Formula feeding FAQs

We’ve answered your questions about formula feeding.

Can I heat bottles in the microwave?

No. Never warm up formula in a microwave. It may heat the feed unevenly and burn your baby’s mouth.

Will adding extra powder make my baby sleep longer?

No. Too much powder can make your baby constipated or dehydrated. Too little powder may not give your baby enough nourishment. It’s best to follow the instructions on the packet.

Is it possible to overfeed a formula-fed baby?

Yes. It can be easier to overfeed a bottle-fed baby than a breastfed baby, because it’s harder for bottle-fed babies to control the milk flow. It can also be easier to unintentionally pressure a baby to feed from the bottle than the breast.

Overfeeding can cause:

  • stomach problems such as bad wind, cramps, and frequent, sloppy, foul-smelling poo
  • belching
  • vomiting
  • irritability
  • sleep problems.

Try not to worry too much about this. You can avoid overfeeding your baby by:

  • getting to know the signs that your baby is hungry (instead of when they just want a cuddle)
  • getting to know your baby’s cues that they’ve had enough
  • avoiding trying to make them drink more than they want.

Talk to your health visitor if you have any concerns about how much formula your baby is drinking.

What if I need to make up a feed before going somewhere?

It’s best to make up feeds one at a time as your baby needs them as this helps avoid infection. Sometimes this isn’t possible, and you may need to take a feed out with you (for example, to a nursery).

If you’re using powered formula, prepare the feed at home and cool it for at least 1 hour in the back of the fridge. Take it out of the fridge just before you leave and carry it in a cool bag with an ice pack and use it within 4 hours. If you don’t have an ice pack or access to a fridge you should use the feed within 2 hours.

As a general rule, if made-up formula is stored:

  • in a fridge, use it within 24 hours
  • in a cool bag with an ice pack, use within 4 hours
  • at room temperature, use within 2 hours.

Some women prefer to use ready-to-feed liquid formula when they’re out and about because it’s more convenient. Just remember that your bottles still need to be sterilised and any unused formula should be thrown away if you can’t store it according to the instructions on the carton or bottle.

I think my baby is lactose intolerant. Should I start them on lactose-free formula?

It’s important to see your GP if your baby is having a reaction to formula milk. They may be lactose intolerant but it’s also possible they have a cow’s milk allergy. These problems need to be treated differently, so don’t make any changes to your baby’s diet until they’ve been seen by a doctor.


Find out more about feeding your baby

  • A photo of a mum breastfeeding her baby with bottles visible on the table in the foreground

    Combine feeding

    Combine feeding is when you offer your baby bottles of expressed breast milk or formula alongside breastfeeding. It’s sometimes called combination or mixed feeding, or partial breastfeeding.

  • A breast pump.


    Expressing milk means squeezing milk from your breast so you can store it and feed it to your baby later.

  • Dad bottle-feeding baby formula.

    Formula feeding

    Formula is man-made milk that is designed for babies and can be used in combination with, or instead of, breastfeeding. Formula feeding is perfectly safe, just make sure you take care every time you make a bottle.

  • 'FAQ' written in pink chalk on black board.

    Breastfeeding FAQs

    Here are some answers to common questions about breastfeeding.

  • Mum breastfeeding baby.

    Breastfeeding information and support

    Breast milk is a fantastic first food for your baby because it protects them from illness. Breastfeeding has lots of benefits for you, too.

  • Mum breastfeeding baby.

    Feeding your baby

    Feeding can be a lovely time to get to know your baby and to bond. At the start you’re going to be doing a lot of feeding.


NHS Choices. Your pregnancy week by week. (Page last reviewed: 22/07/2014. Next review due: 22/07/2016)

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    Last reviewed on May 9th, 2019. Next review date May 9th, 2022.

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    Please note that these comments are monitored but not answered by Tommy’s. Please call your GP or maternity unit if you have concerns about your health or your baby’s health.

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