Kaiser Permanente nephrologist Steven Guest, MD, agrees: "Fluid losses occur continuously, from skin evaporation, breathing, urine, and stool, and these losses must be replaced daily for good health," he says.
When your water intake does not equal your output, you can become dehydrated. Fluid losses are accentuated in warmer climates, during strenuous exercise, in high altitudes, and in older adults, whose sense of thirst may not be as sharp.
Here are six reasons to make sure you're drinking enough water or other fluids every day: