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How Long Does It Take For Baby To Adjust To Formula Change?

When you choose to bottle feed your baby, you need to consider what type of formula you’ll be feeding them. Not all formula is the same. One may make your baby spit up, another may cause gas, and a third might just be perfect.

The thing is, it’s not good to constantly change your baby’s formula as this can have an impact on them. Babies have underdeveloped digestive systems that are extremely sensitive. So it can damage their stomach.

In addition, you want to make sure that your baby has time to adjust to the new formula. If your little one previously had gas, and they continue to have gas on their new formula, it could be that they haven’t adjusted yet.

How Long Do Babies Need to Adjust to New Formula?

Some babies will adjust to a new formula in a week. Other babies might take longer up to six weeks. Instead of giving your baby a timeline, it’s better to pay attention to symptoms and discomfort. One of the easiest ways to do this is to document it.

For example, if your baby was constipated, keep track of how often they have a bowel movement. Note any new symptoms, such as gas or signs of discomfort. As you keep track of those symptoms, you can review previous symptoms so that you can see if your baby is starting to improve or not.

If they are not, they might not have adjusted yet, or they might need a different formula. If your baby hasn’t improved in three weeks, give your pediatrician another call.

baby crying

Signs Your Baby Is Having A Hard Time With The New Formula

Sometimes, you’ll realize that you just switched formulas and your baby is having a hard time with the new one. This isn’t always easy to spot, though. Watch for these signs that your baby might need to switch formulas again.

Allergic Reaction

If your baby has any signs of an allergic reaction to a new formula, it’s important to switch his formula and contact your pediatrician immediately. This is something to watch out for if your baby was previously on soy formula and you’ve switched them to one that is milk-based.

Milk allergies are common in infants. Allergic reactions can be mild or severe. Symptoms include:

  • Rashes
  • Hives
  • Vomiting
  • Excessive diarrhea (some diarrhea in infants is normal. Contact your pediatrician to determine if your baby falls within the normal range.)
  • Respiratory problems

Signs Your Baby Is Having A Hard Time Adjusting

Every formula is not created the same. If you recently switched formulas and have noticed a sudden onset of these symptoms, it’s a sign that your baby might have an upset stomach from their new formula.

  • No longer sleeps through the night
  • Cries more frequently
  • Tenses up
  • Excessive gas, constipation
  • Vomiting
  • Grimaces or scrunched up face as though they are in pain

What To Do If Your Baby Is Having A Hard Time Adjusting?

Although it makes sense to switch formulas again, that’s not always the answer. If your baby is having an allergic reaction, you’ll need to switch formulas.

If they have a mild symptom, like gas, there are other things you can try. Gas relief drops and burping your baby more while feeding them can both work to alleviate gas in infants.

If you’re not sure, contact your pediatrician. They are there to help your baby when they’re is sick, but also to provide you with guidance as you strive to be the best mother you can be.

Reasons For Switching Formula

A lot of parents wonder whether they should switch formulas. Well, it depends. If your baby spits up every time they eat, and you’d like to try the Similac formula that is specifically designed for spit up, there’s nothing wrong with that.

You’re the parent, and you can switch formulas whenever you would like to.


If your baby has allergies, you definitely need to switch formulas. If they have a milk allergy, switching to soy formula is usually best.

If they have other allergies, switching to a hypoallergenic formula or all-natural formula might be safer. Safety should always come first, and allergies can cause dangerous respiratory symptoms.


You don’t always need a health reason to switch formulas. Some parents discover that a particular brand is made with more natural ingredients or does not use GMO’s, and they would prefer to give their baby that.

If you have a particular preference as you learn more about different types of formula, there is nothing wrong with switching your baby to something that you deem to be better for them.

Digestive Issues

Some babies handle certain formulas better than other ones. My grandson was on Similac Neosure for quite a while. It was horrible. He had random bouts of constipation or diarrhea. He was fussy. The poor thing would scream in pain. He had every symptom of digestive problems.

The doctor insisted he needed a preemie formula and refused to switch him. So, we found Enfamil EnfaCare. He seems to handle that a little bit better. If your baby is having digestive issues, there’s nothing wrong with switching formulas.


Let’s face it: baby formulas are expensive! If you started off on the most expensive formula and want to switch to save some cash, that’s fine too. This is one of the popular reasons that parents change formulas.

Certain brands are cheaper. One of the reasons I like Gerber is because Walmart has a brand that is the same as Gerber, and it’s only half the cost. Some brands, like Enfamil Enfacare, don’t seem to have an off-brand version available.

TIP: Buying a cheaper brand or buying in bulk online are both awesome ways to save money on formula too!

Vitamin Deficiency

If your little one has a vitamin deficiency, like low iron, they might need to switch formulas. Some formulas are fortified with iron or other vitamins to give your baby the boost that they need if infant vitamins aren’t enough for them.

Usually, your doctor or local WIC office will tell you if your baby has a vitamin deficiency and needs to switch formulas. You shouldn’t try to do this yourself.

Switching Formula Brands

Switching from one type of Enfamil to another is common, but most people worry when it comes to switching brands, like switching from Enfamil to Similac. Not all brands are made the same, but switching between brands if perfectly fine.

Remember that it might take a little bit longer for your baby to adjust to the new formula, though. Give them a week or two to determine if they can tolerate the new formula.

Transitioning To A New Formula

If you decided to give your baby a new formula, there are two ways to do it. You can switch cold-turkey to a new formula, or you can transition into a new formula. There are pros and cons to both ways.

Switching All At Once

If you switch all at once, it means that you abruptly stop giving your baby one formula and immediately switch to another. This is common for parents that are switching due to allergies, but there are a few things to know first.

How Long Does It Take For Baby To Adjust To Formula Change?

When you switch all at once, you can go through an adjustment period. Some babies will adjust within a few days, but others might take weeks to adjust. It depends on your baby, and on the formula.

Switching from soy formula to a milk-based formula will be harder on the digestive system, and it might take your baby a while to get the hang of digesting it.

While you’re going through the adjustment period, you might notice that your baby has sporadic gas or tummy troubles. This is normal.

If the problems persist, discuss other options with your pediatrician, or simply ask them how long does it take for the baby to adjust to formula change. They will have experience regarding the specific formula that your baby is on.

Necessary For Allergies

This method of switching formulas is necessary if your baby has allergies, such as a milk allergy. If you do not switch formulas as soon as possible, your baby could have a severe allergic reaction, such as respiratory problems.

If your baby has an allergy, don’t try to transition them to a new formula, simply switch them.

Necessary For Extreme Discomfort

If your baby is having severe discomfort that leaves him crying for hours, switching all at once is usually worth it. Granted, they might have a few problems with the new formula, but it can prolong their discomfort to slowly transition formulas.

baby bottle feeding

Slowly Transitioning

Slowly transitioning your little one from one formula to the next involves mixing formulas. You substitute a little bit of the old formula with the new formula. Then, each day you add a little bit more of the new formula to the bottle until your baby is only drinking the new formula.

How Long Does It Take For Baby To Adjust To Formula Change?

When you slowly transition your little one, you will have a longer adjustment period. It will take a week to completely switch to the new formula, so you won’t be able to see how well they adjust until after that.

The adjustment period is usually a bit different than switching formulas suddenly.

Fewer Side Effects

Babies that are suddenly switched from one formula to the next might have gas or indigestion from the switch, especially if you switch brands.

When you slowly transition formulas, though, your little one will have enough transition period to get used to the new formula. This means that they will have less digestive problems.

When Should You Transition Slowly?

Transitioning slowly is ideal if your baby does not have allergies or severe discomfort from the previous formula. It’s also a great idea if you are switching between brands.

If you don’t have to switch suddenly, go with transitioning slowly to give your little one time to adjust.

Baby Formula FAQs’


How Long Does It Take For Baby To Adjust To New Formula?

It varies depending on your baby. Some will adjust in a week, some will take a few weeks. If your baby is still having problems in two weeks, contact your pediatrician.

Is It Okay To Switch Formula?

Yes, it’s perfectly fine to switch formula. Most formulas that are the same type, like soy-based with natural ingredients formulas, have similar ingredients. This type of switch is not likely to cause any digestive problems, either.

Can Switching Formula Cause Problems?

It is common to see stool changes after switching formulas, but this is usually not a problem. Switching formulas is not known to cause problems.

You can also switch back and forth between different formulas without problems. If you do notice negative side effects, it might just take your baby longer to adjust.

How Long After Switching Will I See A Difference?

If you’re switching for fussiness or upset stomach, you should notice a difference within a few days. If it’s for a milk allergy, it can take weeks for a baby to feel 100% better.

Do I Have To Mix Formula When Switching To A New Formula?

No, you don’t. If switching brands, it can make the adjustment period easier on little ones. If you’re sticking with the same brand, you should be fine if you choose to switch all at once.

When wondering how long will it take for a baby to adjust to a new formula, there is no exact answer. Some formulas will reduce fussiness quickly, and other times a baby, like one with milk intolerance, may take 2-6 weeks to start feeling more comfortable.

It depends on your baby. If you are concerned, never hesitate to contact your pediatrician.