Non-small cell lung cancer (NSCLC) causes cancerous cells to grow within lung tissues. Some people with NSCLC may experience low sodium levels, known as hyponatremia. Symptoms may include fever, headaches, and nausea.

NSCLC is a common form of cancer and cause of death in the United States. The disease can also cause other conditions, including hyponatremia.

People with hyponatremia have abnormally low sodium levels, which causes water to move into cells around the body. This water causes swelling, which can lead to symptoms that include confusion, seizures, and nausea.

Keep reading to learn more about hyponatremia and its relationship with NSCLC.

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Electrolytes are minerals in the body that contain an electric charge. They perform various functions around the body, including balancing water levels and moving nutrients into cells. People with electrolyte disorders have electrolyte levels that are too high or too low, which can cause a range of symptoms.

Hyponatremia is the most common electrolyte disorder in people with lung cancer. It causes low sodium levels and swelling around the body.

According to the National Kidney Foundation, normal sodium levels are between 135–145 milliequivalents per liter. People have hyponatremia when their sodium levels fall below this normal range.

Electrolyte imbalances are common in people with cancer and can interfere with treatment. A 2017 study estimates that around 20–44% of people with lung cancer may have hyponatremia. People with NSCLC could have hyponatremia due to the side effects of medication or chemotherapy.

The study notes that almost 20% of people with NSCLC develop hyponatremia as their disease progresses.

When sodium levels are just below normal, the condition is usually manageable and not life threatening.

However, even mild cases of hyponatremia can cause:

  • longer hospital stays
  • delays to chemotherapy
  • lower quality of life
  • interference with an individual’s response to treatment

People with severe hyponatremia have a greater risk of dying in the hospital. However, treatment to restore sodium levels could help people with NSCLC to live longer.

The symptoms of hyponatremia in people with NSCLC will vary depending on how low sodium levels are and how quickly they fell. People with acute hyponatremia that develops in fewer than 48 hours may experience:

  • headaches
  • nausea
  • vomiting
  • muscle cramps
  • slow heartbeat
  • high blood pressure
  • inability to regulate body temperature
  • brain swelling
  • convulsions
  • coma

In chronic hyponatremia cases that occur over more than 48 hours, symptoms can also include:

  • weakness
  • loss of appetite
  • nausea
  • vomiting

Even mild to moderate hyponatremia can cause long-term complications, such as:

  • difficulty concentrating or walking
  • increased rate of bone loss
  • greater risk of falls and broken bones

However, some people with mild hyponatremia will experience no symptoms at all.

People with NSCLC may experience no symptoms in the early stages of hyponatremia, making some cases difficult to detect early.

Doctors can identify the condition from routine laboratory tests that people with NSCLC may undergo, such as blood tests. They will use these tests to check for signs of hyponatremia, including:

  • electrolyte and water balances
  • concentrations of particles in the urine
  • blood fluid volume
  • kidney, thyroid, and adrenal function

Doctors may also ask the person about symptoms that could indicate hyponatremia, such as confusion or seizures.

Treatment for people with NSCLC and hyponatremia will depend on the specifics of their condition, such as the duration and extent of low sodium levels. A common approach to treatment involves limiting fluid intake to reduce swelling.

Doctors may prescribe a vasopressin receptor antagonist. Vasopressin is a hormone that tightens blood vessels and increases water reabsorption in the kidneys. These medicines help the kidneys to remove large amounts of urine to reduce excess water without reducing sodium.

Other treatment options include:

  • hypertonic saline
  • isotonic saline
  • loop diuretics
  • urea

Saline solutions can increase sodium levels, including hypertonic and isotonic saline. People who require these saline solutions must gradually receive treatment to prevent damaging the nervous system, which may have adapted to a low-sodium environment.

Preventing electrolyte changes can protect people with NSCLC from the adverse effects of low sodium. However, many factors can combine to cause hyponatremia, making it difficult to prevent.

Longstanding and new cancer therapies can cause hyponatremia in people with NSCLC. Clinicians will closely monitor electrolyte levels in people receiving chemotherapy, targeted therapy, and checkpoint inhibitors. They can then act right away to prevent sodium levels from dropping too low and causing problems.

A 2019 study suggests that lowering fluid intake before starting chemotherapy could reduce the risk of hyponatremia.

NSCLC is a common form of cancer in the U.S. Some people with NSCLC will develop hyponatremia, where their sodium levels fall below the normal range. Hyponatremia causes swelling around the body and various symptoms, including headaches, nausea, and vomiting.

People with severe hyponatremia are at an increased risk of dying in the hospital. Hyponatremia is treatable with simple approaches, such as restricting fluid intake. Doctors may prescribe medications or saline solutions to remove water or increase sodium levels.