What happens if formula gets too hot?

Formula, or infant formula, is a food designed as a breast milk substitute for babies under 12 months of age. It typically contains proteins, fats, vitamins, minerals, and other nutrients that aim to provide adequate nutrition for infants. Formula must be properly handled and stored to preserve its nutritional quality and avoid food safety issues. One key concern is the temperature of the formula, as excessive heat can cause changes that make the formula unsafe for consumption. This article examines what can happen if formula gets too hot and steps caregivers can take to avoid problems.

Does Heat Affect Infant Formula?

Yes, heat can negatively impact infant formula in several ways:

Protein Denaturation

One issue is protein denaturation. Proteins are essential nutrients in formula, but their structures are sensitive to heat. Exposing formula to high temperatures can cause proteins to unfold or change shape. This denaturation impairs their digestion and absorption. Formula with denatured proteins may cause gut issues like discomfort, gas, and diarrhea in sensitive infants.

Vitamin Loss

Heat also degrades the vitamins in formula. Vitamins A, C, B1, B2, B6, B12, folic acid, and pantothenic acid are most susceptible to destruction by heat. High temperatures can cause losses of 30-70% of vitamins. This can reduce the formula’s nutritional value significantly.

Harmful Compounds

Heating formula too high creates potentially harmful compounds. One is advanced glycation end products or AGEs. These form when heat causes sugars in formula to react with proteins and fats. Consuming high amounts of AGEs is linked to inflammatory damage and chronic diseases. Another dangerous compound is chloropropanols, formed when formula contains added oils that are heated to over 175°C. Chloropropanols are toxicants and carcinogens.

Bacterial Growth

Finally, heat accelerates bacterial growth. Formula can contain bacteria from ingredients or improper handling. Warming allows existing bacteria to rapidly multiply to dangerous levels. Some bacteria also release more heat-stable toxins as they grow in heated formula. This increases the risk of foodborne illness.

What Temperature Makes Formula Unsafe?

Experts offer the following guidance on safe formula temperatures:

  • Storage: Unopened canned liquid formula and powdered formula should be stored at 15-25°C (59-77°F). Temperatures exceeding 30°C (86°F) can damage nutrients over time.
  • Refrigeration: Opened canned liquid formula can be refrigerated at 4°C (39°F) or colder for up to 48 hours.
  • Reconstitution: For powdered formula, water used for reconstitution should be no warmer than 70°C (158°F). Exceeding 85°C (185°F) poses scalding risks.
  • Feeding: Ready-to-feed and properly reconstituted formula should be fed at body temperature, around 37°C (98.6°F).
  • Warming: Microwaving to heat refrigerated formula is not recommended. Warmers/bottles should warm formula to no higher than 50°C (122°F).
  • Storage duration: Formula should not sit warmed for over two hours.

In summary, formula should stay refrigerated or at room temperature. Brief warming to feed babies is acceptable but heating above 50°C/122°F or for prolonged periods is harmful.

Microwaving Formula

Microwave ovens heat formula unevenly, creating hot spots that can denature proteins or scald babies. The overall risk depends on wattage, heating time, and other factors. Many experts advise against microwaving:

  • The FDA states not to warm bottles in microwaves.
  • The AAP prohibits microwaving due to burn risks.
  • Health Canada banned microwaving formula in 2021.

If microwaving, only use a small volume for a few seconds at 30-50% power. Shake well and test temperature before feeding. Never microwave a cold bottle; remove refrigerated formula from bottle first. Discard any formula that feels hot.

Signs of Overheated Formula

Look for these signs that formula has been dangerously overheated:

Physical Changes

  • Liquid looks darker, thickened, or curdled
  • Powdered formula clumps or cakes
  • An oily sheen or hard film forms on surface
  • Formula separates with clumps floating
  • Formula sticks to and scorches onto bottle

Smell/Taste Differences

  • Bitter, unpleasant smell
  • Significant loss of normal sweet taste

Infant’s Response

  • Refusal to drink
  • Decreased appetite
  • Spitting up or vomiting
  • Constipation or diarrhea
  • Excessive crying or discomfort

If formula exhibits any of these changes, err on the side of caution and do not use it. Discard formula if there is any doubt about safety or your baby refuses it.

How to Avoid Overheating Formula

Here are tips to prevent overheating formula:

  • Read and follow label instructions for storage, preparation, and warming.
  • Never leave formula sitting out warm or rewarm refrigerated bottles.
  • Don’t use a microwave or stove to heat formula.
  • Invest in a bottle warmer that heats gently to 50°C/122°F or lower.
  • Always shake or stir warmed formula well and test temperature before feeding.
  • Throw out formula left sitting out for over 2 hours.
  • Discard any excess heated formula rather than saving it.
  • Store unopened formula away from heat sources like stoves.
  • Keep formula refrigerated on outings in an insulated cooler bag.

Following safe formula handling practices reduces the chances of inadvertent overheating. Be especially careful when bottle feeding away from home.

What to Do With Overheated Formula

If despite precautions formula becomes too hot:

  • Discard it – do not take any risks feeding overheated formula.
  • Make a fresh bottle following proper procedures.
  • If on-the-go, keep your baby comfortable and hydrate with breastmilk or clean water until new formula can be prepared.
  • Watch for signs of stomach upset like fussiness or loose stools.
  • Call your pediatrician if your baby seems unwell after consuming overheated formula.

Throwing out formula may feel wasteful, but your baby’s health and safety should be the top priority. When in doubt, do not take chances with feeding formula that may have been compromised by heat.

Can Overheated Formula Make a Baby Sick?

Yes, babies can become ill if fed formula exposed to excessive temperatures:

Food Poisoning

Bacteria like Salmonella, E. coli, and Cronobacter flourish in warmer formula. If overheated formula contains high levels of these germs, babies can develop food poisoning. Symptoms are fever, vomiting, diarrhea, and severe abdominal cramps.


Infants refuse to drink formula with a scorched taste. Decreased formula intake can lead to dehydration. Signs in babies are excessive sleepiness, dry mouth, fewer wet diapers, and sunken eyes or fontanelle.

Failure to Thrive

Overheated formula can cause nutritional deficiencies if babies’ sole food source lacks intact proteins, vitamins, and minerals. Poor growth and weight gain may result.

Gastrointestinal Issues

Denatured proteins irritate the gut lining. Babies can experience discomfort, gas, constipation or diarrhea. Sensitive infants may develop oral ulcers or malabsorption.

Kidney Problems

AGEs in heated formula can accumulate in kidney tissue. This may increase babies’ risk of kidney injury and renal disease later in life.

If your baby seems unwell after drinking overheated formula, call your pediatrician right away or go to urgent care. Prompt medical treatment is needed for any suspected formula-related illness.

Long-Term Consequences of Overheated Formula

Regularly feeding infants formula heated to extremes can have lasting health consequences:

Poor Growth

Frequent loss of nutrients from degraded formulas impairs growth. Studies link higher formula temperature to reduced weight and head circumference even after controlling for diet and feeding behaviors.

Nutrient Deficiencies

Vitamin losses over time, especially vitamins C, B1, A, and folate, can cause babies to develop deficiencies. These impact vision, blood cells, immune function, and brain development.

Cognitive Issues

AGEs from heated formula are linked to inflammation in the brain. Animal studies also show AGEs inhibit production of lipids vital for brain growth. The resulting effects on neural development may manifest as cognitive or motor delays.

Kidney Disease

Accumulation of AGEs in the kidneys is associated with fibrosis and decline in kidney function. Regular intake in infancy may raise lifetime risk of chronic kidney disease.


Animal studies show chloropropanols from overheated oils cause DNA damage. While less research exists in humans, these compounds are designated as possible carcinogens.

Minimizing formula heated above 50°C/122°F protects infants’ short and long-term wellbeing. Avoiding high temperatures preserves formula’s nutritional quality.

When to Throw Out Formula

Discard formula if:

  • It exceeds refrigeration duration limits
  • It smells rancid or abnormal
  • It looks curdled, lumpy, or changed consistency
  • The bottle contains any clumps or films
  • It was heated above 50°C/122°F
  • Your baby refused it or spit it up
  • You would not consume it yourself

Other tips:

  • Write the date on cans/bottles when opening and discard within guidelines
  • Discard formula within 2 hours of warming or removing from fridge
  • When in doubt, throw it out!

Fresh formula is essential for infants’ developing bodies. Tossing formula may be disappointing, but it pales in comparison to the risks of feeding compromised formula.


Infant formula can become unsafe when exposed to excessive heat during storage, preparation, or feeding. High temperatures denature proteins, destroy vitamins, generate toxic compounds, and breed dangerous bacteria. Physical changes, smell/taste differences, and babies’ negative reactions all indicate formula has been overheated. While brief warming is acceptable, microwaving, prolonged heating, and rewarming bottles should be avoided. Overheated formula can make babies acutely ill and repeated intake may have lifelong health impacts. Caregivers should know the signs of unsafe formula and discard any they believe has been compromised by heat – when in doubt, throw it out. Following proper handling, preparation, and storage guidelines protects formula’s nutritional quality and keeps babies healthy.

Leave a Comment