People suffer dehydration when they do not consume sufficient amounts of water to replace the fluids that their bodies lose, explains Mayo Clinic. Some people do not drink enough water because they are too busy or feel ill, while others do not have accessible sources of safe water, especially when traveling outdoors. Frequent urination, too much sweating, fever and severe diarrhea with vomiting are also possible causes of dehydration.
Severe, acute diarrhea causes a person to lose significant amounts of water and electrolytes in a brief period, states Mayo Clinic. When it occurs with vomiting, a person loses more fluids. Bowel disorders, side effects of medications, sensitivity to certain foods, and bacterial and viral infections can lead to diarrhea. More frequent urination than normal indicates uncontrolled or undiagnosed diabetes. Medications that cause a person to urinate or sweat too much may also cause dehydration.
People with fever experience worse dehydration when their temperatures rise, according to Mayo Clinic. Dehydration aggravates if the fever occurs with accompanying symptoms, such as diarrhea and vomiting. Engaging in strenuous activities, especially in hot weather, without replenishing the body's water supply also leads to dehydration.
Patients with chronic sicknesses, older people and children are vulnerable to dehydration, notes Mayo Clinic. It helps to drink more water to treat mild dehydration. Serious dehydration requires prompt medical care.