Can You Refrigerate Leftover Breastmilk from the Bottle?
No, you should discard leftover breast milk from a bottle after a feeding session rather than refrigerating it for later use.
Storage Guidelines for Expressed Breast Milk
The key distinction here is between unfed expressed milk (milk that has been expressed but never offered to the baby) versus leftover milk (milk that the baby has partially consumed from a bottle).
Unfed Expressed Milk Storage
- Refrigerate unfed expressed breast milk for up to 72 hours at 4-10°C 1
- Store at room temperature (15-25°C) for up to 4 hours 1
- Freeze at -20°C for up to 1 month 1
- These durations apply only to milk that has not been offered to the infant 1, 2
Leftover Milk After Feeding
While research suggests that leftover milk (milk the baby has started drinking from) may remain bacteriologically stable when refrigerated at 4°C for up to 6 days 3, current guidelines do not support refrigerating and reusing leftover milk. The concern is bacterial contamination from the infant's saliva introduced during feeding 3.
The safest practice is to discard any milk remaining in the bottle after a feeding session 4, 5. This prevents potential bacterial growth from oral flora that enters the milk during feeding.
Important Caveats
- Once thawed milk should be used within 6 hours and never refrozen 1, 4
- The research on leftover milk storage is limited to pilot studies with small sample sizes 3, and investigators explicitly state that "storage guidelines should not be revised until more research is performed" 3
- Factors like milk value, convenience, and cost influence mothers' practices, sometimes leading to deviations from recommendations 5, but safety should remain the priority
Practical Approach
To minimize waste while maintaining safety:
- Offer smaller volumes per feeding to reduce leftover amounts
- Store expressed milk in smaller portions (2-4 oz containers) so you only thaw/warm what the baby will likely consume
- Label all stored milk with expression date and time to track storage duration 5