Baby Weight Loss: When Is It a Concern?

Learning that your newborn has lost weight can feel alarming. But in most cases, this is completely normal. This article explains which weight loss is expected, which requires attention, and how to track your baby's weight.

Normal Weight Loss in Newborns

The NHS says it is normal for babies to lose some weight in the first few days after birth. In the US, the American Academy of Pediatrics (AAP) looks for no more than 8 to 10% of birth weight lost in the first few days before weight starts to rise again.

Expected recovery time: Your baby is weighed during their first 2 weeks to check they are regaining their birth weight. The NHS says most babies are at or above their birth weight by 3 weeks, and UNICEF UK's leaflet for breastfeeding mothers says your baby should be back to birth weight by two weeks and then continue to gain.

Warning Signs That Need Attention

• A large amount of weight lost after birth (the AAP looks for no more than 8 to 10% of birth weight)
• Still not back to birth weight by 3 weeks (NHS)
• Fewer wet and dirty diapers than expected (the NHS looks for at least 6 heavy, wet nappies every 24 hours from day 5)
• Baby is constantly sleeping and can't be roused to feed
• Jaundice visibly worsening
• Baby's mouth or eyes look dry (signs of dehydration)

If you notice any of these signs, contact your doctor or midwife without delay.

Breastfeeding and Weight

The most common cause of weight loss in breastfed babies in the first weeks is breastfeeding difficulties: inadequate latch, low milk supply, or infrequent feeding. If your baby hasn't returned to birth weight by 3 weeks, the NHS says a midwife or health visitor will support you and talk to you about how feeding is going, and you can ask for help from a breastfeeding specialist at any point.

The NHS and UNICEF UK say to feed your baby as often as they want and for as long as they want, and to ask for help early if you are worried about how much milk your baby is getting.

Slow Weight Gain in Older Babies

After the newborn period, temporary weight gain slowdowns are common — especially around the solid food introduction stage (6 months) — and are usually normal. However, see your pediatrician if:

• The growth curve consistently trends downward at regular checkups
• Expected height gain isn't occurring
• The child has lost activity, appetite, or energy

Baby weight tracking and growth curve information — see our detailed guide for more.