Sodium Blood Test
Reviewed
Also called: Na test, Sodium test, Serum sodium, Blood sodium
A sodium blood test measures the amount of sodium in your blood. Sodium is a type of electrolyte.
Specimen: Blood (from a vein in your arm)
Urgent safety information
Without treatment, extremely high levels of sodium may lead to a coma and become life-threatening. Without treatment, extremely low levels of sodium may also lead to a coma and become life-threatening.
Why this test may be ordered
- As part of a routine checkup
- To help find and monitor conditions that affect fluid, electrolyte, and acid-base balance
- If you have symptoms of high or low sodium levels
- If you take medicines that can affect your fluid balance
Preparation and collection
You may need to stop taking certain medicines before this test, so tell your provider about everything you take. But don't stop any medicines unless your provider tells you to. You may also need to fast (not eat or drink) for several hours before the test.
A health care professional will take a blood sample from a vein in your arm, using a small needle. This usually takes less than five minutes.
There is very little risk to having a blood test. You may have slight pain or bruising at the spot where the needle was put in, but most symptoms go away quickly.
Understanding results
Blood sodium levels that are too high or too low can be a sign of many different conditions.
- Higher than normal sodium level (hypernatremia): Sodium blood test results that are higher than normal may be a sign of a condition such as: dehydration, which may be caused by not drinking enough, diarrhea, or taking diuretic medicines (water pills), a disorder of the adrenal glands, a kidney disease. Limitation: 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. Next step: If you have questions about your results, talk with your provider.
What does low sodium (hyponatremia) mean?
Lower than normal sodium level (hyponatremia): Sodium blood test results that are lower than normal may be a sign of a condition, such as: a loss of sodium from diarrhea or vomiting, a condition that may cause the body to hold onto extra fluid (which dilutes sodium), including: kidney diseases, cirrhosis of the liver, heart failure. Limitation: If your results are not in the normal range, it doesn't always mean that you have a medical condition that needs treatment. Next step: 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.
- Results that are not in the normal range don't always mean a medical condition that needs treatment.
- Certain medicines, age, sex, and medical conditions can affect sodium levels.
- The test is often interpreted with other electrolyte tests.
- A single abnormal result may be due to temporary factors.
What to do next
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.
- What do my sodium test results mean in my specific situation?
- Do I need any follow-up tests?
- Should I change my diet or fluid intake based on these results?
- Are there any medicines I should avoid?
- What symptoms should I watch for that might indicate a worsening condition?
Evidence source
Source: U.S. National Library of Medicine (MedlinePlus). Practices and reference ranges may differ in your country.