Undertired vs. Overtired: How to Tell Why Your Baby Is Fighting Sleep
If your baby resists naps or bedtime, you might immediately assume they're overtired. But what if the real problem is the opposite?
As a pediatric sleep coach, I’ve seen countless families struggle to decode their baby’s behavior before sleep. The truth is - undertired and overtired babies often look like they’re doing the same thing: crying, playing, or refusing to settle. But the why behind it is very different.
Knowing the difference helps you adjust your schedule and set your baby up for easier naps and longer stretches of sleep.
Signs Your Baby Is Undertired
An undertired baby simply isn’t ready to sleep yet. They’re still in a good mood and don’t have enough sleep pressure built up.
Here’s how to spot it:
Before nap: Happy, playful, no tired cues like yawning or rubbing eyes. Resists sleep by babbling, laughing, or rolling around.
During nap: Takes 15–30+ minutes to fall asleep without crying at the onset. Short nap (30–45 mins), wakes up alert.
After nap: Wakes in a good mood, ready to play
What to do: Try extending their wake window by 5 minutes every 2-3 days.
Signs Your Baby Is Overtired
An overtired baby has been awake too long and is running on stress hormones like cortisol, which makes it harder to settle, even when exhausted.
Watch for these signs:
Before nap: Cranky, clingy, or wired; strong cues like fussing or zoning out. Resists nap with intense crying or meltdowns.
During nap: Takes a long time to fall asleep due to overstimulation. Intense crying as soon as placed in bed. Short or fragmented nap, multiple wake-ups and tears.
After nap: Wakes up crying or fussy, harder to resettle.
What to do: Try an earlier nap or bedtime, even by 15 minutes. Shorten wake windows by 5 minutes every 2-3 days to help your baby avoid crossing into overtired territory.
Still Not Sure Which It Is?
That’s completely normal, especially if you didn’t see when your baby woke up from a nap or in the morning.
In those moments, observe your baby’s behavior closely. Are they calm and chatty, or fussy and restless? A log of sleep times, behaviors, and how long it takes to fall asleep can help reveal patterns over time. You’ll know you found the sweet spot when your baby is able to fall asleep within 10 minutes on their own with minimal crying (some fussing might still happen, but it will stop after 5-10 minutes).
Need a Hand?
I help exhausted parents get their babies sleeping independently in as few as 3 nights. If you’re stuck in the overtired–undertired cycle and don’t know what your baby actually needs, let’s build a custom plan together. You don’t have to figure this out alone.
