Accidentally Gave Baby The Wrong Formula – What’s The Worse That Can Happen?

Giving the wrong formula to a baby in a short course is nothing problematic. Formula milk contains the same core components with a slight difference in the added ingredients that vary in every brand. Your baby should be okay if the switch does not pose any digestive problems. If the formula is age-appropriate and does not contain allergens for your baby, you can continue giving it. However, if the formula is not specific to your baby’s age, you should switch them back to their original milk.

You can either make your baby’s formula over-diluted or over-concentrated. If you have done it only once or twice, there’s no need to panic so much.

But giving wrongly mixed formula or wrong stage formula to your baby can develop serious health issues if done over an extended period.

What happens if the baby drinks the wrong formula?

The worst your baby can get from the wrong formula is digestive issues like constipation or diarrhea. However, these reactions are rare and happen once in a while.

But if your baby has intolerance and allergy, the wrong base ingredient can cause allergic reactions.

While most commercial infant formulas are the same, there are specialty baby formulas for specific dietary needs.

Generally, infant milk is made from cow’s milk protein or whey protein. So, those babies who can’t digest protein are given hypoallergenic or extensively hydrolyzed formula milk.

Specialty formulas are also famous for babies with severe acid reflux, premature babies, and those with metabolic disorders and heart problems.

If giving the wrong formula triggers an allergic reaction in your baby, take them to the pediatrician immediately.

Newborn formula vs. infant formula vs. toddler milk

In breastfed babies, the mother’s breastmilk composition changes as the baby age. It may also change if either is sick, making it almost miraculous and biologically custom milk for babies.

Formula milk is designed to mimic the components of breast milk. That is why they also change according to the baby’s age. They are available as Newborn Formula, Stage One, and Stage Two formula milk. So, the nutrient concentration in this formula varies at each stage.

The newborn formula contains a high concentration of Vitamin D and iron, and Vitamin D is an essential nutrient that all babies need right after birth.

This is where breastmilk and newborn milk may differ since breastmilk does not contain enough Vitamin D that formula milk has.

Breastfed babies still need an infant Vitamin D supplement to prevent a deficiency.

Infant formula contains a complete nutritional requirement for the baby and is regulated by the Food and Drug Administration (FDA).

The federal agency oversees the nutrition profile, ingredients, production, and labeling of infant formula brands. Infant formula is the sole source of nutrition in babies.

Thus, they should meet the recommended nutritional needs.

Toddler milk, on the other hand, contains a higher amount of calcium and phosphorus, similar to whole milk.

FDA isn’t stringent in its components, and their nutrients may be high or low in every milk brand. It’s only used as a supplement to solid foods and is unnecessary if the child eats a balanced diet.

What happens when you give wrong-stage milk to your baby?

Mixing the wrong kind of formula into a baby's bottle.

Having both a toddler and an infant in the house has a high possibility of formula mix-ups once in a while.

It can make a parent worry about whatever symptoms would arise, pondering whether to call the doctor or not.

If you give your infant your toddler’s bottle, they can still digest the milk without any adverse effects. It will not cause any health problems if given once or twice by mistake.

However, it would be best if you did not make toddler milk a replacement for infant formula. The high protein and mineral concentrations are too much for the baby’s developing digestive system.

Whole cow’s milk can cause intestinal bleeding and may risk anemia in infants. But again, it is only possible if cow’s milk is given for a more extended period.

What happens if you put an extra scoop of formula in a feed?

Let’s consider a common situation amongst parents where you’re half-awake preparing your baby’s milk to pacify them in the middle of the night.

But you’re jolted awake upon realizing that you may have added a couple of extra scoops to the bottle.

Before worrying, it’s important to realize that concentrated formula will not cause any harm if it happens only once. However, it may become an issue if done regularly for a long period.

It can cause hyperosmolality, which may cause the blood to become concentrated, risking heart and kidney failures.  

What happens when you prepare a diluted formula?

It may not sound like a big deal when the powdered formula is falling short of only a small quantity, and you think of compensating for it with an extra bit of water.

But the diluted or watered-down formula, when given over time, can slow down a baby’s growth and cause developmental delays.

Water intoxication can occur when an abnormal electrolyte level is due to diluted formula. It causes the baby to vomit, become fussy, lethargic, or even experience a seizure.

Do not make it a habit of watering down a feed to extend a packet of formula.

If you are being economical, breastfeed or express breastmilk for your baby, and it is inexpensive and chock-full of nutrients tailored to their specific needs.

What are the symptoms of a baby’s intolerance to the wrong formula?

A mother is handling her fussy baby suffering from milk allergy symptoms.

The wrong formula is problematic if your baby has dairy intolerance or milk allergy.

Call your child’s pediatrician if you are concerned about symptoms arising from your baby drinking the wrong formula. Milk allergy symptoms that need immediate attention are:

  • Vomiting
  • Loose or watery stool
  • Skin reactions like rashes and swelling
  • Difficulty breathing
  • No urine in over 8 hours
  • Blood in poop

Loose stool or constipation is generally prevalent in infants and will disappear in a few days. Consult the pediatrician if your baby has watery stool every 2 hours to address the dehydration.


Can I switch milk if my baby doesn’t like his formula?

Switching formula milk is safe if your baby does not have allergies or food intolerances.

Even babies with feeding and bowel issues can eventually switch to regular formula milk if their conditions have improved.

Is it okay to give my baby two different formulas?

Yes, as long as they are of the same type, such as cow’s milk-based, soy, extensively hydrolyzed, or amino-acid based. You can even mix two different formulas if you think your baby responds better to them.


Unintentionally giving the wrong formula to babies does happen, but it is not worth fussing about.

When given once in a while, a wrong stage or wrongly-mixed formula does not cause any harm, but what is harmful is the bad and unsanitary preparation of formula milk.

Prepare the baby’s milk with good sanitation and proper food safety practices. Follow the package direction or the pediatrician’s instructions to keep your baby healthy and safe. 

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Ann Marie is a licensed nurse in the Philippines. She experienced handling and assisting deliveries of newborns into the world. She also trained in labor rooms and pediatric wards while in nursing school - helping soon-to-be mothers and little kids in the process. Though not a mother by nature but a mother by heart, Ann Marie loves to take care of her younger cousins as well as nephews and nieces during her free time.

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