Can You Reheat Baby Formula?

The World Health Organization suggests that babies should be exclusively breastfed for the first 6 months of life. However, some mothers may choose to use infant formula due to breastfeeding difficulties or health concerns.

Baby formula is a manufactured food designed to mimic breast milk and can be used to partially or completely replace breastfeeding for babies up to 1-year-old.

Routine formulas are made for healthy, full-term infants and come in various types, such as cow’s milk-based, goat’s milk-based, and plant-based. They vary in terms of nutrition, calories, taste, digestion, and cost. Let’s take a closer look at the various types of baby formula.

The majority of infant formulas are primarily based on cow’s milk as a source of protein. Bovine milk contains higher levels of fat, minerals, and protein than human breast milk. It contains natural sugar lactose. Cow’s milk is skimmed and diluted to more closely mimic the composition of human breast milk for easier digestion for your baby. These formulas also include added vegetable oils, vitamins, minerals, and iron, making them suitable for most healthy full-term infants.

Your baby may develop an allergy to cow’s milk, one of the infants' most common food allergies. Additionally, lactose intolerance may occur, when the body struggles to digest lactose.

A2 milk options are becoming popular with families because they’re gentle and tasty. Formulas based on whole goat milk protein or skimmed milk naturally have less lactose than cow’s milk, and smaller fat globules thus being easier on your child’s tummy.

These formulas offer an excellent alternative to cow milk-based baby formulas providing the same nutrition. They are a good choice for those with cow’s milk allergies.

European baby formulas are keeping up with the times to suit all families. Vegan baby formulas are made from clean, minimally processed plant ingredients, providing complete nutrition just like traditional formulas.

Vegan options are great for addressing special medical needs or lifestyle preferences. It’s a good idea to contact your pediatrician to make the right choice for your baby.

Soy-based formulas may help infants with cow-milk allergy and lactose digestion problems. The possible harm from the plant estrogens in these formulas is still debated.

Specialty formulas are designed for infants facing medical or dietary challenges. These formulas may be prescribed by a doctor and include hypoallergenic formulas, condition-specific formulas for diseases like Phenylketonuria or lacking certain amino acids, formulas with extra nutrients and calories to meet the unique needs of premature infants, and amino acid-based formulas suitable for infants with severe milk allergies or certain medical conditions.

There are three forms of infant formula:

1. Powdered formula: You need to mix it with water before feeding.

Powdered baby formula is the favored choice of many parents, as it is budget-friendly and has a longer shelf life in a canister. You measure the required water and add the appropriate amount of powder as instructed on the formula packaging.

2. Liquid concentrate formula: You need to mix it with an equal amount of water before feeding.

The liquid formula is like powdered formula but in sterile liquid form, packaged in cans or bottles. You mix it with water before use, while keeping unused, unmixed formula covered in the fridge for up to 48 hours. It offers a middle ground between powdered and ready-to-feed formulas in terms of convenience and cost.

3. Ready-to-feed: No mixing is required, it’s ready to use.

The ready-to-feed formula is gaining popularity for its convenience. It comes in pre-prepared single-use bottles, so you don’t need to add water or mix anything. This makes it a comfortable choice for baby feeding, especially when on the go.

Starting with the basics of safe formula preparation and storage is essential for keeping your baby healthy and happy.

● Make sure the formula isn’t expired by checking the date on the container.

● Good hygiene is crucial. Wash and dry your hands and clean the area where you make the formula properly because babies can get sick easily.

● Cleaning bottles with soap and water removes germs but sterilizing them goes the extra mile. Make sure to sterilize bottles, nipples, caps, and rings before using them for the first time. You can do this by boiling them in water for five minutes or using a bottle sterilizer that uses steam.

● After the first use, usually, there’s no need for sterilization. Just wash them with hot, soapy water using brushes, or a dishwasher. However, if your baby is less than 3 months old, born prematurely, or has a weak immune system, ask your pediatrician about continuing to sterilize the bottles.

To find out more details on safe cleaning, visit the CDC’s webpage.

When preparing a formula, always stick to the container’s instructions for the correct formula-to-water ratio, unless advised otherwise by your pediatrician or pediatric dietitian. Too much water means fewer nutrients for your baby while too little can cause digestion issues or not having enough fluids.

Remember to measure water first and then add the powdered or concentrated liquid formula.

For safety, use freshly boiled tap water at a temperature of 70˚C or above. This helps prevent any rare but dangerous bacteria. Make sure to take extra precautions if your baby belongs to the risk group mentioned above to reduce the risk of illness from Cronobacter sometimes found in powdered formula.

The choice of water for preparing infant formula can be a topic of debate.

According to the CDC, clean tap water that contains fluoride is generally recommended, as it is essential for developing your baby's teeth and remains in the water even after filtration. Families in Europe, America, and Canada are often in disagreement about the addition of fluoride to the water used in making baby formula. Also, it is advisable to consult your pediatrician for their opinion on fluoride.

The question of bottled water is a bit controversial. Cleveland Clinic advises against consuming bottled water, as distilled, purified, deionized, or demineralized water lacks fluoride and isn’t sterile unless it’s specifically labeled as baby or nursery water. 

The NHS also advises against bottled water, citing concerns about its sterility and salt and sulfate levels. CDC considers it safe for baby formula preparation, particularly, when tap water isn’t safe.

Too much fluoride can cause white lines on teeth (fluorosis). So if your baby drinks only concentrated or powdered formula, the CDC suggests switching between tap water with fluoride and bottled water with less fluoride.

Fresh is Best: Make formula when your baby needs it to avoid infection and to keep them healthy.

Room Temperature: Any prepared, unused formula can stay out for up to 2 hours, considering that bacteria multiply rapidly at room temperature. You have the option to either give it to your baby or store it in the refrigerator.

Keep it Cool: For open unused ready-to-feed formula, use it within 48 hours if it’s in the fridge.

The premade powdered/liquid concentrate unused formula is good for 24 hours in the fridge.

Overnight Hack: For overnight feeds, you can prepare bottles before bedtime, pop them in the fridge, and use them within 24 hours.

Discard Old Formula!: Once feeding begins, finish the bottle within 1 hour. Don’t save it for later, as bacteria from your little one’s saliva can grow.

It depends. Generally, you don’t have to warm your baby’s formula, as it’s perfectly acceptable to feed them cold or at room temperature. However, if you prefer to warm it, you should follow the guidelines for safe preparation, usage, and storage discussed above. Let’s consider this logically.  

If you have been following the safe handling and storage guidelines we’ve outlined, you can safely reheat pre-made formula bottles. This means that if an unused bottle of premade powdered/liquid concentrate formula is refrigerated, you have a 24-hour window to reheat it. 

If you have opened but unused store-bought liquid formula, it is safe to reheat the bottle within 48 hours while storing it in the refrigerator.

It’s recommended to reheat the baby formula only once. After that, feed your baby within 2 hours and discard any remaining formula. Repeated heating can cause nutrients to break down and bacteria to grow. 

No, you should use it within one hour after starting feeding and discard any remaining formula. Do not reheat it, as reheating can promote bacterial growth.

A study conducted by Mohamed Fawzi et al. revealed that 40% of the 50 interviewed mothers were used to reheat formula leftovers by adding hot water, which resulted in a bad bacterial profile.

Avoid using a microwave as it can create uneven heating, potentially causing hot spots that could harm your baby’s mouth and throat.

To safely warm a bottle, there are a few options:

1. Run hot water over the bottle, ensuring no water gets inside or on the nipple.

2. Place the bottle in a bowl of hot water until it reaches the desired temperature.

3. Use a store-bought bottle warmer.

When warming the formula, it’s important to shake the liquid to distribute the heat evenly. Before feeding, check the temperature by testing it on the top of your wrist. The milk should be at a comfortably lukewarm temperature, not too hot.

When you’re traveling and have to feed your baby outside your home, take everything you need for powdered formula preparation with you and make up a feed when your baby wants. A very comfortable option is to pick a ready-to-go formula.

If it’s not possible:

● Prepare the feed at home.

● Cool it down by placing it under running cold tap water or in a bowl of cold water.

● Let it cool in the back of the fridge for at least 1 hour.

● Just before you leave, take it out of the fridge.

★ In a cool bag with an ice pack, you can keep it for 4 hours.

★ In a fridge - 24 hours.

★ At room temperature while on the go, use the formula within 2 hours.

In summary, it’s important to handle baby formula with care, including its preparation, storage, and reheating. These steps are vital for your baby’s health and nutrition. If you’re looking for a variety of formula options and reliable information, visit ‘’The Milky Box’’ website. They offer a wealth of resources to support you in providing the best nourishment for your little one.

1. Formula milk: common questions - NHS. Available at: https://www.nhs.uk/conditions/baby/breastfeeding-and-bottle-feeding/bottle-feeding/formula-milk-questions/

2. ‘Guide to bottle feeding how to prepare infant formula and sterilize feeding equipment to minimize the risks to your baby’ - NHS

3. How to Prepare and Store Baby Formula – Cleveland Clinic. Available at: https://health.clevelandclinic.org/feeding-your-infant-how-to-prepare-and-store-baby-formula/

4. Infant formula: 7 steps to prepare it safely - Mayo Clinic (no date). Available at:

https://www.mayoclinic.org/healthy-lifestyle/infant-and-toddler-health/in-depth/infant-formula/art-20045791?reDate=13092023

5. Bottle-Feeding | Johns Hopkins Medicine. Available at: https://www.hopkinsmedicine.org/health/conditions-and-diseases/bottlefeeding

6. Infant Formula Preparation and Storage | Nutrition | CDC. Available at: https://www.cdc.gov/nutrition/infantandtoddlernutrition/formula-feeding/infant-formula-preparation-and-storage.html

7. How to Clean, Sanitize, and Store Infant Feeding Items | CDC.

8. Infant Formula | FDA. Available at: https://www.fda.gov/food/resources-you-food/infant-formula#preparation

9. (Handling of infant milk formulas and its impact on their microbiological quality during bottle feeding) Available at: https://www.researchgate.net/publication/265162143_Handling_of_infant_milk_formulas_and

_its_impact_on_their_microbiological_quality_during_bottle_feeding

10. Happe, R. P. and Gambelli, L. (2015) ‘Infant formula’, Specialty Oils and Fats in Food and Nutrition: Properties, Processing and Applications, pp. 285–315. doi: 10.1016/B978-1-78242-376-8.00012-0.

11. Martin, C. R., Ling, P. R. and Blackburn, G. L. (2016) ‘Review of Infant Feeding: Key Features of Breast Milk and Infant Formula’, Nutrients, 8(5). doi: 10.3390/NU8050279.

12. What should I do if I think my baby is allergic or intolerant to cows’ milk? - NHS. Available at: https://www.nhs.uk/common-health-questions/childrens-health/what-should-i-do-if-i-think-my-baby-is-allergic-or-intolerant-to-cows-milk/

13. Breastfeeding. Available at: https://www.who.int/health-topics/breastfeeding#tab=tab_1

14. Verduci, E. et al. (2020) ‘Use of Soy-Based Formulas and Cow’s Milk Allergy: Lights and Shadows’, Frontiers in Pediatrics, 8, p. 591988. doi: 10.3389/FPED.2020.591988/BIBTEX.