What to Know About Hyponatremia (Low Sodium) (2024)

Hyponatremia means the concentration of sodium in your blood is lower than what is needed for key functions like normal blood pressure, muscle contractions, and nerve signals in your body. Recovery time from low sodium levels will vary with the cause, symptoms, and severity, but healthcare providers target the first six hours for treatment.

If hyponatremia is acute, it can have a sudden onset caused by excessive sweat or drinking too much water. If it lasts more than 48 hours, it is considered chronic and more likely to have a cause like head injury or a medical condition. Some cases can be severe and take longer to resolve.

This article takes a closer look at the symptoms and causes of hyponatremia and explains how the condition is diagnosed and treated.

Symptoms of Low Sodium Levels

While people with mild hyponatremia often have no symptoms, the likelihood of them occurring increases the more that sodium levels drop.

Common signs and symptoms of low sodium include:

• Headaches, dizziness, and/or loss of balance
  
• Fatigue, drowsiness, mental confusion, or trouble concentrating
• Loss of appetite, nausea, or vomiting
• Reduced urine output (pee)
• Profuse or sudden sweating
• Muscle cramps, weakness, or spasms
• Irritability, restlessness, or other mood and personality changes
  
• Seizures and/or loss of consciousness
  

What Causes Hyponatremia?

Sodium is an essential mineral and most people in the United States have too much of it in their diet, making acute or chronic hyponatremia uncommon. Hyponatremia can occur due to diet and lifestyle factors or medical conditions that affect the balance of water and sodium in the body.

Types of Hyponatremia

There are three main types of hyponatremia, reflecting the different ways that your body can have too little sodium, too much water, or both that lead to dilutional hyponatremia. They describe fluid status and are called:

• Euvolemic hyponatremia (relatively normal fluid), but with changes due to exercise, hormones, health conditions, or medication. The most common type is related to what's called syndrome of inappropriate antidiuretic hormone (SIADH) secretion.
• Hypervolemic hyponatremia, with high fluid levels often seen with chronic kidney disease, heart failure, and other significant health conditions
• Hyposmolar hyponatremia, also called hypotonic hyponatremia. Contributing factors include water intake as well as the body's ability to form and excrete urine and its components.

Lifestyle Factors

Excessive sweating can cause the rapid loss of sodium. Humidity and environmental factors can contribute to the risk. Sweat and other body fluids are high in sodium. If you are unable to properly replenish sodium supplies after heavy sweating, sodium levels can drop precipitously.

If you drink excessive amounts of water after sweating without replacing electrolytes (essential minerals like sodium, calcium, and potassium), sodium levels are diluted and can drop even further. Overhydration further increases the risk. You also may need to consume more salt.

Medical Causes

There are medical conditions that can cause hyponatremia. Some develop slowly over time with symptoms developing gradually. Others develop rapidly with symptoms developing abruptly.

Medical causes of hyponatremia include:

• Adrenal insufficiency: The adrenal glands produce a hormone called aldosterone which balances sodium and potassium levels in the body. Adrenal insufficiency, also known as Addison's disease, disrupts this balance.
• Cerebral salt wasting syndrome(CSWS): This rare condition in which a brain injury alters the function of the kidneys, causing them to clear excessive amounts of sodium from the body.
• Cirrhosis: This is the scarring of the liver, the condition of which can cause fluid retention. The level of retention increases in tandem with the severity of the liver damage.
• Congestive heart failure: This is the inability of the heart to efficiently pump blood through the body, causing fluid build-up and the onset of hyponatremia.
• Diarrhea: Severe diarrhea can lead to a condition called hypovolemia in which the extreme loss of fluid can cause hyponatremia.
• Diuretics: Also known as "water pills," these drugs treat high blood pressure by increasing the passing of urine. This can deplete excess amounts of sodium from the body.
• Ecstasy: This is a recreational amphetamine drug that has been linked to severe and sometimes fatal cases of hyponatremia.
• Syndrome of inappropriate anti-diuretic hormone (SIADH): This is an uncommon disorder that causes the overproduction of anti-diuretic hormone (ADH), causing your body to retain water instead of excreting it in urine.

Diagnosis

Hyponatremia is diagnosed with a physical exam, lab tests, and a review of your medical history. Central to the diagnosis is a blood test that measures the concentration of sodium in your blood.

The levels are measured in milliequivalents per liter (mEq/L) and classified as follow:

• Normal: 135 to 145 mEq/L
• Hyponatremia: Under 135 mEq/L
• Severe hyponatremia: Under 120 mEq/L

The physical exam and medical history provide clues as to the underlying cause. Tests will check for abnormalities in your blood pressure, urine volume, and urine concentration. Other blood tests may look for abnormalities in your adrenal hormone levels or liver function.

Your healthcare provider will also check for neurological (nervous system-related) problems such as a loss of alertness, concentration, or orientation.

Recovering from Low Sodium Levels

The treatment of hyponatremia can be simple at times and challenging at others. Generally, the focus is on managing the underlying cause while slowly restoring sodium and fluid balance in the first six hours of treatment, though it may take days or longer in chronic, complicated cases.

Dietary Intake

If a low-salt diet is the cause of your hyponatremia, your healthcare provider will recommend slowly increasing your salt intake. The recommended sodium intake is around 1 teaspoon of salt per day for adults and 1/2 teaspoon of salt per day for children.

You will also be advised to drink enough water—around 12 cups per day for females and 16 cups per day for males—but not to overhydrate.

Your healthcare provider can discuss dietary changes that are meant to prevent future episodes of hyponatremia. Keep in mind that the salt in processed foods, bread, pasta, sauces, and even desserts counts toward the daily recommended intake.

Intravenous Sodium Replacement

If you have severe hyponatremia, you may need sodium to be replaced with intravenous (IV) fluids. This is when fluids containing water, sodium, and other key electrolytes are delivered gradually by "drips" into a vein using a needle.

The medical team will restore the sodium level over the course of several hours or days, depending on the severity of your condition. They then can move forward in addressing and treating any underlying cause to ensure your best chances of recovery.

Medications

There are few medications that are consistently effective in treating hyponatremia.

Drugs called vasopressin receptor antagonistsare sometimes used in people who have fluid retention and avoided in those with low fluid volumes. These drugs work best in people with congestive heart failure, cirrhosis, and SIADH.

Declomycin (demeclocycline) is an antibiotic sometimes used to treat SIADH. The results can vary, with some people experiencing an overcorrection of sodium levels. The drug can also cause kidney problems and photosensitivity (sensitivity to the sun) in some.

Complications of Low Sodium Levels

The complications of hyponatremia can vary depending on the severity of symptoms and what caused them. Keep in mind that hyponatremia occurs for very different reasons, whether a loss of volume caused by dehydration in runners or electrolyte changes with chronic kidney disease.

Complications of Acute Hyponatremia

With acute hyponatremia, the rapid decline in blood sodium can lead to serious and sometimes irreversible health complications. Due to the rapid increase of fluids in the brain and other organs, a person with acute hyponatremia may experience:

• Cerebral edema: This is the swelling of the brain due to overload of fluid, a condition that can lead to coma, ongoing seizures, and permanent brain injury.
• Rhabdomyolysis: Rhabdomyolysis is the rapid breakdown of muscles. This overloads the body with substances that can damage the kidneys and lead to acute kidney failure and permanent kidney damage.
• Cardiopulmonary arrest: This is when the heart and lungs suddenly stop working, leading to death. This is directly associated with cerebral edema and the effect it has on the parts of the brain that regulate these functions.

Complications of Chronic Hyponatremia

Chronic hyponatremia tends to be less severe but is insidious because it can silently damage organs over time even at milder levels. Complications include:

• Osteoporosis: Osteoporosis is the loss of bone minerals, leading to brittle and broken bones. The loss of sodium directly triggers declines in calcium levels which bones need to stay strong.
• Cerebral edema: Even mild brain swelling is associated with adverse effects over time, leading to an unsteady gait, attention deficit, changes in behavior, and an increased risk of death. It's not entirely clear if the damage is reversible and studies continue on cerebral edema's impacts.

Summary

Hyponatremia is abnormally low levels of sodium in the blood. It can be diagnosed with a blood test.

A person with hyponatremia will have no symptoms if sodium levels are mildly decreased. When sodium levels drop significantly, hyponatremia can cause headache, fatigue, nausea, vomiting, muscle cramps, and difficulty concentrating. Severe cases can lead to seizures, coma, kidney failure, and death.

Hyponatremia can have several causes, including severe diarrhea, no-salt diets, overhydration, use of diuretics, congestive heart failure, certain hormonal problems, and cirrhosis.