Landing on this article means one of two things: you miscalculated your baby’s formula and are terrified of the consequences (assuming you’ve already given him the formula), or are debating whether you you have to dump it, remix, and rewarm it (if you’re still holding the bottle in question). 

First things first–it happens. Newborn parents aren’t known for being well-rested and sharp-minded, after all.

There are essentially two ways to botch your baby’s formula mixture: 

  1. Mixing the formula with too much water, resulting in formula that is diluted.
  2. Mixing the formula with too little water, resulting in formula that is over-concentrated.

Regardless of which way the formula is mixed, there can be some negative consequences for your baby. As such, if you haven’t already given your baby the compromised formula, it’s best to just toss it and make another bottle. 

If you’ve mixed the formula wrong once or several times, don’t panic, and don’t beat yourself up. It happens, which is why we’re dedicating an entire article about the subject. Maybe you misread the directions, maybe you spaced out, your other children interrupted you, etc. Don’t feel guilty, you’re still a great parent, and you’re normal. 

Infant Formula Regulation

Infant formula is one of the most regulated food items in the U.S., and with good reason:  nutrition is crucial during a young infant’s life, and they need precise amounts of macro and micronutrients in order to grow and develop normally,” advises Jacqueline Winkelmann, board-certified pediatrician and child advocate. “The FDA sets minimum and maximum amounts of many of the ingredients in infant formula, and this is why it is so important that formula is mixed properly.”  

Dr. Winkelmann says the biggest danger of feeding your baby formula that has been mixed incorrectly is the electrolyte imbalance it will create, which could have potentially serious consequences. While a one-time mistake isn’t likely to cause any major problems, incorrectly mixed formula fed to your baby over the course of a few days or weeks can cause some serious issues. 

Here’s how incorrectly mixed formula can cause problems for your baby. 

Over-Concentrated Formula (Mixing Too Much Formula/Too Little Water)

You spaced out and just kept scooping. Again, it happens. If it happens once, you probably won’t notice much of a change with your baby’s routine. If you’ve done it repeatedly, you might notice some gastrointestinal issues like constipation. 

Repeatedly over-mixing formula for a consistent amount of time can have potentially serious side effects such as:

  • Weight gain
  • Dehydration. Signs of dehydration can be excessive sleepiness, no wet diapers in an eight hour period, dark urine, dry mouth, lack of tears (after the first few weeks of life), and/or a sunken spot on the head. If your baby demonstrates any of these signs, he needs to be evaluated by his healthcare provider. 
  • Electrolyte imbalance (mostly sodium and potassium)
  • Kidney issues due to excess protein

“Mistakes happen! You are not a bad parent!” says Dr. Winkelmann, “Keep a close eye and look for any changes in behavior or hydration status. If you know your baby has been fed over-concentrated formula several times, it’s best to discuss with her healthcare provider.”

Diluted Formula (Mixing Too Little Formula/Too Much Water)

Did you put in one scoop or two? By the time the thought occurs to you that you potentially diluted your baby’s formula, he’s already downed the bottle. Don’t panic. One diluted bottle isn’t going to cause a major problem for your baby, but over time, diluted formula can cause serious issues for your baby’s health.

It’s also important to mention that some parents will intentionally dilute their baby’s formula to attempt to stretch it and make it last longer. This is dangerous and not necessary. Through the government’s WIC program and many other local and state programs, there should be no reason why you cannot get access to enough formula for your baby. 

Possible risks of diluted formula include:

  • Water intoxication. Dr. Winkelmann advises that this is a rare occurrence, but that young infants are especially vulnerable because they’re so small. Water intoxication is defined as the over-consumption of water leading to a dilution of electrolytes, mainly sodium, potassium, and calcium. Symptoms of water intoxication include large amounts of very clear urine, restlessness, fussiness, sleepiness, lethargy, dizziness, vomiting, and even seizures in severe cases.
  • Weight loss or delayed weight gain. Diluted formula can result in babies that do not thrive and gain the appropriate amount of weight they should. It’s important to visit your baby’s health care provider for well checks so your baby’s growth curve can be followed. If your baby is not gaining weight adequately, this may be a sign you aren’t mixing the formula correctly. 
  • Developmental delays. “If you’ve fed your baby diluted formula a couple of times by mistake, there’s probably no harm,” says Dr. Winkelmann, “but over time, diluted formula will cause your baby to slow on their growth and even lose developmental milestones. Diluted formula over a period of time has serious consequences, including developmental delays, seizures, and even death.” 

Make sure you’re diligent in mixing formula correctly in the future. “If your baby gets hungry earlier than normal, you can offer an additional bottle of correctly mixed formula sooner than you would normally,” advises Dr. Winkelmann.

Formula Feeding Best Practices

If you’re feeling a little lost, or just want a refresher, Dr. Winkelmann has some helpful tips to ensure you are correctly and safely mixing formula and feeding your baby properly:

  • Clean hands first. Always wash your hands with soap and water, or use hand sanitizer, before making your baby’s bottles.
  • Read the directions. Then read them again! If the instructions on the canister are in another language, make sure you translate it correctly before you begin mixing. In the United States, most infant formula will be mixed at a ratio of one scoop per two ounces of water. 
  • Use the scoop that’s there. Always use the original scoop that comes in the formula container you’re currently using. Some formulas have different sized scoops, so it’s important to make sure you use the correct one.
  • Fill the scoop. When measuring formula powder, fill the scoop that comes with the formula you are using. Use a knife to scrape off excess powder. You don’t need to pack the scoop with powder. 
  • Mix well. Add the formula powder to the water and mix well.
  • What type of water should you use? If you’re wondering if it’s safe to use tap water, Dr. Winklemann says, “Most city tap water will be okay to use to mix your baby’s formula. It is best to run cold tap water for one minute and then fill the bottle. It is best not to use warm tap water in order to avoid potential lead exposure. If you’re concerned, you can always boil the water for one minute and then let it cool.”

There are exceptions to using tap water. If you have untested well water, city water with known recent contamination (i.e. you are currently under a boil notice), or if your baby has an immune deficiency, you can use distilled water, bottled water, or filtered tap water, but it is best to avoid regular tap water in these instances. 

  • Temperature. Always ensure the proper bottle temperature when feeding your baby. Most babies prefer formula that is body temperature (slightly warm to the touch). It’s okay for your baby to take formula at room temperature or even cold if they don’t mind it, however most babies prefer warmer formula. If you are mixing formula for the entire day, it’s best to warm it up (by submerging the bottle of formula in hot water or using a bottle warmer) to at least room temperature. Never use a microwave to heat formula.
  • Prepared formula. Once you’ve prepared formula and fed it to your baby, any unused portion still in the bottle must be thrown away one hour after feeding. Unused, prepared formula can be stored in the refrigerator for 24 hours. Ready to feed formula and concentrated liquid can be stored and/or covered for no longer than 24 hours. 

Formula does not require refrigeration before it has been prepared. Bottles can be made for each feeding and fed room temperature or warmer. 

  • How to travel with formula. If you need to take your baby’s formula on the go, which you will likely need to do quite a bit, use a container and scoop the correct amount of formula for your baby’s bottle (ex. If your baby takes six ounces, fill the container with three scoops of formula). Bring water bottles and mix your baby’s bottle when needed.
  • Other best feeding practices. Dr. Winkelmann advises you should always hold your baby while feeding him, never prop the bottle up to feed him. While feeding, pause to burp your baby every ten minutes or so.

Mixing the formula incorrectly happens, and it usually won’t result in any major harm to your baby. However, over-mixing or under-mixing formula for extended lengths of time can cause major health issues for your baby, so be mindful as much as you can, and don’t stress too much if you have a formula mixing mishap once in a while. 







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