Signs of Dehydration — Checklist for Adults and Kids

Check the signs you have right now. The score is an orientation, not a diagnosis — and the last item on the list is a red flag on its own, not a point to add up.

Adult signs, in the order they appear

StatPearls sets out the adult progression clearly. Early: increased thirst, dry mouth, weakness, and decreased urine output. As it worsens: dizziness, muscle weakness, palpitations, confusion and irritability.

On examination, moderate-to-severe dehydration shows decreased skin turgor and dry mucous membranes, with tachycardia, hypotension on standing and delayed capillary refill indicating reduced blood volume. Dark-colored urine and oliguria are frequent. Severe cases can present with confusion, lethargy or coma, and can progress to shock — profound low blood pressure, cool clammy skin, poor perfusion of vital organs.

Two things are worth pulling out of that list.

Urine is the cheapest instrument you have. Pale yellow across the day is on target; persistently dark yellow with few bathroom trips is not. As a clinical anchor, adequate hydration corresponds to a urine output of at least 0.5 mL per kg per hour.

Thirst lags. It rises as body mass losses approach about 2%, which means you have already been running a deficit before you notice. Muscle cramps, weakness and an increased risk of falls belong on the list too — fluid and electrolyte imbalance produces all three, especially in older adults.

Children and babies

Children dehydrate faster than adults, carry a higher share of body water, and often will not stop playing to say they are thirsty. The AAP’s lists:

Infants — fewer wet diapers than the typical six to eight; overly sleepy; sunken soft spot (fontanelle); no tears when crying. If you are worried an infant is not getting enough to drink, the advice is to call the pediatrician immediately.

Older children — dry lips or sticky mouth; less urination or dark-colored urine, when it should be very light yellow and almost clear; sleepy and irritable; flushed skin.

Teens — dry lips or mouth, lightheadedness, cramps, thirst, dark or reduced urine, headache, rapid pulse, flushed skin, feeling excessively hot or cold. Risk climbs with high-intensity workouts and heavy practices, and climbs further in hot weather.

StatPearls grades pediatric dehydration by weight loss: mild at 3% to 5%, moderate at 6% to 10%, severe above 10%. Mild may show nothing but reduced urine output. Dry oral mucosa, poor skin turgor, prolonged capillary refill, fast heart rate and irritability mark moderate. Children with severe dehydration look plainly ill — altered mental status, lethargy, rapid breathing, low blood pressure, mottled skin. Hypotension and shock are late signs.

Who gets there first

• Older adults. Thirst blunts with age and the kidney concentrates urine less well, so dehydration develops quietly. See how much water should seniors drink.
• Young children, for the reasons above, especially with fever, vomiting or diarrhea.
• Anyone in heat or training. Sweat accelerates everything — how much water to drink in hot weather covers the add-on.
• People with diabetes, kidney disease or heart failure, and anyone taking diuretics.

How much you might be short

If the checklist points to a deficit, compare what you actually drink against a target for your body size:

Weight	Daily target	If you drink 1.5 L, short by…
132 lb (60 kg)	2.10 L	~0.6 L
154 lb (70 kg)	2.45 L	~0.95 L
176 lb (80 kg)	2.80 L	~1.3 L
198 lb (90 kg)	3.15 L	~1.65 L

The daily water intake calculator gives your exact figure.

Fixing it, and when not to try

Replace steadily rather than all at once. The kidney’s maximum excretion rate is only about 0.7 to 1.0 liters an hour, so a large fast volume mostly becomes urine — and, in the extreme, dilutes blood sodium.

Where the losses came from vomiting or diarrhea, salts left with the water, and plain water alone can make the electrolyte picture worse. Oral rehydration solution is the appropriate replacement there. StatPearls’ pediatric guidance is to give it in small amounts frequently — around 5 mL every one to two minutes — because volume delivered slowly is tolerated where a glass is not.

Stop treating it at home if there is confusion, marked drowsiness, a racing heart, low blood pressure, or no urine for many hours; in a child, a sunken fontanelle or no tears when crying. Those are signs that fluid needs to go in under supervision.

This is an orientation tool, not a diagnosis. Persistent or severe symptoms should be assessed by a clinician.