Sodium (Na)

You get most of the sodium you need in your diet. If you take in too much, your kidneys get rid of the extra sodium in your urine (pee). Normally, your body keeps your sodium levels in a very narrow range. If your sodium blood levels are too high or too low, it may mean that you have a kidney problem, dehydration, or another type of medical condition.

Your health care provider may order a sodium blood test as part of your routine checkup or if you take medicines that can affect your fluid balance. You may also have this test if you have symptoms of too much or too little sodium in your blood. It can also help diagnose and manage conditions such as Addison disease, diabetes insipidus, syndrome of inappropriate antidiuretic hormone (SIADH), and other disorders that disturb your body's electrolyte balance.

Blood sodium levels that are too high or too low can be a sign of many different conditions. To make a diagnosis, your provider will usually look at the results of your sodium blood test with the results of other tests, such as measurements of other electrolytes.

A low sodium level (hyponatremia) can come from losing sodium (vomiting, diarrhea, sweating, certain water pills) or from holding on to too much water (heart failure, kidney disease, liver disease, or syndrome of inappropriate antidiuretic hormone). When sodium drops, water can move into brain cells and cause symptoms ranging from weakness and confusion to seizures or coma in severe cases. How quickly the level drops often matters more than the exact number.

A high sodium level (hypernatremia) is most often caused by not getting enough water (dehydration), large fluid losses (burns, fever, very high blood sugar, certain types of diabetes insipidus), or certain hormone problems. Symptoms range from thirst and irritability to confusion, seizures, and coma if levels rise sharply.

If your results are not in the normal range, it doesn't always mean that you have a medical condition that needs treatment. Certain medicines, your age, sex, and certain medical conditions can increase or decrease your sodium levels. If you have questions about your results, talk with your provider.