Sodium Blood Test

What is a sodium blood test?

A sodium blood test measures the amount of sodium in your blood. Sodium is a type of electrolyte. Electrolytes are electrically charged minerals that help maintain fluid levels and the balance of chemicals in your body called acids and bases. Sodium also helps your nerves and muscles work properly.

You get most of the sodium you need in your diet. Once your body takes in enough sodium, the kidneys get rid of the rest in your urine. If your sodium blood levels are too high or too low, it may mean that you have a problem with your kidneys, dehydration, or another medical condition.

Other names: Na test

What is it used for?

A sodium blood test may be part of a test called an electrolyte panel. An electrolyte panel is a blood test that measures sodium, along with other electrolytes, including potassium, chloride, and bicarbonate.

Why do I need a sodium blood test?

Your health care provider may have ordered a sodium blood test as part of your regular checkup or if you have symptoms of too much sodium (hypernatremia) or too little sodium (hyponatremia) in your blood.

Symptoms of high sodium levels (hypernatremia) include:

  • Excess thirst
  • Infrequent urination
  • Vomiting
  • Diarrhea

Symptoms of low sodium levels (hyponatremia) include:

  • Weakness
  • Fatigue
  • Confusion
  • Muscle twitching

What happens during a sodium blood test?

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 will be collected into a test tube or vial. You may feel a little sting when the needle goes in or out. This usually takes less than five minutes.

Will I need to do anything to prepare for the test?

You don’t need any special preparations for a sodium blood test or an electrolyte panel. If your health care provider has ordered more tests on your blood sample, you may need to fast (not eat or drink) for several hours before the test. Your health care provider will let you know if there are any special instructions to follow.

Are there any risks to the test?

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.

What do the results mean?

If your results show higher than normal sodium levels, it may indicate:

  • Diarrhea
  • A disorder of the adrenal glands
  • A kidney disorder
  • Diabetes insipidus, a rare form of diabetes that happens when the kidneys pass an unusually high volume of urine.

If your results show lower than normal sodium levels, it may indicate:

  • Diarrhea
  • Vomiting
  • Kidney disease
  • Addison disease, a condition in which your body’s adrenal glands don’t produce enough of certain types of hormones
  • Cirrhosis, a condition that causes scarring of the liver and can damage liver function
  • Malnutrition
  • Heart failure

If your results are not in the normal range, it doesn’t necessarily mean that you have a medical condition needing treatment. Certain medicines can increase or decrease your sodium levels. If you have questions about your results, talk to your health care provider.

Is there anything else I should know about a sodium blood test?

Sodium levels are often measured with other electrolytes in another test called the anion gap. An anion gap test looks at the difference between negatively charged and positively charged electrolytes. The test checks for acid imbalances and other conditions.

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