Definition

Every part of your body needs water to function. When you are healthy, your body is able to balance the amount of water that enters or leaves your body.

A fluid imbalance may occur when you lose more water or fluid than your body can take in. It can also occur when you take in more water or fluid than your body is able to get rid of.

Alternative Names

Water imbalance; Fluid imbalance - dehydration; Fluid buildup; Fluid overload; Volume overload; Loss of fluids; Edema - fluid imbalance; Hyponatremia - fluid imbalance; Hypernatremia - fluid imbalance; Hypokalemia - fluid imbalance; Hyperkalemia - fluid imbalance

Causes

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 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 and tissues).

Many medical problems can cause fluid imbalance:

• After surgery, the body often retains large amounts of fluid for several days, causing swelling of the body.
• In people with 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.
• When the kidneys do not work well because of long-term (chronic) kidney disease, the body cannot get rid of unneeded fluids.
• The body may lose too much fluid due to diarrhea, vomiting, severe 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, dehydration, and chemical imbalance of the blood.

Often, in people with fluid imbalance, a high or low blood level of sodium or potassium is present as well.

Medicines can also affect fluid balance. The most common are water pills (diuretics) to treat blood pressure, heart failure, liver disease, or kidney disease.

Treatment

Treatment depends on the specific condition that is causing the fluid imbalance.

When to Contact a Medical Professional

Contact your health care provider if you or your child has signs of dehydration or swelling, in order to prevent more serious complications.

References

Hall JE, Hall ME. Urine concentration and dilution: regulation of extracellular fluid osmolarity and sodium concentration. In: Hall JE, Hall ME, eds. Guyton and Hall Textbook of Medical Physiology. 14th ed. Philadelphia, PA: Elsevier; 2021:chap 29.

Kashkouli A, Berl T, Sands JM. Disorders of water metabolism. In: Johnson RJ, Floege J, Tonelli M, eds. Comprehensive Clinical Nephrology. 7th ed. Philadelphia, PA: Elsevier; 2024:chap 9.