Basic Metabolic Panel – Sodium

Part 1 of a closer look at the Basic Metabolic Panel or BMP that most people have run every time they go to the doctor. Today’s focus is sodium.


The normal range is 135-145 mEq/L or that is the normal range for 95% of the population, so you may fall outside of that range and be totally normal. If you are below that level, we call it hyponatremia, and if you are above that level, we call it hypernatremia. These word come from hypo (meaning under) or hyper (meaning over), natrium (meaning sodium), and emia (meaning a condition of the blood).

What Are They Looking For:

Hyponatremia especially below 125 mEq/L is the most worrying and tends to result in nausea, vomiting, headache, confusion, and even seizures and coma. But if you are a little under the normal range then you might just have some general discomfort.

Hypernatremia is most concerning above 157 mEq/L but the symptoms are a little more vague, such as lethargy, weakness, and irritability though it can also result in seizures and coma.

Hyponatremia is the one most likely to present itself in a severe state as the thirst response normally kicks in to prevent us from becoming hypernatremic.

Organs Involved:

For such a small molecule, sodium involves a large number of organs. The heart, kidney, liver, vessels, thyroid, and adrenal gland are some examples. All of these systems work in conjunction to keep everything in balance, so when things go awry it can be a little more concerning. These changes normally result from chronic medical conditions that have their own symptoms associated with them though knowing the sodium level can help narrow the differential diagnosis.


All of the treatments looks to correct the salt/water balance and then treat the underlying condition. Normally saline, which is just water and table salt at physiologic concentrations, or some derivative is given in the setting of hyponatremia. With hypernatremia, a more dilute form is need as it is primarily fluid that is lacking.

While hyponatremia can result from various medical conditions, such as liver cirrhosis, hypothyroidism, and Addison’s disease, a more likely cause is vomiting or diarrhea.

Hypernatremia on the other hand can result from diabetes insipidus and Conn’s Syndrome, but is more likely to be the result of excess sweating and poor water intake.

Take Home Point:

If your sodium levels are a little outside of the normal range and you feel fine, your doctor is unlikely to pursue that further. Do not be concerned about that because often small fluctuations occur due to food and water intake.