A sodium test measures the amount of sodium present in the blood. Sodium is both an electrolyte and mineral. It helps to keep the water and electrolyte balance in the body. Sodium is also important in how nerves and muscles work. This test can be used to check on the progress of diseases associated with the kidneys or adrenal glands.
If the sodium levels in the body are too high (hypernatremia) or too low (hyponatremia), it means that you may have a kidney problem, dehydration, or other medical conditions.