Why Do You Retain Water After Exercise?

Water retention after exercise is a common issue, particularly among those who are beginning a new exercise program. There are all sorts of reasons your body could be holding extra water after you work out. Everything from the ambient weather to your nutrient levels to the amount of water you take in during exercise has an effect on the amount of water you retain after you exercise.

A woman is exercising outdoors. (Image: mihtiander/iStock/Getty Images)

Hot Weather

If you have been exercising in cooler weather and are now experiencing a weather change or have moved to a location with hotter weather, you may retain water after your workouts for the first few days. Lulu Weschler, a physical therapist and regular contributor to Ultracycling, says your blood plasma levels can increase up to 10 percent while your body is acclimating to exercising in hot weather. Because your blood plasma -- the fluid part of your blood that doesn't contain cells or platelets -- contains more water than any other substance, this increase in plasma levels can lead to a retention of water after your workouts for a few days.

Sodium Levels

Other than water, sodium is one of the most important substances in your blood while you exercise. This is because sodium plays an important role in the function of your muscles. While you exercise, you lose sodium in your sweat as well as in your urine, according to Weschler. If you consume enough water to increase your blood plasma volume but you don't increase your sodium levels, you can suffer from an ailment called hyponatremia. Hyponatremia can lead to fluid retention after exercise, so consume enough sodium while you exercise. The condition can also be quite dangerous, leading to pressure on your brain from excess blood volume in your brain capillaries, causing death if not treated quickly.


As odd as it may sound, fluid retention can be a result of dehydration. When your body is deprived of water, it begins to hoard it, so to speak. Similar to the way your metabolism slows down during starvation, when your body is starved of water, it begins to hold onto whatever fluid it receives. If you don't consume enough water during your workout, you may experience some temporary water retention while your body attempts to replenish its water stores.

Kidney Disease

Chronic dehydration can lead to kidney disease, according to MedlinePlus, a website published by the U.S. National Library of Medicine. When your blood plasma levels decrease as a result of dehydration, reduced blood flow to your kidneys can occur, which causes damage. One symptom of kidney disease is water retention due to an inability of your body to process water and expel it from your body. Watch for blood in your urine or extremely concentrated and dark urine for warning signs of kidney disease.


Although there are several causes of water retention, it's relatively easy to avoid the symptoms. Hydrate yourself adequately before and during exercise to avoid dehydration and subsequent water retention. Have the proper balance of sodium and water in your system while you work out. Monitor the weather and allow your body time to acclimate to changes in ambient temperatures, particularly temperature increases. Finally, although it's highly unlikely that you would cause yourself kidney failure, check with your doctor if you have eliminated all other causes for water retention. She may want to check you for kidney disease.

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