How Long Do Sterilised Bottles Stay Sterile?

You've washed and sterilised the bottles. Now you're wondering: how long do they actually stay sterile? Can you do a batch at the start of the day and use them throughout, or does the clock start immediately? 

Here's the clear answer. 

How long does sterilisation last? 

A sterilised bottle stays sterile for up to 24 hours – but only if it's stored correctly. The moment you expose the inside of a sterilised bottle to open air, the sterility begins to degrade. Bacteria and particles from the environment start to settle on surfaces immediately. 

In practice, if you: 

• Keep the bottle fully assembled (teat, ring, and cap all in place) immediately after sterilising
• Store it upright in a sealed steriliser, a sterile container, or sealed in the steriliser with the lid on
• Don't leave it open on a drying rack or counter surface

...the bottle will remain suitably sterile for up to 24 hours. 

The best way to store sterilised bottles 

In a sealed steriliser

The simplest option. Many electric steam sterilisers have a sealed lid that maintains sterility inside the unit for 24 hours. You sterilise a batch, leave the lid on, and take bottles out as needed. 

In a Bebello Washer, the parts remain sterile for 72 hours thanks to the protected HEPA-filtered environment.

Fully assembled in the fridge

Assembling bottles immediately after sterilising (teat, collar, cap) and storing them in the fridge is a reliable option. The cold slows any bacterial growth, and the sealed bottle prevents recontamination. 

In a sterile container or storage bag

If you're on the go, sterile storage bags or containers let you transport pre-sterilised bottles without recontaminating them. Useful for hospital stays or longer outings. 

What not to do

Leave sterilised bottles open on a drying rack, upturned on a clean tea towel, or with teats or caps removed. All of these reintroduce bacteria within a short time. 

Does the 24-hour rule start from sterilising or from opening? 

From sterilising. Whether you open the steriliser to take one bottle out five minutes later or four hours later, the 24-hour clock started when the cycle finished. If you've had bottles sitting in a sealed steriliser for 23 hours, they're still fine. At 25 hours, sterilise again before use. 

If you open the steriliser, handle the bottles, and then put them back, the sterility is compromised regardless of time elapsed – you've introduced bacteria from your hands and the environment. 

What about bottles used at night? 

For night feeds, many parents find it easiest to:  

• Prepare a flask of hot water (at least 70°C, to kill any formula-related bacteria) before bed.
• Keep a sealed batch of sterilised bottles in the steriliser overnight
• Assemble the night feed bottle just before use – takes 30 seconds, avoids having ready-made formula sitting overnight
• Pre-made formula should not be left at room temperature for more than 2 hours. If you're making feeds ahead, store them in the fridge and warm just before use. 

Batch sterilising a full day's supply at once is much easier with a machine that holds 8 bottles per cycle. The Bebello 4-in-1 handles the whole process – wash, sterilise, and dry – in one go. 

Frequently asked questions 

Can you sterilise bottles in advance and use them the next day? 

Yes, as long as they're stored correctly (sealed, assembled) and used within 24 hours of sterilising. 

Do sterilised bottles need to be refrigerated? 

Not necessarily – a sealed steriliser at room temperature maintains sterility for 24 hours. Refrigerating assembled bottles is an additional option for peace of mind. 

What if I'm not sure how long a bottle has been sterilised? 

When in doubt, sterilise again. It takes minutes and is always the safe choice. 

Does the 24-hour rule apply to breast pump parts too? 

Yes – the same principles apply to any sterilised feeding equipment.