A thirst for knowledge; a thirst for power; people get thirsty for lots of things. But that's not surprising when you consider that our bodies are between 50 percent (women) and 65 percent (men) water.

And that’s why it's so important to stay hydrated.

Yet dehydration can happen to almost anyone, at any time of the year, whether or not they're playing sports or working out. It hits when you lose more than 2 percent of your body weight through a water deficit.

The signs are thirst (if you're working out, drink before thirst sets in) and cold legs (especially if you're not working out) progressing to dark urine, dizziness, cramps, constipation, headache, and flaky skin.

While it can knock anyone off his or her feet — and into the emergency room — it's especially a concern for those who work out or avoid drinking water and older folks, who may forget to drink water regularly.

Dehydration can upset the sodium/water balance in your blood and body, and that destabilizes your heartbeat (your heart is 73 percent water) as well as the health of your muscles (75 percent water), brain, and all other organs.

How much water does it take to stay hydrated? The Institute of Medicine of the National Academies says thirst can be your guide, but about 91 ounces of water daily (80 percent from drinking; 20 percent from foods) should be enough for women; 125 ounces a day for men.

Those who live in hot climates or exercise may need more.