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  • Writer's pictureAlan Frischer, MD, MPH


I am always reminding my patients to drink more water. While there are a few disease conditions where people must watch their fluid intake, most people simply do not drink enough. Dehydration can have serious physical consequences.

When dehydrated, the body lacks enough water to function properly. We have water inside our cells, within blood vessels, and between cells; in fact, water makes up approximately 75% of the human body. A sophisticated water management system keeps water levels balanced, and our thirst mechanism usually tells us when we need more fluid.

Water loss is natural. We lose water from sweating, breathing, urinating, bowel movements, tears and saliva. Dehydration is caused either by losing too much fluid, by not drinking enough to replace what is lost, or both. Additional fluid is lost from a fever, diarrhea, vomiting, excessive sweating, excess urination as a result of diabetes, diuretic medicine, or to some extent by consuming diuretics like alcohol or caffeine.

Outdoor work or exercise, especially in heat, increases the risk of dehydration, and when the air is humid, sweat doesn’t evaporate and cool the body as quickly as usual. This leads to an increased body temperature and the need for more fluids.

Many people choose not to drink in order to avoid having to get up to urinate. The elderly often make this conscious choice, as do those whose jobs make it difficult to take bathroom breaks.

Older adults are at greater risk for dehydration. They have smaller body fluid reserves. The ability to conserve water is reduced and the thirst sense becomes less acute. Compounding the problem, the elderly may suffer from chronic diseases like diabetes or dementia. They could be on medications that cause fluid loss. They may have chronic kidney disease or heart failure, which would require that they consume less fluid. Older adults also may have mobility problems that limit their ability to get water to drink, or to reach a bathroom.

Signs of dehydration include thirst, dry or sticky mouth, decreased urination and dark yellow urine, dry, cool skin, headache, and muscle cramps. Signs of severe dehydration include infrequent and dark urine, very dry skin, dizziness, rapid heartbeat, rapid breathing, sunken eyes, sleepiness, lack of energy, confusion or irritability, and even fainting. Severe dehydration is a medical emergency that requires immediate attention.

Dehydration can lead to urinary and kidney problems which include urinary tract infections, kidney stones and kidney failure. It can cause electrolyte imbalances; electrolytes carry electrical signals from cell to cell, and an imbalance can lead to involuntary muscle contractions and even seizures. Low blood volume from dehydration can cause a drop in blood pressure, a drop in oxygen in the cells, and most severely, hypovolemic shock.

Always drink plenty of fluids, and eat foods with high water content, like fruits and vegetables. Most healthy people can let thirst be their guide. Note the frequency, quantity and color of your urine. Pay extra attention to hydration if you are strenuously exercising, or are experiencing vomiting, diarrhea, or other illness. If you have had diarrhea for more than 24 hours, can’t keep fluids down, or show any of the signs of serious dehydration, call your doctor immediately.

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