry in clean area and store when not in use.  Do NOT store wet or damp parts.  Labeling lids and breast milk bottles may also be sanitized using a Quick Clean Micro-Steam bag.
      • Always test temperature of breast milk before feeding to your baby.
      • Always inspect the bottle, nipple and other components before and after each use.
      • To prevent possible choking hazard, test strength of nipple by pulling on bulb portion. If nipples appear cracked or torn, discontinue use immediately.
      • Infants must not be bottle fed without adult supervision.
      • Do not allow child to walk or run with bottle.
      • Do not let child take bottle to bed or self-feed for long periods of time.
      • Do not attempt to enlarge the nipple hole.
      • Nipples should not be used as pacifiers.
      • IMPORTANT:  Plastic bottles and component parts become brittle when frozen and may break when dropped.  Also, bottles and component parts may become damaged if mishandled, e.g. dropped, over-tightened, or knocked over.  Take appropriate care in handling bottles and components.  Do not use the breast milk if bottles or components become damaged.



  • Can bottle liners be used with Medela breast milk bottles?
    • Medela does not suggest the use of bottle liners as anything placed into the bottle can interfere with the valve assembly causing lack of suction.  If you wish to use a bottle liner, pump into Medela bottles and then pour the collected breast milk into the bottle liner.


  • What are the breast milk bottles made out of?
    • Medela breast milk bottles are made of FDA food contact grade polypropylene.  Medela bottles are BPA-Free and designed for safe feeding and long-term storage of breast milk.

      Polypropylene has a recycle number of 5 or PP stamped into the plastic item.  Medela only uses new, virgin materials in manufacturing of all products.

Misc. Questions & Answers

  • What are the ages for the slow and medium flow nipples?
    • Each silicone nipple is stamped with an “S” for Slow-flow or an “M” for Medium-flow. 

      Wide base slow flow 0-4 months.

      Wide base medium flow 4-12 months.

  • How do I store my breast milk?
      • It is normal for pumped milk to vary in color and consistency depending on your diet. Stored milk will separate into layers and the cream will rise to the top. Gently swirl (don’t shake) the bottle to mix the milk layers.
      • Avoid adding freshly pumped milk to already cooled milk.  You can add small amounts of cooled breast milk to the same refrigerated container throughout the day.
      • Pumped milk may be added to frozen milk provided it is first chilled and the quantity is less than what is frozen.
      • Store your milk in Medela’s BPA-free breast milk collection bottles or in storage bags specifically designed for breast milk, such as Medela’s Pump & Save bags.
      • Freeze milk in two (2) to four (4) ounce portions. Small amounts thaw more quickly. You will waste less milk this way. Be sure to leave some extra room at the top of the container so the bottle or bag will not overflow when freezing or thawing.
      • Seal containers tightly. Write the date on a piece of tape and place on the bag or bottle. Use the oldest milk first.
      • If you do not plan to use the milk within a few days, freeze it right away in the coldest section of your freezer.