Collecting leaked milk

Can I collect the milk leaking from one breast while I breastfeed with the other?

Milk that leaks from one breast while mothers breastfeed with the other can be collected in a container placed under the breast. That container may be a cup or a commercial product sold for that purpose or mothers may want to use a constant-suction pump. The milk that leaks during or between feeds can be collected in a breast shell or other container placed inside a bra. Leaked milk may contain less fat than other breast milk, so it should not be fed to very small babies. If it’s collected in a container held inside a bra for extended periods, there’s a greater risk of contamination. That may pose a risk for very premature or sick babies.

A) Tools to collect leaked milk

Many mothers find that while they are breastfeeding with one breast they leak milk from the other. They may also leak when not breastfeeding. Leaked milk is good for use as a milk supplement and collecting it can be less work than expressing.

This milk can be collected in a:

  • Container held under the nipple. This may be a:
    • Cup
    • Commercial collection container
  • Container placed inside the bra
  • Constant-suction pump

A number of commercial products are available for collecting leaked milk. Any device should be practical, comfortable, and not leave red rings or areas on your breast.

Leaked milk should be properly stored as soon as possible after collecting. Containers placed in the bra will keep leaked milk especially warm next to the body, increasing the risk of contamination with bacteria.

B) When not to use leaked milk

Leaked milk may contain slightly less fat than other breast milk and should not be fed to very small babies who may struggle to grow well (Lucas 1978). If this is your situation, you may want to save this milk to use once the baby is bigger. 

Milk that is not properly stored may pose a risk to a very premature or sick baby who has a weaker immune system than a term baby. 


Lucas A, Gibbs JA, Baum JD. The biology of human drip breast milk. Early Hum Dev. 1978 Dec;2(4):351-61