Hydration basics

Every body needs enough water. Inadequate fluid intake can lead to dehydration that affects your mental and physical performance. The first step to being well hydrated is to drink fluids and eat foods high in water content throughout the day. Try to drink half your body weight in fluid ounces per day. For example, if you weigh 150 lb, then you need about 75 fl oz daily. Here are a few more tips to maintaining hydration throughout the day.

Hydration during exercise

Many factors affect hydration needs, including how much you sweat, the type and duration of exercise, the environment, and type of equipment worn. Don’t rely on thirst as a good indicator of your fluid needs; consume recommended amounts regularly throughout your activity. Below are some general guidelines.

For exercise lasting up to one hour: Drink water—about 3–8 oz every 15–20 minutes. (A gulp is about 1–2 oz.)

For exercise lasting longer than one hour: Drink 3–8 oz water + carbs + electrolytes—basically, a good sports drink—every 15–20 minutes.

A sports drink should contain (per 8 oz):

  • Carbohydrates 12–24 g
  • Sodium 82–163 mg
  • Potassium 18–46 mg

In general, limit your fluid intake during exercise to about one quart per hour, or as much as 1.5 qt/hr in hot weather. However, when you’re active in extreme environments such as heat, humidity, cold, or altitude, your fluid needs might be much higher. But in any environment, don’t exceed 1.5 qt/hr, or 12 quarts per day, during work in the heat. Learn more on HPRC’s webpage on staying hydrated during exercise.

Hydration after exercise

Dehydration greater than 2% of body weight can impair heat regulation and mental and physical performance. Review your hydration status by checking your weight before and after exercise whenever possible. More than a 2% weight loss indicates dehydration. (For example, 2% weight loss in a 150 lb warrior is 3 lbs.) You also can use the urine color chart below to estimate how hydrated you are.

Are you hydrated? Take the urine color test: Hydrated shows color from Optimal as very pale yellow to Well Hydrated as medium yellow. Dehydrated shows dark yellow colors. You need to drink more water. Brown color: Seek medical aid. May indicate blood in urine or kidney disease. This color chart is not for clinical use. Some vitamins and supplements might cause a darkening of the urine unrelated to dehydration. Adapted from USAPHC by the Human Performance Research Center. hprc-online.org

Rehydrate with fluids and foods. For every pound of body weight lost, consume 16–24 oz by drinking fluids and eating high-water-content foods throughout the day. These include:

  • Fluids—water, sports drinks, 100% fruit juice (diluted), milk, and milk alternatives (soy, almond)
  • Foods— fruit (watermelon, grapes, peaches, etc.), high-water-content vegetables (zucchini, celery, cucumbers, tomatoes), soup, yogurt, and sherbet/sorbet

Replenish sodium by consuming beverages or foods that contain sodium (salt). Drinking too much plain water and/or not consuming enough sodium can result in hyponatremia (low sodium levels in your blood), which can be very serious if not treated. Be aware of the signs and symptoms: headache, vomiting, swollen hands and feet, confusion, and wheezy breathing.

You might find it challenging to drink enough fluids, but some simple reminders can help. First, keep a bottle on hand. Just seeing the water bottle is a great reminder to drink more. Also, always drink water with meals and snacks. Sick of plain water? Add sliced lemon, lime, mint, cucumber, or fruit to your water. Or add to a water pitcher and keep in your refrigerator.

Resources

Sawka, M.N., Burke, L.M., Eichner, E.R., Maughan, R.J., Montain, S.J., & Stachenfeld, N.S. (2007). Exercise and fluid replacement (American College of Sports Medicine position stand). Medicine & Science in Sports & Exercise, 39(2), 377–390. doi:10.1249/mss.0b013e31802ca597

Baker, L. B., & Jeukendrup, A. E. (2014). Optimal composition of fluid-replacement beverages. Compr Physiol, 4(2), 575-620. doi: 10.1002/cphy.c130014

Institute of Medicine. Dietary Reference Intakes for Water, Potassium, Sodium, Chloride, and Sulfate. Washington, DC: The National Academies Press; 2005. DOI: https://doi.org/10.17226/10925