A fluid imbalance refers to an abnormal level of fluids in the body.
Your body is constantly losing water through breathing, sweating, and urinating. If you do not take in enough fluids or water, you become dehydrated.
Your body may also have a hard time excreting (getting rid of) fluids. As a result, excess fluid builds up in the body. This is called fluid overload (volume overload). This can lead to edema (excess fluid in the skin).
Many medical problems can cause fluid imbalance:
It is common to retain large amounts of fluid for several days after surgery (causing swelling of the body).
In heart failure, fluid collects in the lungs, liver, blood vessels, and body tissues because the heart does a poor job of pumping it to the kidneys, where it can be eliminated.
When the kidneys do not work well because of chronic kidney disease, the body cannot get rid of unneeded fluids.
The body may lose too much fluid due to diarrhea, vomiting, excessive blood loss, or high fever.
Lack of a hormone called antidiuretic hormone (ADH) can cause the kidneys to get rid of too much fluid. This results in extreme thirst and dehydration.
A fluid imbalance is often associated with imbalances of sodium (hyponatremia, hypernatremia), potassium (hypokalemia, hyperkalemia), and other chemicals that help regulate body fluids.
Medicines can also affect fluid balance. The most common are water pills (diuretics) to treat blood pressure.
Treatment depends on the specific condition that is causing the fluid imbalance.
When to Contact a Medical Professional
Call your health care provider if you or your child have signs of dehydration or swelling, in order to prevent more serious complications.
Skorecki K, Ausiello D. Disorders of sodium and water homeostasis. In: Goldman L, Schafer AI, eds. Goldman's Cecil Medicine. 24th ed. Philadelphia, Pa: Elsevier Saunders; 2011:chap 118.
Verbalis JG. Disorders of water balance. In: Taal MW, Chertow GM, Marsden PA, et al., eds. Brenner and Rector's The Kidney. 9th ed. Philadelphia, Pa: Elsevier Saunders; 2011:chap 15.
Brent Wisse, MD, Associate Professor of Medicine, Division of Metabolism, Endocrinology & Nutrition, University of Washington School of Medicine. Also reviewed by David Zieve, MD, MHA, Bethanne Black, and the A.D.A.M. Editorial team.