An Overview of Low Sodium Levels

What to Know About Hyponatremia

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It is not common to have a low sodium level. That is because sodium is a mineral that we consume in salt—and the vast majority of people consume far more sodium than they need. Even as your sodium intake fluctuates from day to day, your body does a pretty good job of maintaining the right concentration of sodium in the body.

However, sodium levels can sometimes be decreased due to illness or dietary habits, leading to a condition known as hyponatremia (low blood sodium). Depending on how low the sodium levels are, symptoms can range from mild to severe.

Spilt over salt shaker on table
Jose Luis Agudo / Eye Em / Getty Images 

This article looks at the symptoms and causes of hyponatremia. It also explains how the condition is defined, diagnosed, and treated.

Symptoms of Hyponatremia

Sodium is an essential mineral, meaning that your body can't make it. The only way to get it is through food. If you don't get enough and levels start to drop, hyponatremia can occur.

Many people with mild hyponatremia may be asymptomatic (without symptoms). However, as sodium levels continue to decline, the incidence and severity of symptoms can increase.

Symptoms of hyponatremia may include:

  • Headaches
  • Fatigue
  • Irritability
  • Loss of balance
  • Loss of appetite
  • Trouble concentrating
  • Profuse or sudden sweating
  • Nausea and vomiting
  • Cramps
  • Seizures
  • Loss of consciousness
  • Coma

Complications

Hyponatremia can affect the function of your thyroid gland. The thyroid gland works by producing hormones that regulate metabolism, heart rate, digestion, and other bodily functions.

Our body needs dietary iodine to make thyroid hormones, and much of it comes from the iodized salt we eat. If you have hyponatremia for a prolonged period, you are likely to have symptoms of hypothyroidism as well, including:

Recap

The symptoms of hyponatremia range from mild to severe based on how low your sodium levels are. Mild cases may cause headache and fatigue, while severe hyponatremia can lead to seizures and coma. Hypothyroidism (low thyroid function) may also occur.

Causes

Low sodium can result from lifestyle factors and medical conditions that affect the balance of water and/or sodium in the body.

Lifestyle Factors

Dietary and lifestyle issues rarely affect sodium levels. Even so, the rapid loss of fluid and/or the excessive intake of fluid can cause sodium concentrations to plummet.

Excessive sweating can cause the rapid loss of sodium. 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 can drop even further. This is because you are diluting the amount of sodium per volume of water in the body.

It is also possible to get hyponatremia through extreme sodium-free diets. Drinking too much water (overhydration) only increases the risk.

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 aldosterone which balances sodium and potassium in the body. Adrenal insufficiency, also known as Addison's disease, disrupts this balance.
  • Cerebral salt wasting syndrome (CSWS): This rare condition caused by a brain injury alters the function of the kidneys, causing them to clear excessive amounts of sodium from the body.
  • Congestive heart failure: The inability of the heart to efficiently pump blood through the body can cause fluid build-up, leading to hyponatremia.
  • Diarrhea: Severe diarrhea can lead to a condition called hypovolemia in which the extreme loss of fluid can lead to hyponatremia, low blood pressure, and, in severe cases, shock.
  • Diuretics: "Water pills" used to bring down blood pressure can affect the balance of water and sodium in the body. Diuretics can lead to hyponatremia if electrolytes are not replenished.
  • Liver cirrhosis: The scarring of the liver can cause fluid retention. The level of retention increases in tandem with the severity of liver damage.
  • Syndrome of inappropriate antidiuretic hormone hypersecretion (SIADH): Antidiuretic hormone (ADH) prevents the body from losing too much water in the urine. SIADH causes the body to hold onto too much water, leading to hyponatremia.

Recap

Hyponatremia is caused when there is an imbalance between water and sodium levels in the body. Causes include severe diarrhea, extreme sodium-free diets, overhydration, diuretics, congestive heart failure, liver cirrhosis, and hormonal dysfunction.

Diagnosis

Hyponatremia is diagnosed with a physical exam, laboratory 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.

The doctor will also check for neurological (central nervous system-related) problems such as a loss of alertness, concentration, or orientation.

Recap

Hyponatremia is diagnosed with a physical exam, a review of your medical history, and lab tests. Hyponatremia is defined as having a blood sodium level lower than 135 mEq/L.

Treatment Options

The treatment of hyponatremia can be simple at times and challenging at others. The treatment is often based on the slow and careful replacement of sodium in the body, as well as the management of the underlying cause of hyponatremia.

Dietary Intake

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

Keep in mind that the salt in processed foods, bread, pasta, sauces, and even desserts counts towards the daily recommended intake.

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.

Intravenous Replacement

If you have severe hyponatremia, you may need sodium to be replaced with intravenous (IV) fluids. The IV fluid will contain water, sodium, and other key electrolytes.

The medical team will restore the sodium level over the course of several hours or days, depending on the severity of your condition. A too-rapid infusion of sodium can lead to osmotic demyelination syndrome (ODS), a form of brain damage.

Medications

There are few medications that are consistently effective in treating hyponatremia. Drugs called vasopressin receptor antagonists are 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, liver 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 sun sensitivity in some.

Recap

Mild cases of hyponatremia may be treated with increased dietary salt intake. Severe cases may require intravenous (IV) sodium replacement delivered over hours or days.

Summary

Hyponatremia is abnormally low levels of sodium in the blood. Oftentimes 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 or coma.

Hyponatremia is caused by an imbalance of sodium and water in the body. Causes include severe diarrhea, no-salt diets, overhydration, diuretics, congestive heart failure, and cirrhosis of the liver. Hormonal dysfunction such as adrenal insufficiency and syndrome of inappropriate antidiuretic hormone hypersecretion (SIADH) are also common causes.

Hyponatremia can be diagnosed with a blood test. A physical exam and review of your medical history can help reveal the underlying cause. The treatment of low blood sodium may involve increased dietary salt intake for mild cases and intravenous sodium replacement for severe ones.

A Word From Verywell

Hyponatremia has many causes, some of which are more serious than others. If you have symptoms of hyponatremia, it's important to see a doctor. The cause may be due to dietary issues that can be easily resolved, but the symptoms may also be the first sign of a serious medical condition.

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7 Sources
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