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 an electrolyte that helps control fluid balance, nerve function, and muscle function. Abnormal levels may indicate kidney problems, dehydration, or other conditions.
Specimen: Blood (from a vein in your arm)
Urgent safety information
Extremely high or low sodium levels can lead to coma and become life-threatening. Seek emergency care if you have severe symptoms such as confusion, seizures, or loss of consciousness.
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
Your provider will let you know how to prepare. You may need to stop taking certain medicines before this test. You may also need to fast (not eat or drink) for several hours before the test. Do not stop any medicines unless your provider tells you to.
A health care professional will take a blood sample from a vein in your arm using a small needle. After the needle is inserted, a small amount of blood is collected into a test tube or vial. The procedure 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
Your sodium blood test results will be reported as a number. Your provider will interpret your results based on your overall health, symptoms, and other test results. The following are general patterns.
- Normal sodium level: Your sodium level is within the normal range. This suggests your body's fluid and electrolyte balance is likely normal. Limitation: A normal result does not rule out all conditions. Some conditions may not affect sodium levels. Next step: Discuss any ongoing symptoms with your provider. No immediate action needed based on this result alone.
- Higher than normal sodium level (hypernatremia): May indicate dehydration, kidney disease, adrenal gland disorders, or diabetes insipidus. Limitation: This result alone is not diagnostic. Your provider will consider other tests and your clinical picture. Next step: Your provider will evaluate the cause and may order additional tests. Follow up as directed.
- Lower than normal sodium level (hyponatremia): May indicate loss of sodium from diarrhea/vomiting, conditions causing fluid retention (kidney disease, heart failure, cirrhosis), certain medicines, or Addison disease. Limitation: This result alone is not diagnostic. Many factors can affect sodium levels. Next step: Your provider will evaluate the cause and may order additional tests. Follow up as directed.
- 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
If your results are abnormal, your provider will likely repeat the test and/or order additional tests such as an electrolyte panel, basic metabolic panel, or comprehensive metabolic panel to help diagnose the cause. Treatment will depend on the underlying condition. Do not change your medicines without consulting your provider.
- 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?