Learn how to choose infant formula by understanding stages, protein types, ingredients, specialised formulas, preparation and when to switch.
Dr. Nallapu Siri
Standing in front of a shelf of infant formula tins can be confusing. Labels may mention whey, casein, hydrolysed proteins, lactose-free, Stage 1, Stage 2, DHA or prebiotics, but it is not always clear what these terms mean or whether they matter for your baby. Understanding how infant formulas differ can help you read labels more confidently and discuss the most suitable option with your baby's paediatrician.
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Infant formulas are designed to provide the nutrients babies need when formula feeding is required. The products may look similar, but their formulations and intended uses can differ.
When comparing products, start with the information that directly affects suitability:
The exact ingredient list and nutritional composition should always be checked on the current product packaging because formulations can differ between products and may change over time.
Protein is one of the main differences between infant formulas. The type and degree of processing can determine whether a formula is intended for routine feeding or for a specific nutritional need.
Most standard infant formulas are based on cow's milk that has been modified to meet infant nutritional requirements. They generally contain whey and casein proteins along with added carbohydrates, fats, vitamins and minerals.
According to NHS guidance, first infant formula is suitable from birth and can remain the main formula through the first year when formula feeding is needed.
Partially hydrolysed formulas contain proteins that have been broken down into smaller fragments.
Some products are marketed as comfort formulas for digestive symptoms such as colic or constipation. However, evidence for these benefits is limited. NHS guidance also states that partially hydrolysed formula is not suitable for babies with cow's milk allergy.
If your baby has persistent digestive symptoms, it is better to discuss them with a healthcare professional rather than changing formula repeatedly.
Extensively hydrolysed formulas contain proteins that have been broken down more extensively than in partially hydrolysed formulas.
For babies with confirmed cow's milk allergy, an extensively hydrolysed formula is commonly used as a specialised option. The 2024 ESPGHAN position paper notes that an amino-acid-based formula may be considered in severe cases or when an extensively hydrolysed formula is not tolerated or does not provide adequate improvement.
These formulas should therefore be selected with medical guidance rather than simply because they appear to be easier to digest.
Amino-acid-based formulas contain individual amino acids rather than intact milk proteins or larger protein fragments.
They are specialised products generally reserved for particular medical situations, including some infants with severe cow's milk protein allergy. Their use should be guided by a paediatrician or paediatric allergist.
Soy-based formulas use soy protein instead of cow's milk protein. They may be considered in specific circumstances, but they are not automatically appropriate for babies with cow's milk protein allergy because some infants can also react to soy.
NHS guidance states that soya formula should only be used when recommended or prescribed by a healthcare professional and is generally considered from 6 months under medical supervision.
Formula stages are generally based on age rather than weight, but the names and age ranges can vary between products.
First infant formula is intended for babies from birth. It can remain the main formula through the first year if formula feeding is needed.
According to NHS guidance, there is no need to switch to follow-on formula simply because a baby reaches 6 months. First infant formula can continue as the main milk drink through the first year.
Follow-on formula is generally labelled for babies from 6 months onwards.
However, moving to follow-on formula at 6 months is not essential. NHS guidance states that babies can continue with first infant formula as their main drink until 12 months. Follow-on formula should not be given to babies younger than 6 months.
Growing-up or toddler milks are marketed for children over 12 months. They are not automatically necessary simply because a child has reached the toddler stage.
NHS guidance states that children over 1 year do not need formula milks, including growing-up and toddler milks, as part of a normal varied diet.
The important point is to follow the age range printed on the product rather than choosing a higher stage because it appears to contain more nutrients.
Most babies who need formula can use a standard infant formula, but some medical conditions require a different formulation.
A specialised formula may be considered for conditions such as:
A specialised formula should not be selected solely because a baby has gas, spit-up or occasional fussiness. These symptoms can have many causes and do not necessarily indicate that a different formula is needed.
Changes in stools, gas or spit-up can occur during infancy and do not necessarily mean that a formula is unsuitable.
Some symptoms, however, warrant discussion with a paediatrician.
These include:
A single symptom does not necessarily indicate an allergy or intolerance. Your paediatrician can consider the baby's overall feeding pattern, growth and symptoms before recommending a formula change.
Parents may consider changing formula because of digestive symptoms, product availability, cost or concerns about tolerance. However, changing formulas repeatedly without identifying the reason can make it harder to understand what is causing a baby's symptoms.
Before changing formula, consider the following:
For a healthy term infant, changing between standard formulas may be possible when needed. If your baby has a diagnosed allergy, metabolic condition, feeding difficulty, poor weight gain or a history of prematurity, seek medical advice before changing formula.
Once you have chosen a formula, preparing it correctly is just as important as choosing an appropriate product.
Powdered infant formula is not sterile. WHO guidance on the safe preparation of powdered infant formula recommends using water at at least 70°C when reconstituting the powder to reduce the risk from bacteria that may be present in the formula.
However, preparation instructions can vary between products and circumstances. Always follow the instructions printed on the specific formula packaging where they provide product-specific directions.
Use the exact amount of water and powder specified on the label.
As CDC guidance explains, too much water can mean the formula does not provide enough nutrition, while too little water can make a baby's kidneys and digestive system work harder.
Wash your hands before preparing a feed and clean and sanitise feeding equipment appropriately.
Bottles, teats and other equipment should be cleaned according to age-appropriate hygiene guidance and the manufacturer's instructions.
After preparation, cool the feed to a comfortable temperature if necessary and check it before feeding.
CDC guidance advises against heating formula in a microwave because uneven heating can create hot spots that may burn a baby's mouth or throat.
Freshly prepared formula is preferable because powdered formula is not sterile.
According to current CDC guidance, prepared formula should be used within 2 hours of preparation if it remains at room temperature. If it is not going to be used within 2 hours, it should be refrigerated promptly and used within 24 hours. Once feeding begins, the formula should be used within 1 hour, and any remaining formula should then be discarded.
NHS guidance similarly advises that a feed should ideally be made fresh when needed and that unused formula kept at room temperature for more than 2 hours should be discarded.
Product instructions may be more restrictive, so always check the specific formula label.
Once opened, powdered formula should be kept tightly closed in a cool, dry place rather than in the refrigerator.
CDC guidance states that most powdered infant formulas should be used within one month of opening, but the exact period can vary by product. The manufacturer's instructions should therefore be checked before use.
Never use formula after the expiry or "use by" date printed on the packaging.
Parents may notice ingredients such as DHA, ARA, prebiotics and other added nutrients on formula labels.
These ingredients can be useful to understand, but their presence should not be treated as proof that one formula is universally better than another.
DHA and ARA are long-chain polyunsaturated fatty acids found naturally in human milk and added to many infant formulas.
Their inclusion is part of the overall nutritional composition of the formula. Parents do not need to choose a product solely because its label highlights these ingredients.
Prebiotics are ingredients that can support the growth or activity of certain gut microorganisms.
Some infant formulas contain prebiotics, but their presence does not mean that the product will necessarily prevent colic, constipation or other digestive problems in every baby.
Infant formulas contain nutrients such as iron, calcium and vitamin D in amounts intended to contribute to infants' nutritional requirements.
When comparing formulas, look at the complete nutritional information rather than focusing on one highlighted ingredient.
Formula selection does not always require a medical appointment, particularly when a healthy term infant is using an age-appropriate standard formula. However, professional advice is important when there are concerns about feeding, growth or a possible medical condition.
Speak to your baby's paediatrician if:
A healthcare professional can help determine whether the symptoms require a formula change or another type of assessment.
Choosing infant formula is less about finding a universally "best" product and more about finding an age-appropriate formulation that meets your baby's individual nutritional needs. Reading the label can help you understand the formula's stage, protein source, carbohydrate source and other ingredients, while specialised formulations may be needed for particular medical conditions. First infant formula can generally remain the main formula through the first year, so changing stages or products is not automatically necessary at 6 months. When a formula change is being considered, particularly because of persistent symptoms or a medical condition, discussing the options with your baby's paediatrician can help ensure the change is appropriate.
Start by checking that the formula is suitable for your baby's age and then consider whether your baby has any specific nutritional or medical needs. Healthy term infants can generally use a standard first infant formula, while specialised formulations may be needed for conditions such as cow's milk protein allergy or certain metabolic disorders. Your paediatrician can advise you if there are concerns about tolerance, growth or feeding.
No. Follow-on formula can be used from 6 months, but it is not necessary. NHS guidance states that first infant formula can continue as the main milk drink through the first year.
No. Partially hydrolysed formula still contains cow's milk proteins and is not suitable for treating confirmed cow's milk protein allergy. An extensively hydrolysed formula is commonly used instead, with an amino-acid-based formula considered in some severe cases.
According to current CDC guidance, prepared formula should generally be used within 2 hours of preparation if kept at room temperature. Once feeding begins, it should be used within 1 hour. If prepared formula will not be used within 2 hours, it should be refrigerated promptly and used within 24 hours.
Not necessarily. Gas and spit-up are common in infancy and do not automatically mean that a formula is unsuitable. If symptoms are persistent, severe or accompanied by vomiting, blood in the stool, poor weight gain, feeding difficulties or allergic symptoms, speak to your paediatrician before changing formula.
