how to tell if my baby is overtired vs undertired

How Do I Tell if My Baby is Overtired vs. Undertired? Learn to Tell The Difference and Strategies to Help Your Baby’s Sleep

Understanding your baby’s sleep is the foundation to being able to support it in a way that allows your baby (and you) to get the best sleep possible. Figuring out how to tell if your baby is overtired or undertired, in a common challenge. This is an important question because having your baby in an ideal sleepy zone is key to them being able to fall asleep and stay asleep most easily.

In this comprehensive guide, we’ll explore what to look for to determine if your baby is overtired or undertired and strategies you can use to address either situation.

(Skip down to strategies for overtiredness and undertiredness now!)

Overtired vs. Undertired: What’s the Difference?

Before diving into how to recognize if your baby is overtired or undertired, let’s clarify what overtired versus undertired means.

  • Overtired: This is when a baby has stayed awake through their natural sleep window. Their body compensates with stimulating hormones like adrenaline and cortisol to help keep them awake. These hormones make it harder to fall and stay asleep.
  • Undertired: When we are awake and using energy, the neurotransmitter adenosine is building up in our brains. [I] Adenosine increases our need to sleep, or our sleep pressure. This basically is how tired we feel. If not enough adenosine has built up, it will be more difficult to fall asleep, leading to being undertired.

Wake Windows and Overtiredness or Undertiredness

A wake window is the amount of time your baby is awake between daytime sleep periods and before bedtime. Because both overtiredness and undertiredness are influenced by time, determining the appropriate wake windows for your baby is important for helping your baby be able to get to sleep in their ideal sleepy window. This is the time when they can most easily fall asleep because their sleep pressure is high enough but they have not crossed into overtiredness yet.

As your baby gets older, their wake windows naturally increase. Additionally, wake windows tend to increase throughout the day with the first wake window being the shortest. Here are average wake windows by age:

baby wake windows by age to prevent overtiredness and undertiredness

Keep in mind that these are averages, not hard and fast rules. The more alert and active we are, the faster adenosine builds up in our brain.[2] This leads to babies (and all humans) getting sleepy sooner. Especially after they have done some extra activity or something with lots of new and exciting stimuli which generally requires babies to be more alert and use more energy as they take in everything new.

Learning and watching for sleepy cues is a good way to understand, on average, how long your baby’s wake windows should be throughout the day.

Baby Sleepy Cues

When working to decode and learn your baby’s sleepy cues, try to look for early sleepy cues versus late sleepy cues. Late sleepy cues show that a baby has already gotten pretty far into their ideal sleep window. So you need to act fast to help or allow your baby to fall asleep. Some examples of late sleepy cues include: getting really fussy or inconsolable, rubbing eyes, yawning, and fussy eating/not really wanting to eat.

Earlier sleepy cues start happening as your baby is approaching or in the beginning of their ideal sleep window. Some examples include: Staring off, not interested in play, turning away from stimuli, and red eyebrows.

Observe your baby for a week or so towards the beginning of the range of the average wake window for their age to see what their unique early sleep cues are. The examples above are not all encompassing of sleepy cues you may see with your baby so keep an open mind about what you are seeing your baby do.

Pro Tip: Use the average wake window for your baby’s age to know when to start looking for sleepy cues. If you are trying to look during your baby’s entire wake window it may become confusing. Some cues that mean “I’m getting sleepy” after the 2 hour mark, may mean “I need a change of scenery” when your baby has only been awake for 1 hour.

Signs of an Overtired Baby

Recognizing when your baby is overtired will allow you to avoid getting into a cycle with their overtiredness so that they can get the best sleep possible. Here are some signs to look for:

  • Irritable: Overtired babies tend to be fussier and more difficult to soothe. Sometimes babies are inconsolable.
  • Difficulty Falling Asleep/Fighting Sleep: Your overtired baby may struggle to fall asleep despite showing clear signs of tiredness. (This is because of the stimulating hormones that flooded their system to give them a second wind, which makes it harder to fall asleep.)
  • Becoming ‘wired’: Because baby sleep is often counterintuitive, some overtired babies (especially older babies) become hyperactive or “wired” due to fatigue. Often they will seem tired and then all of a sudden, they start acting hyper and wired.
  • Fussy/frustrated eating: It will seem like your baby wants to eat, but will take a little from the breast or bottle and then get frustrated and pull away. 
  • Short naps, increased night wake ups, early morning wake ups: Overtired babies often take shorter naps, wake more frequently during the night and waking up earlier in the morning when sleep is lighter and sleep pressure has been depleted.
  • False starts: Your baby wakes up 30-60 minutes, approximately one sleep cycle, after going to bed at night.

What Does Undertiredness Look Like for a Baby?

Recognizing if your baby is undertired is equally important as recognizing overtiredness. Here are signs to look for to determine if your baby may not be tired enough for quality sleep:

  • Alertness: They may remain alert and attentive even when it’s time for sleep. You don’t see any sleepy cues when you think they should be ready for sleep.
  • Difficulty Falling Asleep: As opposed to overtired babies, undertired babies may struggle to fall asleep because they haven’t accumulated enough sleep debt. They may roll around contently for over 20 minutes until they fall asleep, or they may seem frustrated when they know you are getting them ready for sleep since they don’t want to go to sleep yet because they do not feel tired enough.
  • Your baby wants to ‘party’ in the middle of the night: An undertired baby might wake up during the middle of the night and be wide awake and ready to go for an hour or more! 
  • Short Naps: Your baby may take short naps during the day because they haven’t built up enough sleep pressure. After one sleep cycle, their sleep pressure is depleted and they are not able to connect sleep cycles. Often with undertired babies’ short naps they wake up happy or content and seem refreshed.

Strategies for Breaking the Cycle of an Overtired Baby 

Once you know that your baby is overtired vs. undertired, start to address the overtiredness. Otherwise, it can become a cycle that goes on and on, and seemingly gets worse. Here are some strategies to break the cycle of an overtired baby:

  • Establish Consistent Sleep Routines: Create calming nap and bedtime routines to signal to your baby that sleep is coming. When certain steps are done in a certain order, it helps their brains and bodies more easily transition to sleep. Falling asleep after can help avoid perpetuating the cycle.  
  • Watch for sleepy cues: Watch for your baby’s sleepy cues a bit earlier than you normally would so that you can catch your baby’s signs right when they are getting into their ideal sleep window. The goal is to get your baby to sleep before another second wind kicks in. This may mean your baby is going to bed early for a few nights.
  • Avoid Overstimulation: Limit exposure to bright lights, loud noises, and excessive playtime, especially close to bedtime. This can be a lot for their brains to handle and process and can lead to missing your baby’s sleep window.
  • Keep the sleep environment dark: Darkness cues our bodies’ circadian rhythm at night that it is time to sleep, but it also limits visual stimulation so your baby can focus on sleep. 
  • Take 2-3 days to reset: Have a few calm days at home. Focus on sleep so you can catch your baby’s sleepy signs quickly.
  • Consolidated sleep: When your baby connects more than one sleep cycle, they are consolidating their sleep. This can be more refreshing and restorative than disrupted sleep. For example, when your baby wakes up from their 30-45 minute nap grumpy compared to a better mood when they take a longer nap.

3 Tips for Supporting an Undertired Baby 

When dealing with an undertired baby, the goal is to help them accumulate enough sleep pressure to they can fall asleep and stay asleep easily. Here are some strategies to try:

  • Encourage more active play: Active play and movement help to expend energy. The more energy used, the more adenosine is released, helping your baby feel tired and ready to sleep. As your baby gets older, they need more active play and movement to feel tired enough for sleep.
  • Maintain a consistent routine or schedule: This starts with waking your baby at about the same time each day. This sets their schedule for the day and allows for a consistent bedtime. Regular morning wake up and bedtimes help keep the sleep-wake cycle regulated.
  • Monitor and Increase Wake Windows as Needed: As your baby grows, their wake windows will increase too. Keep track of when your baby’s sleepy signs are happening, when you stop seeing sleepy signs around bedtime, you can wait a little longer before attempting sleep. Additionally, if your baby is happily taking over 20 minutes to fall asleep, or seems frustrated for over 20 minutes before falling asleep, start to increase their wake windows by about 15 minutes or so until they get back to falling asleep and staying asleep.
what does undertired look like baby wakes up happy from short nap

Common Questions When Your Baby May Be Overtired vs Undertired

Do Short Maps Mean Overtired or Undertired?

Unfortunately for this one, the answer is that it could be either. When a baby is overtired and they wake up from a short nap of 30-50 minutes, or one sleep cycle, they often seem still tired and fussy. Whereas an undertired baby often wakes up from a short nap feeling content and refreshed. (Here are 7 troubleshooting tips for short naps!)

Why is my Baby Yawning 30 Minutes After They Wake Up?

As humans, we yawn for lots of different reasons. For example, it can help to reset your brain after being overstimulated. While yawning is a sleepy cue, if your baby woke up 30 minutes ago, enough time has not passed for enough sleep pressure to have built up to help them connect sleep cycles. (If you have a newborn younger than 8 weeks, wake windows may only be 30 minutes long but newborns don’t really show reliable sleepy cues!) In this case, the yawn may be trying to tell you something else.

Learning to Tell The Difference Between Overtiredness and Undertiredness

Learning how to recognize if your baby is overtired or undertired is a valuable skill for parents, as it can help everyone get the best quality of sleep possible. Decoding your baby’s sleepy cues as well as being aware of signs of overtiredness compared to what undertiredness looks like, you can help your baby get the best sleep possible.

If you are struggling with your baby’s sleep and can’t seem to figure out if it is overtiredness or undertiredness or something else completely that is keeping your baby (and you!) from getting good sleep, reach out. It does not have to remain an overwhelming and confusing mystery. Schedule your free sleep evaluation call with Bonnie, Baby and Toddler Sleep Coach! We will chat through what is going on, what factors may be contributing to the struggles and how I can help you resolve those so you can all get the sleep  you need while feeling empowered to support your baby’s sleep long term!

Cheers to healthy, happy sleep,


Learn more about Bonnie and how she works with families to get everyone sleeping better here.



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