Hyponatremia is a condition where blood levels of sodium dip too low, and it can be dangerous. It may surprise you to know that developing it has nothing to do with the sodium that you eat.
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Sodium often has a bad reputation—when you consume too much of it in your diet, that is. Truth is, sodium is an electrolyte that plays incredibly important roles in the body, such as supporting fluid balance, nerve impulses and muscle contraction. Your doctor may recommend that you limit your sodium intake, as too much is linked to high blood pressure, heart disease and stroke. The flip side? Having sodium levels that are too low can potentially cause some harm to your health as well.

There are many causes of low blood sodium levels, a condition called hyponatremia. Surprisingly, the causes have nothing to do with the sodium you get from your diet. If you want to learn more about hyponatremia, what causes it and what it means, read on to learn all about this common condition.

What Is Hyponatremia?

Sodium is an important mineral that our body needs to maintain at a certain level to function properly—typically between 135 and 145 milliequivalents/liter.

Hyponatremia is a condition that affects about 2% of adults in the U.S. every year, past research indicates. A diagnosis of hyponatremia means that your sodium blood level has fallen below 135 mEq/L, according to the National Kidney Foundation.

Symptoms of hyponatremia include confusion, lethargy, nausea and vomiting. One sign of hyponatremia is water retention. When sodium levels are too low, extra fluid can enter the cells in the body, making them swell. Typically, as sodium levels normalize, this effect subsides.

Extreme cases of hyponatremia can lead to seizure, coma and even death.

What Causes Hyponatremia?

Having low sodium blood levels can negatively impact your health. Intuitively, it makes sense to think that the best way to prevent this condition would be to eat more salt, but oftentimes, diet has nothing to do with developing hyponatremia.

Rather, there are specific health conditions that increase the risk of developing hyponatremia.

Kidney failure

One of the many important things your kidneys do is remove excess fluid from your body. If your kidneys aren't working, your body may hang onto too much fluid, which can dilute sodium levels in the blood.

Congestive heart failure

Congestive heart failure is when a person's heart is not pumping blood as well as it should. In the later stages of the condition, your body has trouble excreting water through urine, allowing fluid to accumulate in your body. Additionally, medications that treat congestive heart failure may also cause hyponatremia as a side effect.

Liver disease

Electrolyte imbalances are common in patients with end-stage liver disease. As such, hyponatremia can occur.

Diarrhea or vomiting

When you vomit or have diarrhea, your body loses fluid and electrolytes, including sodium.


Sometimes, the medication you take can trigger another issue altogether. Certain diuretics, antidepressants and antiepileptics have all been linked to hyponatremia. In some cases, antihypertensive agents, antibiotics and proton pump inhibitors can also cause low levels of sodium in the blood.

Underactive thyroid (hypothyroidism)

Having an underactive thyroid affects certain hormones that play a role in water balance in the body. This can result in more dilute blood levels and hyponatremia.

Drinking too much water

Consuming excessive amounts of water, especially if you do so when sweating a lot (e.g., during a long endurance activity) can also dilute your body's sodium levels and lead to hyponatremia.

How do you treat hyponatremia?

If you have a diagnosis of hyponatremia, it is best to manage this condition with your health care provider. Some cases are treated by limiting fluid intake, while others may resolve with the help of certain medications. In certain cases, IV fluids may be needed.

Bottom Line

Hyponatremia is a condition defined as having a lower-than-ideal blood sodium level, which can be dangerous. Hyponatremia is not caused by eating a low-sodium diet, but is often the result of certain health conditions. Treatment options include limiting fluid intake, medications or IV fluids.