Babies cry at night for a handful of predictable reasons, and most of them are completely normal. Hunger, short sleep cycles, developmental changes, and physical discomfort top the list. The specific cause depends heavily on your baby’s age, so understanding what’s happening at each stage can help you figure out what your baby actually needs at 2 a.m.
Short Sleep Cycles and Frequent Waking
Newborns sleep 16 to 17 hours a day, but they do it in stretches of only one to two hours at a time. That’s because infant sleep cycles are dramatically shorter than adult ones. Every time your baby completes a cycle and briefly surfaces into lighter sleep, there’s a chance they’ll wake fully and cry instead of drifting back down. Adults do this too, but we’ve learned to roll over and fall back asleep without noticing. Babies haven’t figured that out yet.
Making this harder is the fact that your baby’s internal clock isn’t fully online for months. The pineal gland, which produces the sleep-regulating hormone melatonin, doesn’t start releasing detectable amounts until around six weeks of age. Even then, levels stay low through three or four months. Melatonin only becomes a stable part of your baby’s sleep-wake cycle around six months, and by 12 months it’s still only at about half of adult levels. Until that system matures, your baby’s body has limited ability to distinguish night from day or to consolidate sleep into longer stretches.
Hunger and Growth Spurts
Hunger is the most common reason babies under six months wake and cry at night. Their stomachs are small, breast milk digests quickly, and they genuinely need to eat frequently. This is especially true during growth spurts, which typically happen around 2 to 3 weeks, 6 weeks, 3 months, and 6 months. During a growth spurt, babies may want to feed as often as every 30 minutes, and they tend to be fussier overall. These bursts of intense feeding usually resolve within a few days.
If your baby is around six months and still waking to eat, that can be normal too. Babies who are breastfed may still need a night feed at this age, and those who have started scooting, crawling, or practicing sitting up during the day are burning more calories and may need to replenish them overnight.
Sleep Regressions at Every Stage
Just when you think you’ve figured out your baby’s sleep pattern, it falls apart. These disruptions, called sleep regressions, happen at fairly predictable ages and are tied to your baby’s developing brain and body.
The first major one hits around four months. This is when your baby’s sleep architecture starts shifting toward adult-like patterns, with more defined stages of light and deep sleep. It feels like a regression, but it’s actually a leap forward, and it’s often the roughest one because everything about how your baby sleeps is reorganizing.
Around eight months, many babies start pulling themselves to standing or learning to crawl, and their brains seem unable to stop practicing these new skills, even during sleep. The 12-month regression coincides with a growing awareness of the world and often with early steps or cruising along furniture. By 18 months, separation anxiety becomes a major driver. Your toddler doesn’t want to be away from you and may resist bedtime or wake crying for you. At 24 months, the causes shift again: potty training, transitions to a toddler bed, nighttime fears, and nightmares can all play a role.
Sleep regressions typically last two to six weeks. They’re frustrating, but they signal that your baby’s development is on track.
The Overtired Trap
This one is counterintuitive: a baby who is too tired actually has a harder time falling and staying asleep. When your baby misses their sleep window and becomes overtired, their body releases a surge of cortisol and adrenaline. Cortisol regulates the sleep-wake cycle, and adrenaline triggers a fight-or-flight response. With both of those hormones elevated, your baby gets wired instead of drowsy. They’ll fight sleep, cry harder, and wake more frequently once they finally do fall asleep.
Signs of an overtired baby include pulling at ears, arching the back, clenching fists, and becoming increasingly difficult to soothe. Watching for early sleepy cues, like yawning, eye rubbing, or turning away from stimulation, and putting your baby down before they hit the overtired zone can prevent this cycle from starting.
Separation Anxiety
Between 6 and 12 months, most babies develop separation anxiety. This is directly linked to a cognitive milestone called object permanence: your baby now understands that you still exist even when you leave the room. The problem is they don’t yet understand that you’ll come back. When they wake in the dark and you’re not there, they feel genuinely unsafe and cry to bring you back.
Separation anxiety typically peaks in the second year of life and gradually fades by around age three. At night, it often shows up as your baby needing you right next to them to fall asleep, or waking and crying the moment they realize you’ve left.
Teething: Not What You Think
Teething gets blamed for almost every bout of nighttime crying, but the evidence tells a different story. A longitudinal study published in The Journal of Pediatrics used video monitoring to track infant sleep on the nights directly before and after tooth eruption and compared them to non-teething nights. The result: no significant differences in any sleep measure. Over half of parents in the study reported that teething disrupted their baby’s sleep, but the objective recordings didn’t support it.
This doesn’t mean teething is painless. Babies may be irritable during the day when a tooth is coming through. But if your baby is consistently waking and crying at night, teething is probably not the primary explanation, and it’s worth looking at other causes on this list.
Reflux and Physical Discomfort
Some babies cry at night because of gastroesophageal reflux, where stomach contents flow back up into the esophagus. Signs that reflux might be the issue include arching of the back during or right after eating, frequent or forceful vomiting, gagging, refusing to eat, poor weight gain, and wheezing or trouble breathing. The crying is often worst after feedings and when the baby is lying flat, which is why nighttime can be especially difficult.
Gas is another common culprit. If your baby pulls their legs up toward their belly, seems uncomfortable after eating, or passes gas frequently, trapped air may be the issue. Gentle leg bicycling, burping more frequently during feeds, and keeping your baby upright for 15 to 20 minutes after eating can help.
Room Temperature and Sleep Environment
Sometimes the fix is simple. A room that’s too warm or too cold will wake a baby. The recommended range is 68 to 78 degrees Fahrenheit. A low-speed fan can help keep air circulating. Dress your baby in one layer more than you’d wear comfortably in the same room, and skip heavy blankets, which are both a suffocation risk and a common cause of overheating.
Signs That Something More Serious Is Going On
Most nighttime crying is normal, but certain patterns deserve a call to your baby’s doctor. Contact them if your baby skips two or more feedings in a row, is unusually sleepy or hard to wake, seems floppy, or is crying significantly more than usual and can’t be calmed. Any fever in a baby under three months old warrants a call regardless of the temperature. For babies 3 to 6 months, call if the temperature reaches 100.4°F or higher, or if it’s lower but they seem sick. For babies 6 to 24 months, a fever above 100.4°F that lasts more than a day needs attention.
Watch for signs of dehydration: fewer wet diapers, fewer tears when crying, a dry mouth, or a sunken soft spot on the head. Repeated vomiting after feedings, diarrhea (more than three very loose stools), trouble breathing, or a rash that appears suddenly or blisters also warrant a call. If your baby’s skin or lips look blue, purple, or gray, if they have a seizure, or if their pain and fussiness keeps getting worse and nothing helps, seek emergency care immediately.