Newborns eat only one thing: breast milk, formula, or a combination of both. No water, no juice, no solid food. For the first six months of life, breast milk or infant formula provides every calorie, nutrient, and drop of hydration a baby needs.
Breast Milk in the First Days
The first milk your breasts produce isn’t the white, flowing liquid most people picture. It’s colostrum, a thick, yellowish substance that comes in tiny amounts during pregnancy and the first days after birth. Colostrum is packed with antibodies that protect a newborn from infections and help their digestive system develop. The small volume is intentional. A newborn’s stomach is roughly the size of a marble on day one, so even a few teaspoons per feeding is enough.
Around two to five days after delivery, colostrum transitions into what’s called transitional milk, which increases in volume and begins to look more like the milk you’d expect. By about 10 to 15 days after birth, your body produces mature milk, which will be your baby’s complete nutrition source for months.
How Often and How Much
Newborns eat frequently. During the first few days, expect your baby to want to feed every one to three hours, which works out to 8 to 12 feedings in a 24-hour period. That pace isn’t a sign of low supply. It’s normal, and the frequent nursing helps establish milk production. As the weeks go on, most exclusively breastfed babies settle into a pattern of eating every two to four hours.
For formula-fed babies, volumes start small and increase quickly. On day one, a baby may take only half an ounce per feeding. By the end of the first week, that rises to one to two ounces. By one month, most babies drink three to four ounces per feeding. The exact amount varies from baby to baby, which is why hunger and fullness cues matter more than hitting a precise number.
Reading Your Baby’s Hunger Cues
Crying is actually a late sign of hunger. Before that, babies give subtler signals: putting their hands to their mouth, turning their head toward your breast or the bottle (called rooting), puckering or smacking their lips, or clenching their fists. Feeding at these early cues is easier on both of you, since a crying baby often needs to calm down before they can latch or take a bottle well.
Fullness looks different. A satisfied baby will close their mouth, turn their head away from the breast or bottle, and visibly relax their hands. Trusting these signals and not pushing a baby to finish a bottle helps them develop healthy eating patterns from the start.
Infant Formula Options
If you’re formula feeding, the majority of babies do well on standard cow’s milk-based formula. Despite the name, it’s nothing like pouring cow’s milk into a bottle. The milk is heavily processed: the protein is broken down to be more digestible, vegetable oils replace the butterfat, and lactose is added to match the sugar concentration in breast milk.
Soy-based formulas swap out the dairy protein for soy protein and use glucose or sucrose instead of lactose. They’re sometimes suggested for babies who can’t digest lactose, though true lactose intolerance in infants is very rare. The American Academy of Pediatrics notes there are few situations where soy formula is the better choice over cow’s milk-based options.
For babies with a confirmed cow’s milk protein allergy, which can show up as persistent vomiting, bloody stools, or failure to gain weight, the solution isn’t always soy. Up to half of infants allergic to cow’s milk protein are also sensitive to soy. These babies typically need a hypoallergenic formula where the proteins have been broken into much smaller pieces that are easier to digest. These specialized formulas cost more, so they’re generally recommended only when there’s a clear medical need.
Vitamin D Supplementation
Breast milk covers almost everything, but it falls short on vitamin D. Babies under 12 months need 400 IU of vitamin D daily, and breastfed babies (or those getting a mix of breast milk and formula) should receive a liquid vitamin D supplement starting shortly after birth. Formula-fed babies who consistently drink 32 ounces or more of formula per day get enough vitamin D from the formula itself and don’t need the extra supplement.
How to Tell Your Baby Is Getting Enough
You can’t measure how many ounces a breastfed baby takes in, so diaper output becomes the main indicator. In the first few days, wet and dirty diapers increase gradually. After day five, you should see at least six wet diapers per day, with the number of dirty diapers varying. Steady weight gain at pediatric checkups is the other reliable sign. Most newborns lose a small amount of weight in the first few days and regain it by about two weeks.
What Newborns Should Never Have
A few items that seem harmless are genuinely dangerous for babies:
- Water. Newborns should not drink plain water. Their kidneys aren’t mature enough to handle it, and even small amounts can dilute their blood sodium to dangerous levels. Breast milk and formula provide all the hydration they need, even in hot weather.
- Honey. No honey before 12 months, in any form. Honey can contain spores that cause infant botulism, a severe type of food poisoning. This includes honey mixed into water, formula, or spread on a pacifier.
- Cow’s milk. Regular cow’s milk is off-limits until a baby turns one. It can cause intestinal bleeding, contains too much protein and too many minerals for immature kidneys, and lacks the right balance of nutrients a baby needs to grow.
When Solid Foods Enter the Picture
The WHO and UNICEF recommend exclusive breastfeeding (or formula feeding) for the first six months, meaning no other foods or liquids, not even water. Around six months, babies start showing signs of readiness for solid foods: sitting up with support, showing interest in what you’re eating, and losing the tongue-thrust reflex that pushes food out of their mouth. At that point, solid foods are introduced alongside breast milk or formula, not as a replacement. Breast milk or formula remains a major calorie source well into the first year and, for breastfed babies, can continue up to two years or beyond.