The earliest reliable signs of dehydration are dark yellow urine and passing urine less often than usual. In children, watch for fewer wet nappies, no tears when crying, a dry mouth, and unusual sleepiness or irritability. Get emergency care for confusion, fainting, no urine for eight hours, sunken eyes, rapid breathing, or an inability to keep fluids down.
Thirst is a late signal, not an early one — by the time you feel thirsty you are already behind. In Arizona that lag is the whole problem.
Why Arizona is different
In humid places you notice you are sweating, so you notice you need water. Here, sweat evaporates the instant it forms. You lose the same fluid — often considerably more — and get almost none of the feedback.
Add low humidity pulling moisture from every breath you take, summer temperatures well above body heat, and the number of people who move here or arrive for the season without having calibrated to any of it, and you have the conditions we see in our emergency room every summer.
Children are at higher risk than adults because they have a larger surface area for their body weight, sweat less efficiently, and often will not stop playing to drink. Older adults are at higher risk because thirst perception genuinely declines with age, and because diuretics and blood pressure medication increase fluid loss.
Signs in infants and young children
Children cannot tell you they are dehydrated, so you are reading the body instead.
Early or mild:
- Fewer wet nappies — fewer than six a day in an infant, or no urine in six to eight hours in an older child
- Dry mouth and lips, thicker saliva
- Unusual crankiness, clinginess, or fussiness
- Slightly less energy than normal; less interest in playing
- Fewer tears when crying
Moderate to severe — come in:
- No wet nappy for eight hours or more
- No tears at all when crying
- Sunken eyes, or a sunken soft spot on an infant’s head
- Skin that stays tented when gently pinched
- Unusual sleepiness, floppiness, or difficulty waking
- Rapid breathing or a fast heartbeat
- Cold, blotchy hands and feet
- No interest in drinking, or vomiting everything offered
- Fewer than three wet nappies in 24 hours
Any of the moderate-to-severe list in an infant under six months is an immediate visit, not a wait-and-see.
Signs in adults
Mild to moderate: dark yellow urine, urinating less often, dry mouth, thirst, headache, tiredness, dizziness on standing, muscle cramps, reduced concentration.
Severe — come in now:
- Confusion, disorientation, or slurred speech
- Fainting, or nearly fainting on standing
- No urine for eight hours, or very dark, strong-smelling urine
- Rapid heartbeat and rapid, shallow breathing
- Sunken eyes, skin that stays tented when pinched
- No sweating despite heat — a genuine emergency sign
- Seizure
- Unable to keep any fluid down
The urine colour check
The most practical test there is. Pale straw is well hydrated. Dark yellow means drink now. Amber or the colour of apple juice means you are significantly behind. Brown or cola-coloured urine, particularly after heavy exertion in heat, needs emergency assessment — it can indicate muscle breakdown affecting the kidneys.
Caveat: B vitamins turn urine bright yellow, and some medications change its colour. Judge the trend, not one reading.
When dehydration becomes heat illness
In Arizona, dehydration and heat illness usually arrive together, and the escalation is the thing to know.
Heat exhaustion — heavy sweating, cold clammy skin, weakness, nausea, headache, muscle cramps, dizziness. Act now: get into air conditioning or shade, lie down, elevate the legs, loosen clothing, sip cool fluids, apply cool wet cloths. If there is no improvement in 30 minutes, come in.
Heat stroke — call 911 immediately. Body temperature above 103°F (39.4°C), hot red skin that is often dry because sweating has stopped, a pounding rapid pulse, confusion, slurred speech, or loss of consciousness. This is life-threatening and damages organs. While waiting: move them somewhere cool, remove excess clothing, and cool them aggressively with wet cloths, a cool shower, or ice packs at the neck, armpits, and groin. Do not give fluids to anyone confused or unconscious — they can choke.
Rehydrating properly
Small and frequent beats large and hopeful. A tablespoon every ten minutes stays down; a full glass often comes straight back up.
Use an oral rehydration solution for children — Pedialyte or equivalent. This matters more than people expect: sports drinks have too much sugar and too little sodium, and the excess sugar can worsen diarrhoea and pull more water into the gut. Plain water alone is also not ideal for significant losses, because it does not replace sodium.
Ice lollies and ice chips are often accepted by a child who refuses a cup.
Keep breastfeeding or formula-feeding infants, more often in smaller amounts.
For adults, water is fine for mild cases; add electrolytes after heavy sweating or if you have been vomiting or have diarrhoea.
Avoid alcohol and large amounts of caffeine while rehydrating, and skip salt tablets, which can make things worse.
Preventing it here
- Drink before you are thirsty, on a schedule rather than on sensation
- Carry water everywhere — the car, the golf cart, the trail, the school bag
- Start every hike already hydrated, and carry considerably more water than feels necessary. Rescues on the McDowell trails happen most often to people who brought one bottle.
- Avoid outdoor exertion between 10am and 4pm in summer
- Dress in light, loose, light-coloured clothing and a wide-brimmed hat
- Set a timer for children at play — they genuinely will not stop to drink
- Check on older neighbours and relatives during heat events, particularly if they are on diuretics
- Never leave anyone — child, adult, or pet — in a parked car, even briefly. Interior temperatures climb far faster than people believe.
What we can do
At our Emergency Room, significant dehydration is one of the most satisfying things we treat, because people feel better fast:
- Intravenous fluids with the right electrolyte balance
- Anti-sickness medication by injection when nothing will stay down
- Blood tests on site — sodium, potassium, kidney function, blood sugar, and markers of muscle breakdown
- Active cooling for heat illness
- Paediatric assessment by emergency physicians who treat children routinely
For recurring dehydration, medication review, or a child who is repeatedly unwell in the heat, our Medical Clinic is the right place: (602) 671-7981.
Where to go
Call 911 for confusion, fainting, seizure, a temperature above 103°F with hot dry skin, or an infant who is floppy and difficult to wake.
Come to our Emergency Room — 9700 N. Saguaro Blvd, open 24 hours, no appointment — for no urine in eight hours, an inability to keep fluids down, sunken eyes, or any moderate-to-severe sign above. ER: (602) 671-7990.
Related reading
- Heat Exhaustion or Heat Stroke? The Difference That Saves Lives
- When Nausea and Vomiting Become an Emergency
- Severe Abdominal Pain: When It’s More Than a Stomach Ache
Sources
- CDC — Heat-related illness: warning signs and symptoms
- American Academy of Pediatrics / HealthyChildren.org — Dehydration in children
- Mayo Clinic — Dehydration
- Arizona Department of Health Services — Extreme heat