Sodium (Na)

This is a test used to check whether your sodium concentration is within normal limits. It helps check electrolyte balance and kidney function. It also helps to monitor long-standing or sudden onset of high sodium levels (hypernatremia) or low sodium levels (hyponatremia). The test may be done if you have dehydration, edema, problems with blood pressure, or nonspecific symptoms. It may be done as part of a routine lab evaluation. It may also be done to monitor certain chronic conditions, such as high or low blood pressure.

This test measures the level of sodium in the blood. Sodium is a mineral that is vital to normal body function. It is an electrolyte. This is a positively charged molecule. It works with other electrolytes, such as potassium, chloride, and total carbon dioxide (CO2), to help regulate the amount of fluid in the body. Sodium is present in all body fluids. However, it is found in the highest concentration in the blood and in the fluid outside the body's cells. We get sodium in our diet from table salt (sodium chloride or NaCl) and from most of the foods we eat. Most people have an adequate intake of sodium. The body uses what it needs and the kidneys excrete the rest in the urine. The body maintains sodium concentration within a very narrow range. It does this by producing hormones that can increase (natriuretic peptides) or decrease (aldosterone) sodium losses in urine. The body produces a hormone that prevents water losses (antidiuretic hormone [ADH]) and controls thirst. Even a 1% increase in blood sodium will make you thirsty. This causes you to drink water. This returns your sodium level to normal.

Abnormal blood sodium is usually due to a problem with one of these systems. When the level of sodium in the blood changes, the water content in your body also changes. These changes can be associated with dehydration or excess fluid (edema), especially in the legs.


A blood sample is obtained by inserting a needle into a vein in the arm.


  • Adults: 136 to 145 mEq/L (136 to 145 mmol/L)

  • Adults older than 90 years: 132 to 146 mEq/L (132 to 146 mmol/L)

  • Premature infants, cord blood: 116 to 140 mEq/L (116 to 140 mmol/L)

  • Premature infants at 48 hours: 128 to 148 mEq/L (128 to 148 mmol/L)

  • Full term neonates, cord blood: 126 to 166 mEq/L (126 to 166 mmol/L)

  • Full term neonates: 133 to 146 mEq/L (133 to 146 mmol/L)

  • Children: 138 to 146 mEq/L (138 to 146 mmol/L)

Ranges for normal findings may vary among different laboratories and hospitals. You should always check with your caregiver after having lab work or other tests done to discuss the meaning of your test results and whether your values are considered within normal limits.


Your caregiver will go over the test results with you. Your caregiver will discuss the importance and meaning of your results. He or she will also discuss treatment options and additional tests, if needed.


It is your responsibility to obtain your test results. Ask the lab or department performing the test when and how you will get your results.