Breast Milk Storage: Freezing and Thawing Guidelines
By Lansinoh UK | Published: 2026-10-13
Category: How-to Guides
Follow these step-by-step breast milk storage guidelines to freeze, thaw, and warm milk safely, so every feed stays fresh and you waste less.
Quick answer
Freeze expressed breast milk as soon as possible after pumping, label it with the date, and use the oldest milk first. Thaw it in the fridge overnight or under cool running water, then warm it gently in a bowl of warm water. Never refreeze thawed milk or heat it in a microwave.
How long can breast milk be frozen?
Use these time limits as a guide, and always follow your midwife or health visitor’s advice if your baby was premature or has health concerns. Freshly expressed milk can stay at room temperature (up to 25°C) for up to 4 hours, in the fridge (0–4°C) for up to 4 days, and in a freezer compartment inside a fridge for up to 2 weeks. A freezer with a separate door keeps milk safe for up to 3 months, and a deep freeze (–18°C or colder) for up to 6 months. Store milk at the back of the fridge or freezer, not in the door, where the temperature fluctuates.
How to freeze breast milk
Pump directly into clean, sterilised containers or breast milk storage bags. Leave about 2.5 cm of space at the top because breast milk expands as it freezes. Write the date on the container or bag before you fill it—once frozen, labels can be hard to stick. Freeze milk in small portions (60–120 ml) so you thaw only what you need and waste less. If you add freshly pumped milk to already frozen milk, cool the fresh milk in the fridge first, then pour it over the frozen block. Never add warm milk directly to frozen milk.
How to thaw breast milk safely
The safest way to thaw breast milk is in the fridge overnight. If you need it sooner, hold the container under cool running water, then gradually increase the water temperature to warm. You can also place the container in a bowl of warm water. Never thaw or warm breast milk in a microwave or boiling water—high heat destroys some of the milk’s protective properties and creates hot spots that can burn your baby. Once thawed, use the milk within 24 hours if it was thawed in the fridge, or within 2 hours if thawed at room temperature. Do not refreeze thawed milk.
Warming frozen breast milk
Warm thawed or freshly expressed milk by standing the bottle or bag in a bowl of warm water. Test a few drops on the inside of your wrist before feeding—it should feel lukewarm, not hot. Swirl the milk gently to mix any separated cream back in; do not shake it vigorously. If your baby doesn’t finish the bottle, throw away the leftover milk within 2 hours of the feed starting. Never save unfinished milk for later.
Your step-by-step freezing and thawing routine
- 1. Label before you pump: Write the date on your storage bag or container before filling it. Once frozen, bags can be slippery and labels may not stick. Checkpoint: every container should have a clear date.
- 2. Pump and portion: Express milk into clean containers or bags. Aim for 60–120 ml per portion to reduce waste. Checkpoint: leave 2.5 cm of space at the top for expansion.
- 3. Cool and combine: If adding to already frozen milk, cool the fresh milk in the fridge first, then pour it over the frozen block. Mistake to avoid: never pour warm milk directly onto frozen milk.
- 4. Freeze promptly: Place containers at the back of the freezer, where the temperature is most stable. Use the oldest milk first. Checkpoint: keep a dated rotation so nothing gets lost.
- 5. Thaw in the fridge or under cool water: Move frozen milk to the fridge overnight, or hold it under cool running water if you need it sooner. Never use a microwave. Mistake to avoid: microwaving creates hot spots and damages milk.
- 6. Warm gently and test: Stand the bottle in a bowl of warm water, swirl gently, and test a few drops on your wrist. Checkpoint: milk should feel lukewarm, not hot.
- 7. Use within safe times: Use thawed milk within 24 hours if thawed in the fridge, or 2 hours if thawed at room temperature. Discard leftovers within 2 hours of a feed. Mistake to avoid: never refreeze thawed breast milk.
Products that make storage easier
- Manual Breast Pump: Lansinoh’s Manual Breast Pump provides a portable and convenient option for breastfeeding women who want to express discreetly and in comfort while on the move, as it does not require batteries or an electrical source. Designed for ease of use, a simple switch at the top of the handle enables you to switch between the ‘let down’ and ‘expression’ phases of breastfeeding. Because it needs no power, you can pump directly into storage containers wherever you are, then freeze the milk as soon as you get to a fridge or freezer.
- NEW Breast Pump Accessory Set: The Lansinoh Breast Pump Accessory Sets are a great way to stock up on replacement parts all in one go. The single set includes: 2 x White Valves, 1 x Diaphragm, 1 x Diaphragm Cap, 1 x Breast Cushion Body, 1 x 160ml Container, 1 Tubing Set suitable for single or double pumps, 1 x 25mm Breast Cushion, 1 x 30.5 Breast Cushion and 1 x Container Lid. A spare 160ml container and lid means you always have a clean, freezer-safe vessel ready for the next pump session.
- Replacement Wearable Pump Breast Cushions: Pump comfortably and efficiently with the right fitting breast cushion. These are available in 24mm & 27mm. Please note: for health protection & hygiene reasons, once opened, this product may not be returned. A correctly sized breast cushion helps you express more milk in less time, so you can build a freezer stash without discomfort.
