Why Is My Newborn Not Gaining Weight?

Key Takeaways

Newborns typically lose about 7% of birth weight (usually no more than 8 to 10%) in the first days and regain it by around 2 weeks, with a doctor's weight check due within 48 hours of leaving the hospital.
Low calorie intake is a key cause; breastfed babies need 8 to 12 feeds per 24 hours, while formula-fed newborns take about 1 to 2 ounces per feed in the first week, rising to 3 to 4 ounces by the end of the first month.
Latching problems, excessive sleep (wake to feed after about 4 hours), and still-developing feeding skills can limit intake, so seek help from a doctor or lactation consultant; 6 or more wet diapers daily by 5 to 7 days is a good sign.
Some newborns burn more calories, such as those with breathing difficulties, which need prompt medical attention, or premature babies, who require more calories than full-term infants.

Last reviewed: November 6, 2026. Checked against current guidance from the American Academy of Pediatrics and Children’s Hospital of Philadelphia.

Being a new mom can be nerve-wracking. You keep checking the health of your baby, read endless books, and do your best to ensure they are healthy and happy. You can watch the newborn lose some of its birth weight during this time.

Before you panic, let us tell you that this is normal. During the first few days, a newborn will lose on average about 7% of its birth weight, and usually no more than about 8 to 10%. Most of the babies gain the weight back by about 2 weeks old, and then it begins increasing. Your baby should have a checkup within 48 hours of leaving the hospital so the doctor can check their weight.

However, if your newborn is not gaining weight, here are some of the reasons behind this.

1. Intake Of Calories Is Low

It is important to understand the calorie needs of your baby. For example, a breastfed baby will need feeding at least 8 to 12 times every 24 hours, or about every two to three hours. If you are feeding formula, newborns usually take about 1 to 2 ounces per feed in the first week, every 2 to 3 hours. This slowly increases to about 3 to 4 ounces per feed by the end of the first month.

Even if you are doing this, some newborns might still not be getting enough calories to gain weight.

The reasons for this include the following:

Issues with latching: Make sure that your baby is latching on correctly so that they are getting all the nutrients they need. If the issue persists, you can opt for a lactation consultant
Sleeping a lot: Many newborns sleep a lot, which means they will not be getting calories. In the first few weeks, gently wake your baby to feed if they sleep longer than about 4 hours, unless your doctor tells you otherwise
Still learning: Babies are still learning how to breathe, swallow, and suck. Many babies get better at feeding within a few days, but don’t just wait it out. Ask your doctor or a lactation consultant for help, and keep your baby’s weight checks

These are the top three reasons that the calorie intake of your newborn baby might be low. Be sure to keep a check and see if it is because of any of these issues. If that is the case, then work towards rectifying the issue. A good sign your baby is getting enough is 6 or more wet diapers a day with pale yellow urine by 5 to 7 days old, and regular yellow stools.

2. Burning Calories

All newborns have different calorie needs in the beginning. That is because some of the babies will quickly metabolize all the calories that they intake. There are many reasons why some newborns might burn more calories than others, which include:

Difficulty with breathing: If your newborn is facing difficulty breathing, they are probably exerting more effort, which means burning more calories. Fast or hard breathing needs a doctor’s check right away
Premature newborn: A premature newborn will need more calories than a full-term newborn. Breast milk is still best, but some preemies need extra calories added to breast milk or a special formula. Follow your baby’s doctor’s feeding plan
Heart issues: If your newborn has any heart problems, it will probably expend more energy and struggle to gain weight. Be sure to consult a professional to rule this possibility out

These are the top three reasons your newborn might be burning more calories, which means they don’t have enough in their system for weight gain. Your baby’s doctor can find and treat these problems so that they can have enough calories to gain a healthy weight.

3. Lower Calorie Absorption

Finally, another reason why your newborn might not be gaining weight is that they are not absorbing enough calories from the food they take in. There could be many reasons for a low-calorie absorption rate.

These include:

Sensitive or allergic to certain foods: Babies can be intolerant, sensitive, or allergic to certain foods, such as the cow’s milk protein in formula or in a breastfeeding mother’s diet. If you think your newborn has an allergy, you must seek care as soon as possible
GERD: All babies spit up, and spit-up on its own is normal. When reflux comes with poor weight gain, refusing feeds, arching or crying during feeds, or green or bloody spit-up, it may be GERD. Talk to your pediatrician about this problem
Other medical conditions: Less often, problems with the gut, such as cystic fibrosis, can make it hard to absorb nutrients. Your doctor can check for these. (Celiac disease is not a cause in newborns, since it is triggered by gluten in solid foods later on.)

These are the top three reasons that your newborn baby might not be absorbing as many calories as possible for them to thrive.

If you suspect any of these issues, we recommend that you seek medical care. It will enable you to give immediate care to your newborn baby.

Keep in mind that feeding problems and jaundice are linked. Babies who aren’t feeding well can become more jaundiced, and very jaundiced babies can be sleepy and feed poorly. If your baby’s skin or eyes look yellow, call your doctor.

So, visit the medical practitioner to rule this possibility out and help your baby gain weight without any issues.

Final Words

That was your complete guide to why your newborn baby might not be gaining weight. Don’t wait a month if you are concerned. Call your newborn baby’s healthcare practitioner if your baby is not back to birth weight by about 2 weeks, has fewer wet diapers than expected, is very sleepy or hard to wake for feeds, or you are worried for any reason. Call right away or get emergency care if your baby has a rectal temperature of 100.4°F (38°C) or higher, has no wet diaper in 6 to 8 hours, or seems limp or very unwell.

It will help you rule out any serious issues, and you can follow the doctor’s order to ensure healthy weight gain for the newborn.