Why You Must Never Add Extra Water To Breastmilk or Formula

Why You Must Never Add Extra Water To Breastmilk or Formula

Before supermarket price-wars drove the price of milk down to just a couple of dollars, your mother might have added a little water to the carton to make the last of the milk stretch until pay day.

However, what is okay for your morning cereal can have devastating health impacts if applied to your baby’s primary food source.

When your baby directly feeds from your breast, the milk he receives is perfectly balanced for his needs at that moment. The rich balance of nutrients, immune factors, fats and fluids is biologically produced without you having to do a thing.

That same balance needs to be maintained when you bottle feed your baby – it’s vital to their wellbeing.

Babies do not need bottles of boiled water — they naturally quench their thirst with breastmilk or formula. Despite the old wives’ tales, a little boiled water doesn’t cure colic and won’t help your baby burp. In fact, there are reasons to delay introducing water until your baby learns to drink from a cup after she starts solids.

Water, though vital to life, also has the power to kill. A condition known as Hyponatremia or “water intoxication” occurs when too much water is consumed, upsetting the fine balance of salts in the body. While an older child or adult would have to consume extreme amounts for this to occur, babies are especially vulnerable due to the size of their body.

Just recently, a baby girl died in the US, after her parents’ bottle fed her breastmilk that had been diluted with water.

If your baby is partly or fully bottle fed, here are four important things you need to know:

#1: Expressed Breastmilk Should Not Be Mixed With Formula

When you pump or hand express your breastmilk, it can be used immediately or combined with other breastmilk you have collected and stored in the fridge or freezer. It is important not to mix your expressed breastmilk (EBM) with infant formula, water or anything else.

The reason not to mix formula with breastmilk is a very good one. We recommend first giving expressed breastmilk and then any formula, separately. This way, the valuable, nutritious breastmilk is not wasted if not all the feed is taken. Of course, the baby fills up on breastmilk first, meaning he’ll get the most nutrition from a feed.

If you’d like to see what’s in breastmilk compared to what’s in formula, check out this link.

#2: Using Other Mother’s Breastmilk

Some Australian hospitals have milk banks, which are facilities that collect donated breast milk. They pasteurise it and make it available to their most vulnerable patients – premature or sick babies in the Neonatal Intensive Care Unit (NICU), whose mothers are unable to supply enough breastmilk to meet their baby’s needs.

Informal milk sharing is a privately arranged gift of milk from one mother to another, organised most commonly through social media groups such as Eats On Feets or Human Milk For Human Babies. Although unregulated, these mothers share a belief in the importance of breastmilk and offer excess or intentionally-collected milk to babies who have short or long term barriers to being fed exclusively by their mothers.

In some countries, buying and selling human milk as a commodity is a growing business. Adults, as well as infants, are consuming milk expressed and sold by the litre. Celebrity parents like Elton John and his partner David Furnish are high profile examples of gay parents happy to buy what they cannot provide naturally. It’s a growth industry.

But the buying or selling of human milk is illegal in Australia – and for good reasons! Researchers from the Nationwide Children’s Hospital in Columbus, Ohio counted more than 55,000 ad postings to buy or sell breast milk in 2014, up from 11,000 in 2011. Alarmingly, some 10% of samples of breastmilk bought online also contained cows’ milk, according to a study recently published in the journal Paediatrics.

#3: Always Use Only As Directed

For babies who are formula fed, it is very important to follow the instructions carefully when preparing feeds. Always use the scoop from that brand, as they may vary in sizes, and carefully count the scoops. If you lose count – stop and start again. Always boil the water freshly for each mix. The milk powder is not sterile and it’s the heat of the water which makes it safe to drink. As per World Health Organisation guidelines for formula preparation, it should never be cooler than 70 degrees Celcius when you mix it. Cool to feeding temperature after you thoroughly mix the powder and water. Always use within 30 minutes of mixing.

It is imperative that you boil the water first, then cool it to drinking temperature, in order to kill any bacteria. Not doing so puts your baby at risk of infection — and any city around the world can have bacteria outbreaks. Some years ago, this happened in Sydney, Australia and everyone, including adults, had to boil water before use. Babies are especially vulnerable with weaker immune systems. Please see the World Health Organization’s official formula preparation guidelines for more information.

#4: Specialty Baby Water – Not So Special

You might be surprised to find water bottled just for babies on your supermarket shelves, ready to use, teat and all. While this might seem like to ultimate in convenience, these products are not appropriate as drinks for babies under six months and are not necessary as drinks for older babies (who do not need drinking water boiled in Australia). This product may not be suitable for mixing and heating formula according to the World Health Organisation guidelines.

Learn more about expressing breastmilk in our article here.

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Yvette O'Dowd has been a breastfeeding counsellor and educator since 1992. She has three adult children and a two year old granddaughter - the best sort of bonus baby! Yvette runs a popular natural parenting network, is a babywearing educator, and runs antenatal breastfeeding classes for parents expecting twins and more! She is a keen photographer and scrap-booker and a keeper of a fairy garden.


  1. Us parents now a days are so confused on how any of us are alive. With all these bs articles. Most are helpful but you really need to take advice with a grain of salt. That’s just my opinion.

    1. Just because you survived, doesn’t mean the science is flawed. People use to smoke cigarettes and have no car seat to restrain their little ones. That doesn’t mean it’s safe, we just know better now.

    2. Not sure what part of the article you feel is BS. I live in the metro Detroit area where the baby recently died due to parents watering down the breast milk. Information like this apparently is VERY necessary. And just because we “survived” does not necessarily mean we survived as well as we could have with some of the new information we have today. Look at al the allergies or digestive issues, what about autoimmune disorders we are seeing in adults today? So many of these things would not be so prevelant had we known then what we know now.

  2. In some rare cases, there may be harmful bacteria an infant baby milk powder as this product is not sterile. The UK’S NHS advocated mixing a powdered formula feed with freshly boiled tap water which is over 70 degrees in order to kill any harmful pathogens that could make a baby sick. Shop bought bottled water should not to used either as many mineral waters have a salt/ sodium/ sulphate content that is too high for babies systems to process. If bottled water is the only option in an emergency then select the brand with the lowest levels of these elements. Filtered water is not sterile and requires boiling before use. For more detailed info please read in full http://www.nhs.uk/start4life/documents/…/start4life_guide_to_bottle_feeding.pdf
    Or google Bottle feeding advice – Pregnancy and baby guide – NHS Choices

  3. Hi.. I’m a mum of 3, youngest is only 4 months.. I agree you shouldn’t water breast milk down but that’s pretty obvious, & yes make formulas up how it says but use within 30mins part on here is different to my formula, mine says 2 hours.. Some babies take longer than 30 mins to feed lol & you kinda have to wonder what’s in that one if it goes off that quick.
    As for giving baby water, babies don’t need the extra water if on breast milk but when only having formula I and a lot of other mums find that it can make baby struggle filling a nappy at times. My son is fine for a few days but then won’t fill his nappy and is grumpy so I give him just 1 or 2 fl.oz of boiled water (cooled) & it helps him go again. When he goes fully onto solids this might have to increase up to every day or every other day but a few fl.oz here and there doesn’t hurt & in my opinion would do less damage than being badly constipated.
    It should be pretty obvious to people not to ply their young babies with lots of water etc though, makes you wonder about people sometimes.

    Now days there is too much you can’t have this and can’t have that, especially while pregnant, maybe that’s why so many kids can’t eat certain foods etc and are always ill, they all have poor immune systems because of it. There’s being cautious & there’s being over the top cautious.
    I can have the same illness as others & not take any meds & still be better in a quarter of the time it takes them.. I gave my kids good antibodies & let them play & get dirty etc & develop their own & they too are the same way.

  4. This article made me pitch 60 ml of precious breast milk because it fell over in water to warn it and some got in. The headline sucks. Long term adding of water is bad but the headline reads that water and ebm should never be mixed. Is new parents are paranoid enoug already without these sensationalised headlines. It’s important for people to know but choose your words and explain the exact situation in the first few
    Paragraphs. These parents must have mixed water in over MANY feeds!!

    1. I fully agree. We prepared mashed carrots for our 5m 3w baby, but we used vapour carrots instead of boiled carrots and it came too much dry (idiot I know, but we are just starting and learning..)
      I wanted to add 1 spoon of water, but my wife refused claiming it is dangerous for the baby, pointing me to this article!
      Can the author please specific that we are speaking of long term effects of missing vital nutrients from milk and not that water is “toxic”..

    2. Thanks for clearing that up, I added a little water because bag busted and that’s only bag had, I didn’t know you were not suppose to not add water . Which I don’t normally only did cause bag busted ,last bag and my daughter didn’t get off wk for another hour . : (

  5. Diluting breast milk with anything is bad. We aren’t talking a little bit of water got splashed in but actually diluting it with intentions of stretching it out to avoid formula use. Which a lot of parents do. It is unsafe.
    Being paranoid about a splash is a personal problem not the fault of the author of this article.

    Also the health issues in most countries are contributed to the over usage of antibiotics in humans and farm animals which we then ingest. Also the amount of pesticides we ingest with produce.. Do some research before spouting off at the author. Look up over use of antibiotic and side effects of pesticides. Look up the population growth a in major countries over the decades and how many deaths actually occurred. Just because you didn’t know about the deaths doesn’t mean they never occurred but in our technology driven world today news is faster and more wise spread than in the 1950s. Ignorant talk only multiplies into ignorant lessons. Educate yourself before you make rash statements.

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