Overview
Dehydration happens when you lose more fluid than you take in. Your body also loses salts called electrolytes. It can be mild, moderate, or severe.
Babies, young children, and older adults get dehydrated most easily. If you treat it early, you should recover fully.
Symptoms
Signs depend on how much fluid is lost.
- Thirst
- Dark yellow urine
- Peeing less than usual
- Dry or sticky mouth
- Headache
- Dizziness
- Fatigue
Less common
- Muscle cramps
- Dry, cool skin
- Muscle weakness
- Fast heartbeat or fast breathing
- Sunken eyes
- Confusion or fainting
How it usually goes
- Mild: Thirst, dark urine, and dry mouth.
- Moderate: Headache, dizziness, muscle cramps, and much less urine.
- Severe: Confusion, fast heartbeat, no urine, or fainting. This is an emergency.
When to get medical care
Causes
Dehydration can come from diarrhea, vomiting, fever, heavy sweating, or not drinking enough. Peeing too much from some medicines or high blood sugar can also cause it.
Being sick with a sore throat or nausea can make it hard to drink enough.
Does it spread or run in families?
- It isn't contagious. You can't catch it from someone else.
Who is more likely to get it
- Babies and young children
- Older adults, who may not feel thirsty
- Long-term illnesses, like diabetes or kidney disease
- Working or exercising in the heat
Possible complications
- Heat exhaustion: Heat illness from fluid loss
- Heatstroke: A life-threatening heat emergency
- Kidney stones: More likely when you don't drink enough
Diagnosis
A healthcare professional can usually tell from your symptoms and an exam.
Questions you may be asked
- How much you've been drinking and peeing
- Vomiting, diarrhea, fever, or heavy sweating
- Medicines you take, like water pills
- Time in the heat or exercise
The exam
They'll check your blood pressure and heart rate, look at your mouth and eyes, and pinch your skin to see how fast it springs back.
Tests
For moderate or severe cases:
- Blood tests: To check salt levels and how well your kidneys are working.
- Urine test: To see how concentrated your urine is.
Treatment
Treatment replaces the fluids and salts you've lost.
Self-care
- Sip water often, or suck on ice chips if you feel sick
- Drink an oral rehydration solution or sports drink if you've lost salts from vomiting, diarrhea, or sweating
- Give children oral rehydration solution, a little at a time
- Rest in a cool place
- Don't take salt tablets. They can cause serious problems
- Avoid alcohol and lots of caffeine
Medicines
No medicine treats dehydration itself. These help replace fluid.
| Medicine | Helps with | Good to know |
|---|---|---|
| Oral rehydration solution | Replacing water and salts, especially in children | Don't add extra water to ready-made drinks. Mix powders exactly as the label says. |
| Sports drinks | Mild fluid and salt loss in adults | High in sugar. For children with diarrhea, oral rehydration solution is better. |
If you take water pills (diuretics) or certain blood pressure medicines and get sick with vomiting or diarrhea, call your healthcare professional.
Severe dehydration is treated in a hospital with fluids through a vein (IV). Your healthcare professional will also treat the cause, such as an infection or heat illness.
How it compares
| Dehydration | Heat exhaustion | Heatstroke | Stomach bug | |
|---|---|---|---|---|
| Main signs | Thirst, dark urine | Heavy sweating, cool skin | Hot skin, confusion | Vomiting, diarrhea |
| Urgency | Usually home care | Cool down now | Call 911 | Usually home care |
| Main treatment | Fluids with salts | Cool place, sip water | Emergency cooling | Fluids and rest |
Prevention
You can prevent most dehydration:
- Drink fluids every day, and more in hot weather or when active
- Start extra fluids as soon as someone has fever, vomiting, or diarrhea
- Watch children and older adults closely when they're sick
- Keep oral rehydration solution at home
Which doctor treats this
- Start with your primary care provider (family doctor or internist).
Back to school, work, or sports
- Most people keep up normal school and work. Rest when you need to.
Children, pregnancy, and older adults
- Babies and children: Watch for no tears, a dry mouth, fewer wet diapers, and unusual sleepiness. Keep breastfeeding. Call for any signs of dehydration.
- Older adults: They may not feel thirsty. Offer drinks often.
- Pregnancy: Severe morning sickness can cause dehydration. Call if you can't keep fluids down.
Pregnancy and breastfeeding
- If you're pregnant or planning to be, tell your prenatal provider about this condition.
- Don't start or stop any medicine on your own. Some are safe in pregnancy and some need to be changed.
- Ask before taking any pain reliever. The FDA advises avoiding ibuprofen and naproxen after 20 weeks unless your doctor says to.
- Breastfeeding: Most medicines are fine, but ask. The NIH LactMed database lists what's known about each one.
Outlook
Mild dehydration gets better quickly with fluids. If you notice signs early and treat them, you should recover completely.
Getting ready for your visit
Keep track of what goes in and out.
What to bring
- How much you've been drinking
- How often you've peed, vomited, or had diarrhea
- A list of your medicines
Questions to ask
- What's causing this?
- Do I need IV fluids?
- How much should I drink, and what?
- Should I change any of my medicines while I'm sick?
Research studies
Research studies test new ways to find and treat health problems. Some are looking for volunteers. Talk with your doctor before joining one.
Sources
Last updated 2026-11-12.