Sodium Blood Test

A sodium blood test measures the amount of sodium in your blood. Sodium is a type of electrolyte. Electrolytes are minerals that have an electrical charge when they are dissolved in water or body fluids.

You have electrolytes in your blood, urine (pee), tissues, and other body fluids. They help control the amount of fluid and the balance of acids and bases (pH balance) in your body. Sodium also helps your nerves and muscles work properly.

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.

Why this test is done

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.

Symptoms of high sodium levels (hypernatremia) include:

• Thirst
• Urinating (peeing) very little
• Vomiting
• Diarrhea
• Confusion
• Muscle twitching
• Seizures

Without treatment, extremely high levels of sodium may lead to a coma and become life-threatening.

Symptoms of low sodium levels (hyponatremia) include:

• Weakness
• Fatigue
• Confusion
• Muscle twitching
• Seizures

Without treatment, extremely low levels of sodium may also lead to a coma and become life-threatening.

How to prepare

Your provider will let you know how to prepare for a sodium blood test. 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. Ask your provider if you have any questions.

Sample type

Blood

Other names for this test

Na test