Dehydration may be prevented by maintaining adequate water balance in the body. This involves drinking regularly, before thirst develops. People can often carry a bottle of water with them throughout the day for easy access to fluids. A general rule of thumb for determining baseline daily fluid needs is to multiply the person's body weight in kilograms by 30 milliliters (ml). 

Prevention also depends on becoming aware of circumstances that put people at greater risk of dehydration. When such circumstances are foreseen, prehydration can be helpful. Prehydration means taking in additional fluids prior to anticipated fluid loss. For instance, breastfeeding mothers often drink additional fluids before a scheduled feeding. Or, people can drink several glasses of water prior to gardening on a hot day.

Additional dehydration prevention methods include:

• Drink cool or cold liquids (e.g., water, sports drinks) before, during and after play, sports or any type of physical exertion. Cold fluids are more efficiently absorbed than warm fluids. They also play a part in cooling body temperature, helping to avoid complications such as heat exhaustion and heat stroke. Drinking should occur every 20 minutes during exercise. The amount consumed may depend on a person’s size, for example:

Body Weight	Amount of Fluid Intake (every 20 minutes)
Less than 88 pounds (40 kilograms)	5 ounces (148 milliliters)
88 to 132 pounds (40 to 60 kilograms)	9 ounces (266 milliliters)
More than 132 pounds (60 kilograms)	10 to 12 ounces (296 to 355 milliliters)

• Take steps to prevent overheating. This may include taking breaks every 20 to 30 minutes during sports or other vigorous activity, as well as periodically stepping out of the heat or humidity into a shaded or cool location. Outdoor sports should be performed in early mornings or late afternoons to avoid physical exertion during the hottest times of the day.
  
  
• Limit intake of sodium, caffeine and alcohol. Foods and beverages containing high amounts of salt can draw water out of body cells to dilute high levels of salt in the mouth and gastrointestinal tract. The more sodium that is ingested, the higher the risk of mild dehydration. Caffeine has a diuretic effect, increasing urination above normal levels and contributing to the loss of excess fluids from the body. Alcohol interferes with the body’s ability to absorb water through the gastrointestinal tract.
  
  
• Know what to do in extreme survival conditions. People who participate in hiking or other outdoor activities (e.g., mountain climbing, rock climbing) should be prepared with additional stores of fluids in case they get lost or are stranded. It is important to remain as hydrated as possible until help arrives.

Because certain medications may increase the risk of dehydration (e.g., diuretics, chemotherapy), patients should consult their physician about the best way to prevent dehydration. A physician may encourage drinking extra water with the medication, or prescribe antiemetics (anti-nausea medications) to reduce the likelihood of fluid loss from vomiting.

People with a high risk of dehydration (e.g., infants, children, the elderly) may need extra hydration prior to a medical procedure requiring that foods and liquids be restricted. Anyone concerned about loss of fluids prior to such a procedure should consult their physician. The use of intravenous (I.V.) fluids may be recommended before, during and after the procedure to ensure adequate hydration.

Salt pills are not advised as they can cause hypernatremia (dehydration caused by excess sodium in the body). In the past, salt pills were recommended for use during sports activities in hot weather to help prevent dehydration. However, they are not used much today.