The normal range for blood sodium levels is 135 to 145 milliequivalents per liter (mEq/L).

Normal value ranges may vary slightly among different laboratories. Talk to your doctor about the meaning of your specific test results.

Abnormal sodium levels can be due to many different conditions. To help determine the cause, your health care provider will consider the total amount of fluid in your body. This is done by looking at the turgor of your skin and swelling in the ankles, feet, and legs.

For greater-than-normal sodium levels (hypernatremia):

• If the amount of fluid in your body is low, you may have fluid loss due to excessive sweating, diarrhea, use of diuretics, or burns.
• If your total body water is normal, high sodium levels may be due diabetes insipidus (too little of the hormone vasopressin).
• If your total body water is high, this may indicate hyperaldosteronism, Cushing syndrome, or a diet that's too high in salt or sodium bicarbonate.

For lower-than-normal sodium levels (hyponatremia):

• Low total body water and sodium levels may be due to dehydration, vomiting, diarrhea, over diuresis, or ketonuria.
• Near-normal total body water may indicate SIADH, too much of the hormone vasopressin, hypothyroidism, or Addison's disease.
• An increase in total body water may indicate congestive heart failure, nephrotic syndrome or other kidney disease, or cirrhosis of the liver.

Additional conditions for which the test may be performed include:

• Acute adrenal crisis
• Diabetic hyperglycemic hyperosmolar coma
• Drug-induced hypothyroidism
• Hepatorenal syndrome
• Hypopituitarism