Signs of Dehydration: What to Look For and What to Do

Signs of dehydration in adults

Mild to moderate

• thirst and a dry, sticky mouth
• dark yellow, strong-smelling urine, and peeing less often (fewer than about 4 times a day)
• tiredness and low energy
• headache and poor concentration
• dry lips and skin
• muscle cramps
• constipation

Severe

• dizziness or light-headedness, especially on standing
• a rapid heartbeat and fast breathing
• very little or no urine
• sunken eyes
• confusion, irritability or drowsiness
• low blood pressure and fainting

Thirst is a late signal in older adults, and urine color is a better everyday check: pale straw-colored urine means you are drinking enough.

Signs of dehydration in babies and children

Babies and toddlers lose fluid fast because of their small size and high turnover. Look for:

Signs of dehydration in older adults

Older people feel less thirsty, their kidneys conserve water less well, and they may limit drinking to avoid trips to the toilet. Dehydration may show up only as new confusion, falls, dizziness, constipation or a urinary tract infection. Diuretics ("water pills") and laxatives add to the risk.

Does persistent vomiting cause dehydration?

Yes. Persistent vomiting is one of the fastest routes to dehydration, because you lose fluid and salts while being unable to keep drinks down. It also causes low potassium and other electrolyte problems. Warning signs that vomiting is causing dehydration:

• you cannot keep down even small sips for more than 6 to 8 hours
• urine becomes dark or stops
• you feel dizzy, weak or confused

Vomiting combined with diarrhea, as in gastroenteritis, dehydrates even faster. Other causes of persistent vomiting, such as pregnancy sickness (hyperemesis gravidarum), migraine, bowel obstruction or diabetic ketoacidosis, need medical care in their own right.

Common causes

• vomiting and diarrhea
• fever, which increases fluid loss through the skin and breathing
• heavy sweating from heat, exercise or physical work. See heat exhaustion
• not drinking enough, because of illness, sore throat, confusion or limited access to water
• high blood sugar, which pulls water into the urine
• medicines such as diuretics and laxatives
• alcohol, which increases urine output
• burns, which leak fluid through damaged skin

What to do if you are dehydrated

Mild dehydration

1. Drink little and often. Take small sips every few minutes rather than large gulps, especially if you feel sick.
2. Use oral rehydration solution (ORS) for dehydration from vomiting or diarrhea. It contains the right balance of salts and sugar to be absorbed quickly. Plain water is fine for mild dehydration from heat or exercise.
3. Avoid very sugary drinks, undiluted fruit juice and energy drinks, which can worsen diarrhea, and alcohol.
4. Rest in a cool place.
5. Check your urine: it should become paler and more frequent within a few hours.

Babies and children

• Keep breastfeeding, offering feeds more often.
• For formula-fed babies and children, give ORS in small amounts, for example 1 to 2 teaspoons (5 to 10 ml) every few minutes using a spoon or syringe, increasing as tolerated.
• Do not give plain water alone to babies under 6 months, and do not dilute formula.
• Resume normal food once vomiting settles.

When home treatment is not enough

Severe dehydration needs medical treatment, often with IV fluids. Some people with moderate dehydration who cannot keep fluids down benefit from anti-nausea medicine in urgent care. More on the medical side, including electrolyte problems and complications, is on the dehydration condition page.

Frequently asked questions

What are the first signs of dehydration?

The first signs are usually thirst, a dry mouth, dark yellow urine and peeing less often. Tiredness, headache and difficulty concentrating often follow. In babies, fewer wet diapers and fewer tears are early clues.

Does persistent vomiting cause dehydration?

Yes. Ongoing vomiting quickly removes fluid and salts and makes it hard to replace them. If you cannot keep down any fluid for 6 to 8 hours, or 4 hours for a baby, or you develop dizziness or stop passing urine, seek medical care.

How can I tell if I am dehydrated?

Check your urine: dark yellow urine and peeing less than usual are reliable signs. Other clues are thirst, a dry mouth, headache, tiredness and feeling dizzy when you stand up. Pale yellow urine usually means you are well hydrated.

How long does it take to recover from dehydration?

Mild dehydration usually improves within a few hours of drinking enough fluid. Moderate dehydration can take a day or so to correct. Severe dehydration may need IV fluids in the hospital, with recovery over 1 to 2 days once the cause is treated.

What is the fastest way to rehydrate?

For mild dehydration from exercise or heat, water works well. After vomiting or diarrhea, oral rehydration solution rehydrates fastest by mouth because its salt and sugar balance helps the gut absorb water. Severe dehydration is fastest treated with IV fluids.