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.