Adults: 135 - 145 mEq/L (135 – 145 mmol/L)
Children: 138 - 145 mEq/L (138 – 145 mmol/L)
In the International System of Units (SI), sodium in the blood is measured in mmol/L. The valence of sodium is +1 so the numeric values are the same in mmol/L or in mEq/L.
Each laboratory must establish its own normal ranges for sodium in the blood. These ranges depend on the makeup of the local population, the technologies used and the accuracy of the measurement. There may be also slight differences in the normal levels according to age, gender, race or ethnic origin, geographic region, diet, type of sample and other relevant status.
Your doctor will study the results along with your medical record, screenings, physical condition, symptoms and any other relevant information about your situation.
Sodium is an electrolyte found mainly in the extracellular fluid. Sodium plays an important role in maintaining a correct osmolality. Osmolality measures the electrolyte-water balance of the body. Plasma osmolality measures primarily the amount of dissolved sodium in the serum (blood).
Sodium is the main electrolyte in the bodily fluids (urine, blood, stools) and its role along with potassium, chloride and CO2 (bicarbonate) is essential to maintain electrical neutrality in the cells and the acid-base balance.
Up to 90% of the human body is water. Water can be found inside the cells (two-thirds) or outside the cells (one-third). Sodium, potassium, proteins and other soluble substances are dissolved in it. The total concentration of these substances (osmolality) inside and outside the cells must be the same. That way, if there is an increase in the solutes (dissolved particles) outside the cells that pulls the water out of the cells and vice versa. Thus, sodium is a key substance to regulate osmolality.
Sodium is supplied in the food we eat. Sodium is found in salt (sodium chloride). Sodium is excreted primarily in urine by the kidneys. A little part can be excreted also through stools or sweat.
Sodium balance works as follows:
Three major hormones are involved in regulating sodium and water balance in the body:
A sodium blood test can be useful to determine your kidney function. It is usually performed along with the study of sodium in urine to get more information.
It helps also to evaluate the hormones involved in the sodium balance and estimate the hydration state of the body.
Abnormally low levels of sodium in the blood (hyponatremia) may be due to:
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The following values are considered to be normal values:
IMPORTANT: These levels are expressed in mEq/L (mmol/L). They are an example of a healthy man of about 45 years of age with no known disease, not taking any medication and with an appropriate intake of sodium in the diet. The ranges can be different depending on the laboratory or on your personal circumstances.