How to tell if your child is dehydrated

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Very often, pediatricians tell parents to “watch for dehydration” without making clear what to watch for. So here is a practical post that tells you exactly what to pay attention to if you’re worried about dehydration.

Because dehydration can go from mild to severe quite quickly in a child, I always recommend giving your pediatrician a call first to discuss your specific situation, what red flags to watch for, and how to proceed.

Dehydration is a math problem

Dehydration can happen because of illness, over-exertion, or the environment.

Think about fluid status is as an equation between fluid in and fluid out. Anything that changes either one of these factors will lead to an imbalance.

For example:

• Intake: Can decrease if a child is refusing fluids (eg. if they have a sore throat and don’t want to drink) or doesn’t think to drink (eg. they’re having fun at the beach and no one reminded them!)

• Output: Can increase if there is vomiting or diarrhea, or increased sweating (eg. due to physical exertion, a hot environment, or even fever).

What signs should I watch for?

If you suspect your child might be dehydrated, pay special attention to the following:

• Lips and mouth

  • Lips and mouth get tacky or dry or (for younger babies) they drool less

  • For younger infants and toddlers, they may cry with fewer (or no) tears.

• Eyes and head

  • Eyes start to look sunken

  • Fewer (or no) tears when they cry

  • Fontanelle (soft spot on scalp) starts to look sunken

  • Complaints of headache or dizziness in older children

• Urine output

  • If their pee is darker yellow than usual, or less frequent, this may signal early dehydration.

    • Infant under 1 year: fewer than 6 wet diapers in a 24h period.

    • Toddler/child: not peeing at least once every 8 hrs

• Behavior and other clinical findings

  • Act more tired or irritable

  • Very thirsty

  • Muscle cramps

  • Breathing and heart rate are more rapid

  • Blotchy or mottled skin

  • Clinicians will also check capillary refill time: this involves pressing the fingernail or toenail until it becomes pale, and then counting how many seconds until the color returns (<3 seconds is normal). Note: this is included for interest, but in general if a child has delayed capillary refill, you should already have spoken with your doctor!

What to do if your child is dehydrated

Check out this post for practical tips for what to do if your child is dehydrated.

Figuring out if your child is dehydrated is something you would think was super easy, but like with so many things in parenting, things aren’t always so black-and-white. In general, I recommend erring on the side of caution: if you’re concerned, it is always better to seek care than to wait it out. But I hope this post made it a little easier!