Recognizing signs of dehydration is important. They include:

• Little or no urine.
• Urine that is darker than usual.
• Dry mouth.
• Sleepiness or fatigue.
• Extreme thirst.
• Headache.
• Confusion.
• Dizziness or lightheadedness.
• No tears when crying.

Don’t wait until you notice symptoms of dehydration to take action. Actively prevent dehydration by drinking plenty of water.

Some people are at higher risk of dehydration, including people who exercise at a high intensity (or in hot weather) for too long, have certain medical conditions (kidney stones, bladder infection), are sick (fever, vomiting, diarrhea), are pregnant or breastfeeding, are trying to lose weight, or are not able to get enough fluids during the day. Older adults are also at higher risk. As you get older, your brain may not be able to sense dehydration. It doesn’t send signals for thirst.

Water makes up more than half of your body weight. You lose water each day when you go to the bathroom, sweat, and even when you breathe. You lose water even faster when the weather is really hot, when you are physically active, or if you have a fever. Vomiting and diarrhea can also lead to rapid water loss. If you don’t replace the water you lose, you can become dehydrated.