Distinguish between a simple water loss and dehydration?

Answer 1

Simple water loss could be, for example, a healthy person exercises at the gym. She sweats but as she works out, she drinks water. Drinking replaces the water loss from sweating.

However, let's say her friend exercises, sweats, but does not drink water. After 3 hours at the gym, she walks home in the sun. She's thirsty but ignores her thirst because there's no where to stop and buy a drink. She starts to feel nauseous from the heat and lack of fluid. When she arrives home, she throws up because her stomach is reacting to low fluids plus overheating. Rather than get a drink, she lays down thinking her stomach will calm down if she rests. After a 2 hour nap, she awakens with her mouth dry, still nauseous. Technically, she could be mildly dehydrated.

Let's change the example again. We'll use an elderly person this time. The person can't get their own food and water because he is bedridden. The hired help gives him 1 4-ounce glass of water in the morning but another worker takes over in the afternoon; today, the 2nd person doesn't come. The old man is sweating (normal fluid loss) because it's an 80-degree day and he has no AC; the worker forgot to put the fan on. By evening when another worker arrives, she finds the apartment at almost 90-degrees inside, with no fan on, and no water left for the man. He is almost delirious. She calls an ambulance. The ER starts an IV and within hours (IF there was no other damage), the man is less confused. He was dehydrated.

Children, elderly, or people with illnesses are most at risk of dehydration. As we lose fluids naturally through sweat, saliva, urination and stool (especially diarrhea), we must replace those fluids, especially when it's hot or during exercise. But if young, old, or ill, we need to pay attention to fluid loss and fluid rehydration even more than if the person is a healthy teen or adult.