Most parents count down the days until their baby’s first birthday with excitement — and not just because it’s such a huge milestone. There’s another reason why a first birthday is cause for celebration: It’s usually the point at which you can start introducing your little one to cow’s milk.

Even if you’ve loved breastfeeding and plan to continue for a while, being able to substitute some of that liquid gold for whole milk is going to free up precious minutes in your schedule. Meanwhile, cans of formula are as expensive as actual liquid gold, so no parent is going to miss forking over that cash.

So by the time your baby turns 1-year-old, you’re likely to be more than ready to make the switch. But can you do it earlier? Does it have to be cow’s milk? And what can you expect to happen once you start the transition? Here’s a guide to when — and how — to introduce whole milk.

According to the Children’s Hospital of Philadelphia (CHOP), babies over 1 year of age can begin drinking cow’s milk instead of breast milk or formula.

It should be whole milk — not a lower percentage or skim — because the fat included is good for your baby’s brain, which goes through some pretty important development in the first 2 years of life.

That said, in instances of a family history or risk of obesity or heart disease, caregivers should discuss the most appropriate choice of milk with their pediatrician.

We get that it’s tempting to start introducing milk a little sooner than 12 months, but you shouldn’t jump ahead here. Breast milk and formula contain iron, vitamin C, and other nutrients, many of which aren’t included in cow’s milk — or at least not in high enough quantities for your baby to thrive.

However, by the time your baby is 1-year-old, they’re able to compensate for many of those lost nutrients with a well-rounded diet comprising fruits, vegetables, lean protein, dairy, and whole grains.

The role of solids

Babies younger than 1-year-old aren’t eating a ton of solids and are still reliant on breast milk and formula for their nutrient needs.

Babies who begin drinking cow’s milk (as a replacement) before 12 months old may be more likely to develop anemia, gastrointestinal distress, or certain deficiencies.

There’s also too much protein in cow’s milk for a young baby’s kidneys and digestive system to process, so switching over too soon can cause issues with those body systems as well.

Finally, giving cow’s milk to infants can cause occult (unseen) bleeding in the intestinal tract.

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If your family doesn’t have a history of food allergies, you’ve probably been giving your baby some dairy since they were about 6 months old in the form of yogurt and cheese. So you shouldn’t notice allergy symptoms, although it’s possible.

Occasionally, lactose sensitivity will develop soon after the first birthday (though this is uncommon), so it’s always a good idea to keep an eye on your baby for the first week or so after making the switch. Look for:

  • irritability
  • excess gas
  • diarrhea
  • vomiting
  • skin rashes

The biggest change you’ll probably notice involves your little one’s poop. At first, your baby may have looser or harder stools (or a harder time passing stools). There may also be a temporary change in color or texture as your baby adjusts.

If you’re concerned about your baby’s poop or bowel movements, including a change in frequency or what appears to be blood in the stool, call your child’s pediatrician.

After months of sweet breast milk direct from the tap (or even just the familiarity of a particular brand of formula), your baby might not be super thrilled about the flavor, temperature, or consistency of cow’s milk. Here are some tips for a smoother transition:

  • Mix it up. Offering your baby half cow’s milk and half formula or breast milk is a great way to get them used to the taste gradually. After a few days, lower the ratio of formula or breast milk and increase the amount of cow’s milk; keep doing this until your baby is fully transitioned.
  • Warm it up. Your breast milk was at body temperature, and you probably heated formula, so handing your baby ice cold cow’s milk might be a shock. Preparing cow’s milk in the same way you prepared their formula can make the change easier.
  • Offer a sippy cup. While some babies will want to drink cow’s milk out of their favorite bottle initially, others might be totally confused that it looks — but doesn’t taste — the same as before. This can be a good time to introduce a sippy cup. Besides, 1 year of age is the time to transition away from the bottle anyway.

If you already know your baby won’t be able to tolerate cow’s milk and need a nondairy alternative, the timing is exactly the same: Wait until your baby is at least 12 months old before switching over to something like almond milk, rice milk, goat milk, or oat milk.

There are a few things to keep in mind if this is your plan:

  • Nondairy milks don’t typically contain as much protein, vitamin D, or calcium as cow’s milk, all of which your baby needs plenty of as they continue to grow.
  • Babies with nut allergies should never drink cashew or almond milk.
  • Many nondairy milks are flavored to be more palatable, but this means they may be higher in sugar than cow’s milk (so always read the labels).

According to the American Academy of Pediatrics (AAP), any nondairy milk you choose should be fortified with calcium and vitamin D. Children between the ages of 1 and 3 need 700 mg of calcium and 600 IUs of vitamin D per day.

Once your baby turns 1-year-old, you can basically keep breastfeeding on a supplemental basis for as long as you like — but what about formula? Can you keep giving it to your baby after their first birthday?

Generally speaking, you should transition your baby off formula around 12 months of age. But there are exceptions: If your baby has special dietary needs, a milk allergy, or developmental delays, your pediatrician may ask that you continue giving them some formula.

Otherwise, you should make the effort to wean them off — even if they don’t like drinking milk. But while toddlers need the nutrients found in milk, they can get them from other sources. A child who prefers not to drink milk shouldn’t be forced into it or kept on infant formula. Talk to your child’s doctor about ensuring they get those nutrients from foods in their diet.

Beyond making the switch to cow’s milk after 12 months, you’ll also need to shift the way you think about your little one’s nutritional needs. Until now, their diet was completely or mostly focused on liquid sources of nutrition like breast milk or formula. Even though you started solids around 6 months, your baby didn’t need avocados and bananas to thrive.

Now, liquid nutrition is secondary to what your baby is consuming as part of their solid food diet. Per the AAP, your baby should have no more than about 16–24 ounces of whole milk per day. This is different from the roughly 32 ounces of breast milk or formula they were consuming before their first birthday.

At this point, 2 or 3 glasses of milk every day should be offered with meals or snacks to complement your baby’s nutrition, but milk should ultimately take a back seat to healthy whole foods.

If you’re anxious to hit the formula-to-cow’s-milk milestone, we get it — but resist the urge to rush the process. Your baby needs the nutrients in formula or breast milk until their first birthday. Plus, their tummies may not be ready for cow’s milk before then.

After that, make the switch to cow’s milk or a fortified nondairy milk and continue breastfeeding if you choose. You should also beef up (pun intended) their solid food diet to make sure they’re getting the vitamins and minerals they need.