Hyponatremia happens when sodium levels in the blood dip below a certain level, often triggered by overhydrating. Normal plasma contains between 136 and 145 milliequivalents per liter (mEq/L) of sodium; hyponatremia can set in when that level dips below 135 mEq/L. Notice how fine the line is between balance and distress.
There are three ways sodium fluctuations can happen in the body:
- Hypovolemic hyponatremia occurs when both sodium and water levels are lower than normal. This is the most common form and, as we've mentioned, can be the result of overconsuming fluids or failing to replenish electrolytes after extended periods of exercise.
- Hypervolemic hyponatremia happens when the sodium imbalance is the result of excess water. But it can also be caused by kidney, heart or liver failure, affecting organs that play vital roles in the exchange of fluids in the body.
- Euvolemic hyponatremia describes normal fluid levels but abnormally low sodium counts. This is usually complicated by chronic health conditions, including cancer. It can also be triggered by certain medications, particularly diuretics or pain relievers that may cause abnormal perspiration or urination. The unusually high output of fluids can quickly create sodium imbalance.
The importance of sodium in the human body is critical. Sodium is how we maintain blood pressure and regulate our fluids. It also provides support for muscle tissue. Maintaining a proper balance is critical to a host of bodily operations, including renal and brain function [source: Schirber].
Other factors can also cause the onset of hyponatremia, including recreational drug use or heavy drinking, low-sodium and water-intensive diets, and conditions such as primary polydipsia, which interferes with your ability to regulate thirst and, as a result, makes you drink too much water [source: Mayo Clinic].