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A sodium blood test is a routine test that allows your doctor to see how much sodium is in your blood. It’s also called a serum sodium test. Sodium is an essential mineral to your body. It’s also referred to as Na+.
Sodium is particularly important for nerve and muscle function. Your body keeps sodium in balance through a variety of mechanisms. Sodium gets into your blood through food and drink. It leaves the blood through urine, stool, and sweat. Having the right amount of sodium is important for your health. Too much sodium can raise your blood pressure.
A lack of sodium can cause symptoms such as:
The sodium blood test is often part of a basic metabolic panel. This is a group of related tests. The basic metabolic panel includes tests for:
Blood sodium can also be part of an electrolyte panel. Electrolytes are substances that carry an electrical charge. Potassium and chloride are other electrolytes.
This test may be ordered if you have:
You may also receive this test to monitor medications that affect your sodium levels. These include diuretics and certain hormones.
This test is performed on a blood sample, obtained by venipuncture. A technician will insert a small needle into a vein on your arm or hand. This will be used to fill a test tube with blood.
You don’t need to prepare for this test. Consume a normal amount of food and water before going to the testing site. You may have to stop taking certain medications before this test. But, drugs should only be stopped on a doctor’s instruction.
When the blood is collected, you may feel some moderate pain or a mild pinching sensation. Any discomfort should only last a short time. After the needle is taken out, you may feel a throbbing sensation. You’ll be instructed to apply pressure to the puncture. A bandage will be applied.
There are few risks to taking a blood sample. Rare problems include:
If you bleed for a long period after your test, it may indicate a more serious condition. Excessive bleeding should be reported to your doctor.
Your doctor will go over your results with you. Results range from normal to abnormal.
Normal results for this test are 135 to 145 mEq/L (milliequivalents per liter), according to the Mayo Clinic. But different laboratories use different values for "normal."
A blood sodium level lower than 135 mEq/L is called hyponatremia. Symptoms of hyponatremia include:
Hyponatremia can cause damage to cells. It makes them swell up with too much water. This may be particularly dangerous in areas such as the brain.
Hyponatremia is more often a problem in older adults. It can be caused by:
Hypernatremia means high levels of sodium in the blood. It’s defined as levels that exceed 145 mEq/L. Symptoms of hypernatremia include:
Hypernatremia is most often a problem in older adults, infants, and people who are bedridden. Causes of hypernatremia include:
Certain medications can also potentially cause hypernatremia. These include:
A blood sodium test is ordered by your doctor for a number of reasons. Sometimes it’s needed because you may be on certain medications that affect the sodium levels in your blood. Other times it may be part of a general health checkup. Either way it’s important to know how much sodium in your blood. Keeping it at the optimum level is good for your overall health.
Written by: Christine Case-Lo
Medically reviewed on: Sep 13, 2016: University of Illinois-Chicago, College of Medicine
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