How Much Should You Drink?

We need water to keep our bodies functioning properly. But, as we get older, our thirst-response system diminishes and we may not feel thirsty even as dehydration sets in. Not drinking enough fluids can lead to

  • constipation
  • balance problems and falls
  • urinary tract infections
  • kidney failure
  • slower healing from wounds, ulcers and orthopedic injuries

How much water do we need? Contrary to popular belief, no research exists that says exactly how much fluid we should drink. However, many experts suggest that healthy adults should strive for six to eight 8-ounce servings of liquid a day.

Hydration can come from a variety of sources, including fruit or vegetable juice, nonfat milk, low-sodium soup, even coffee or tea. Many fruits and vegetables, such as watermelon, berries, grapes, peaches, tomatoes and lettuce, are almost 100 percent water. Even meat is chock full of water. Water from foods typically accounts for 20 percent of the recommended total fluid intake.

If you have kidney disease, diabetes or a thyroid disorder, you may be at higher risk for dehydration since these conditions can cause the body to excrete more water. Some people with heart, kidney or liver disease may be more likely to become over-hydrated because their kidneys can't excrete water normally. They may need to restrict the amount of fluids they drink and adjust their salt intake.

You may also be more prone to dehydration if you take certain medications. These include antihypertensives, such as diuretics and angiotensin-converting enzyme (ACE) inhibitors, and antipsychotic drugs and cholinesterase inhibitors, used to treat Alzheimer's disease and other dementia-related illnesses.

Instances in which you should increase your fluid intake beyond the suggested amounts include:

  • While you exercise. For an hour of light to moderate exercise, two to three cups of fluid are recommended for sufficient rehydration.
  • If it's unusually hot. You'll naturally lose more fluid and need to drink more to compensate for it.
  • If you're constipated. Increasing fluid intake adds moisture to the large intestine, which helps your body eliminate waste. And, if you take a laxative, you'll need to make up for fluids you lose.
  • If you're prone to urinary tract infections or kidney stones. Fluids may prevent infections and kidney stone formation.
  • If you're sick. High fever, vomiting and diarrhea can cause rapid dehydration, a condition that can be life threatening.

Dehydration Warning Signs

If you notice you're urinating less than usual or if you don't feel thirsty very often, check the color of your urine. It should be the color of straw if you're properly hydrated. If it’s much darker, it's a sign that you need more fluids.

Other warning signs include dry mouth, decreased salivation, dizziness, sunken eyes, rapid pulse and a loss of skin elasticity.

Source: Prepared by the Editors of The Johns Hopkins Medical Letter: Health After 50

Publication Review By: the Editorial Staff at

Published: 18 Jul 2013

Last Modified: 14 Aug 2014