Sodium (Blood)

Does this test have other names?

Na test

What is this test?

This test measures the levels of sodium in your blood. Sodium is a substance your body's cells need to work normally. Sodium helps make sure that your nerves and muscles can work as they should. Sodium is also important because it helps maintain the right balance of fluids in your body. The kidneys help keep sodium at a healthy level. You can get the sodium you need through your diet. But it's easy to take in too much sodium through your diet. When your body has too much sodium, your kidneys can't remove enough of it. Sodium collects in your bloodstream. This can lead to high blood pressure, which can cause other problems.

Too much sodium in the blood is called hypernatremia. Too little sodium in the blood is called hyponatremia. Hypernatremia can occur when you lose too many fluids. This can happen from sweating too much, vomiting, or diarrhea. Hyponatremia can occur when you drink large amounts of water or if you have problems with your kidneys that affect your ability to urinate.

Why do you need this test?

You may need this test if your health care provider thinks you have an imbalance of fluids and sodium. You may have symptoms such as:

• Problems with mental or cognitive function.

• Muscle cramps or twitching.

• Cravings for large amounts of salt.

• Confusion or forgetfulness.

• Problems with walking.

• General unwell feeling.

• Nausea.

• Tiredness (fatigue).

• Headaches.

• Shortness of breath.

• Fluid buildup or swelling in part of the body.

The test can check for:

• Diabetes that's not controlled well.

• Kidney problems, including advanced kidney failure.

Or you may need this test if you:

• Are taking certain medicines, such as water pills (diuretics).

• Are having sodium therapy.

• Lost a large amount of bodily fluids.

You may also have this test as part of a routine health check. 

What other tests might you have along with this test?

You may need other tests along with a sodium blood test. You may have tests to look at:

• Other electrolyte levels in your blood, such as potassium.

• Concentration of your urine.

• Level of sodium in your urine.

• Concentration of your blood.

• Levels of uric acid and urea.

• Acid-base balance in your blood.

What do your test results mean?

Test results may vary depending on your age, gender, health history, and other things. Your test results may be different depending on the lab used. They may not mean you have a problem. Ask your health care provider what your test results mean for you.

Normal sodium levels are usually between 136 and 145 millimoles per liter (mmol/L). Blood sodium levels below 136 mmol/L may mean you have low blood sodium (hyponatremia). Blood sodium levels greater than 145 mmol/L may mean you have blood sodium levels that are too high (hypernatremia). 

How is this test done?

The test is done with a blood sample. A needle is used to draw blood from a vein in your arm or hand. 

Does this test pose any risks?

Having a blood test with a needle carries some risks. These include bleeding, infection, bruising, and feeling lightheaded. When the needle pricks your arm or hand, you may feel a slight sting or pain. Afterward, the site may be sore.

What can affect your test results?

If your blood sample is collected incorrectly, your test results may be affected. Having high blood sugar (hyperglycemia) can also affect your test results.

Taking some medicines can also affect your test results. These include diuretics and nonsteroidal anti-inflammatory medicines, such as ibuprofen.

How do you get ready for this test?

Your health care provider will tell you what you need to do before this test. You may need to not eat or drink for several hours before the test. You may need to skip or delay certain medicines on the day of the test. Be sure your provider knows about all medicines, herbs, vitamins, and supplements you are taking. This includes medicines that don't need a prescription and any illegal drugs you may use.