Why is low-sodium a concern for your health?

December 13, 2025 •

3 min read

Hyponatremia, the medical term for low blood sodium, is the most common electrolyte disorder, affecting as many as 20–35% of hospitalized patients. While sodium often receives negative attention for its role in high blood pressure, insufficient levels can be equally, if not more, dangerous, causing cells to swell and affecting vital bodily functions.

Quick Summary

This article explains why low blood sodium, or hyponatremia, is a serious concern, detailing the risks of cellular swelling, especially in the brain. It covers the wide range of mild and severe symptoms, identifies major causes such as kidney disease and excessive fluid intake, and outlines treatment options.

Key Points

Hyponatremia is low blood sodium. It is the most common electrolyte disorder, frequently seen in hospitalized patients.
Low sodium causes cellular swelling. This is particularly dangerous for brain cells, potentially leading to cerebral edema and neurological damage.
Hyponatremia can be acute or chronic. Acute, rapid drops are more severe, while chronic, slow development leads to milder but still significant long-term effects.
Causes often involve fluid imbalance. Excessive water intake, medical conditions (heart, kidney, liver disease), and certain medications are common culprits.
Symptoms range from mild to life-threatening. Mild symptoms include headache and nausea; severe symptoms like confusion, seizures, and coma require emergency care.
Treatment is tailored to the cause and severity. Options range from fluid restriction to IV sodium administration, always under medical supervision.
Prevention focuses on balanced hydration. Thirst guidance and electrolyte drinks during intense exercise are recommended for at-risk individuals.

Understanding the Role of Sodium

Sodium is a crucial electrolyte vital for maintaining water balance in and around body cells. It helps regulate blood pressure and is essential for nerve, muscle, and tissue function. Normal blood sodium levels are typically 135 to 145 milliequivalents per liter (mEq/L). When levels fall below 135 mEq/L, this electrolyte imbalance, known as hyponatremia, can lead to serious health issues.

The Dangerous Effects of Cellular Swelling

Low blood sodium causes water to move into cells to balance electrolyte concentrations, leading to cellular swelling. The brain is particularly vulnerable to this swelling because the skull offers no room for expansion. This cerebral edema can increase pressure within the skull, impairing brain function and potentially causing severe neurological damage.

Acute vs. Chronic Hyponatremia

Hyponatremia can develop rapidly (acute) or slowly over time (chronic), influencing symptom severity and risk.

Acute Hyponatremia: Rapid decline in sodium within 48 hours. Brain cells have less time to adapt, leading to sudden, severe symptoms like brain swelling, coma, or death. This requires emergency medical attention. Individuals who overhydrate with plain water (like endurance athletes) and users of certain illicit drugs are at higher risk.
Chronic Hyponatremia: Develops slowly over days or weeks, allowing the brain to adapt. Symptoms are generally milder but still significant, linked to long-term issues like impaired balance and attention deficits, increasing fall and fracture risks, especially in older adults.

Common Causes of Low Blood Sodium

Low sodium levels are frequently a result of underlying medical conditions or imbalances in water and sodium, not just a low-sodium diet.

Excessive Water Intake: Consuming large amounts of water can dilute blood sodium to dangerous levels, especially in endurance athletes who only replace fluids with water, or rarely, in individuals with certain psychiatric conditions.
Medical Conditions: Several health issues disrupt fluid and electrolyte balance, including:
- Congestive heart failure, causing fluid buildup.
- Advanced kidney disease and liver cirrhosis, impairing fluid excretion.
- Syndrome of Inappropriate Antidiuretic Hormone (SIADH), leading to water retention.
- Adrenal gland disorders (Addison's disease) or hypothyroidism.
Medications: Certain drugs, such as diuretics, some antidepressants (SSRIs), and specific pain medications, can affect sodium balance.
Excessive Fluid Loss: Severe or prolonged vomiting, diarrhea, or extensive burns can cause significant loss of sodium and water.

Low-Sodium Symptoms: What to Watch For

Symptoms of hyponatremia vary from mild to severe and can be mistaken for other conditions, particularly when developing slowly.

Table: Mild vs. Severe Symptoms of Hyponatremia


Mild Symptoms	Severe Symptoms (Require Immediate Medical Attention)
Nausea and vomiting	Altered mental status and severe confusion
Headache	Seizures and convulsions
Low energy, fatigue, or drowsiness	Loss of consciousness or coma
Restlessness and irritability	Hallucinations
Muscle weakness, cramps, or spasms	Brain herniation

Navigating Treatment and Prevention

Treatment depends on the cause, severity, and how quickly hyponatremia developed, and must be supervised by a healthcare professional.

Addressing the Root Cause: For moderate, chronic cases, a doctor may advise adjusting fluid intake or medications. Managing the underlying medical condition is key.
Emergency Intervention: Severe, acute hyponatremia with neurological symptoms requires immediate hospital care. Treatment may involve intravenous saline to gradually raise sodium levels, carefully monitored to prevent rapid correction risks.
Preventative Measures: At-risk individuals, like athletes or those with chronic conditions, may be advised to use thirst as a hydration guide, use electrolyte-containing sports drinks during prolonged exercise, monitor sodium levels if taking certain medications, and maintain a balanced diet.

Conclusion: Finding the Right Balance

Recognizing the dangers of both too much and too little sodium is important for health. Hyponatremia, while sometimes linked to diet, is often a symptom of underlying medical issues or fluid imbalances. Prompt medical attention for symptoms, especially severe ones, is crucial. Maintaining a proper balance of fluids and electrolytes is vital for many bodily functions. Consult a healthcare professional if you have concerns about your sodium intake or electrolyte balance.

Important Safety Note

Discuss any changes to your diet or fluid intake with a healthcare professional, especially if you have existing medical conditions. This information is for educational purposes only and is not medical advice.

Frequently Asked Questions

The primary danger of low sodium, a condition called hyponatremia, is that it causes water to move into cells, making them swell. This is particularly dangerous for brain cells, which can lead to cerebral edema, increased pressure on the brain, and severe neurological problems.

Mild low sodium may present with non-specific symptoms such as headache, nausea, fatigue, irritability, and muscle cramps. These symptoms often develop slowly in cases of chronic hyponatremia.

You should seek immediate emergency medical care if you experience severe symptoms such as confusion, seizures, hallucinations, loss of consciousness, or a rapid onset of severe symptoms. For milder or gradual symptoms, contact a healthcare professional for diagnosis and guidance.

Yes, drinking excessive amounts of plain water can dilute the sodium in your blood, especially if you are also losing sodium through sweat. This is a particular risk for endurance athletes and can lead to a condition known as water intoxication.

A variety of medical conditions can cause low sodium, including congestive heart failure, kidney disease, cirrhosis of the liver, and endocrine disorders like Addison's disease or SIADH (Syndrome of Inappropriate Antidiuretic Hormone).

Treatment varies depending on the cause and severity. It can involve fluid restriction, adjusting medications, or, in severe cases, administering intravenous sodium solutions in a hospital setting with careful monitoring. The underlying cause is also addressed as part of the treatment.

Prevention strategies include drinking fluids according to thirst, consuming sports drinks with electrolytes during intense or prolonged physical activity, and managing any underlying medical conditions that could affect sodium balance. If you take medication that affects sodium levels, regular monitoring is advised.