Hyponatremia: Which disease is caused by deficiency of salt?

November 4, 2025 •

4 min read

Hyponatremia, the clinical term for a blood sodium level below 135 mEq/L, is the disease caused by deficiency of salt and is the most common electrolyte abnormality. While often associated with dehydration, it is more commonly caused by overhydration or underlying medical conditions that disrupt the body's fluid balance.

Quick Summary

Hyponatremia, or low blood sodium, is a serious electrolyte imbalance that can cause symptoms ranging from mild fatigue to seizures and coma. Causes include fluid dilution from overhydration, medical conditions like heart and kidney disease, and certain medications. Management depends on the root cause and severity.

Key Points

Hyponatremia is the disease caused by a severe deficiency of salt or sodium. This common electrolyte imbalance can range from mild and asymptomatic to severe and life-threatening.
Causes are diverse and often related to fluid imbalance. Hyponatremia frequently results from excess water intake (overhydration) or underlying medical conditions like heart, kidney, and liver diseases, rather than just low dietary salt.
Symptoms vary from mild to severe. Early signs include nausea, headaches, and fatigue, while severe cases can lead to confusion, seizures, coma, and brain swelling.
Diagnosis relies on blood and urine tests. A healthcare professional can confirm hyponatremia by measuring your blood sodium levels and can use other tests to determine the cause.
Treatment depends on the cause and severity. Options range from fluid restriction and medication adjustments for chronic cases to emergency intravenous saline for acute, severe hyponatremia.
Prevention is possible through informed hydration. Athletes and individuals with risk factors should focus on replacing lost electrolytes, not just water, and manage any pre-existing medical conditions.

Understanding Hyponatremia: The Disease Caused by Deficiency of Salt

Hyponatremia, defined as a low concentration of sodium in the blood (serum sodium concentration of less than 135 mEq/L), is the primary medical condition stemming from a severe deficiency of salt. Sodium, a crucial electrolyte, is essential for maintaining fluid and blood volume, proper nerve signaling, and muscle function. While a poor diet lacking salt can contribute, a true dietary-only deficiency is rare in healthy individuals due to its prevalence in processed foods. More often, hyponatremia results from a complex imbalance of water and sodium caused by medical conditions or lifestyle factors. When the ratio of water to sodium becomes skewed, water moves into the body's cells, causing them to swell. This is particularly dangerous for brain cells, as swelling can lead to severe neurological symptoms and, in extreme cases, be fatal.

Common Causes of Low Sodium Levels

The causes of hyponatremia are categorized based on the body's fluid volume status: hypovolemic (low volume), hypervolemic (high volume), and euvolemic (normal volume).

Hypovolemic Hyponatremia: Occurs from a significant loss of both water and sodium, with sodium loss being greater. It can be caused by:

Gastrointestinal fluid loss: Severe vomiting or diarrhea.
Excessive sweating: From intense physical activity without proper electrolyte replenishment.
Diuretics: Certain medications, especially thiazide diuretics, can increase urine output and sodium excretion.

Hypervolemic Hyponatremia: Involves an increase in both total body sodium and water, but the water gain is greater, leading to dilution. It is often seen with:

Heart failure: The heart's inefficiency leads to fluid retention.
Cirrhosis: Advanced liver disease causes fluid buildup.
Kidney diseases: Conditions like chronic kidney disease impair the kidneys' ability to excrete fluid.

Euvolemic Hyponatremia: The body's total water increases while sodium content remains relatively normal. Common causes include:

Syndrome of inappropriate antidiuretic hormone secretion (SIADH): Causes the body to retain too much water.
Drinking too much water: Excessive water intake, particularly during endurance sports, can overwhelm the kidneys.
Addison's disease: Adrenal gland insufficiency affects hormones that regulate water and electrolyte balance.
Certain medications: Antidepressants and some pain medicines can interfere with sodium levels.

Recognizing the Symptoms of Hyponatremia

Symptoms can vary widely depending on the severity and speed of the sodium drop. Mild hyponatremia may be asymptomatic, while severe or acute cases can present life-threatening symptoms.

Mild to Moderate Symptoms:

Nausea and vomiting
Headaches
Fatigue and lethargy
Loss of energy and appetite
Muscle weakness or cramps

Severe Symptoms:

Confusion, restlessness, and irritability
Altered mental status or decreased consciousness
Seizures
Coma
Brain swelling, which can be fatal

Diagnosis and Treatment Options

Diagnosing hyponatremia typically involves a physical examination and laboratory tests to measure blood sodium levels. Urine tests can also help determine the underlying cause by evaluating sodium excretion. A comprehensive metabolic panel may be ordered to assess kidney and liver function.

Treatment is highly individualized and depends on the underlying cause, severity, and duration of the condition. For mild, chronic cases, a doctor may recommend simple lifestyle changes, but more severe instances require aggressive medical intervention.

Treatment strategies often include:

Fluid Restriction: Limiting water intake is a common approach for euvolemic and hypervolemic hyponatremia.
Intravenous (IV) Saline: For severe or acute hyponatremia, hypertonic saline may be administered to slowly raise sodium levels under careful supervision.
Medication Adjustments: A doctor may stop or change medications that are causing the imbalance.
Treating the Underlying Cause: Managing the primary condition, such as heart or kidney disease, is essential for long-term correction.
Electrolyte Replacement: In cases of true sodium loss from the body, oral salt tablets or electrolyte-rich sports drinks may be used.

Comparison of Acute vs. Chronic Hyponatremia


Feature	Acute Hyponatremia	Chronic Hyponatremia
Onset	Occurs rapidly, within 48 hours	Develops gradually, over 48 hours or longer
Symptoms	Symptoms appear quickly and tend to be more severe, including brain swelling, seizures, and coma	Symptoms are typically more mild or absent, as the brain has time to adapt
Risks	Higher risk of rapid, dangerous brain swelling if untreated	Overly rapid correction can cause osmotic demyelination syndrome, a severe neurological condition
Treatment Speed	Can be corrected more quickly, especially in symptomatic cases	Correction must be done very slowly to prevent complications

Prevention and When to See a Doctor

Preventing hyponatremia involves careful attention to fluid intake, especially for individuals at higher risk. Following your doctor's guidance on fluid restrictions for existing conditions is critical. Athletes engaged in prolonged, intense activity should consume sports drinks containing electrolytes to replace lost sodium, rather than just plain water. Using thirst as a guide for hydration can also help prevent overhydration, unless advised otherwise by a medical professional.

It is vital to seek immediate medical attention for severe symptoms like confusion, seizures, or loss of consciousness. For milder, persistent symptoms such as ongoing fatigue or headaches, it is still important to consult a healthcare provider for evaluation and to determine the underlying cause. For more detailed medical information, the Mayo Clinic provides comprehensive resources on hyponatremia.

Conclusion: The Critical Role of Balanced Sodium

While we often hear about the dangers of high salt intake, the disease caused by deficiency of salt—hyponatremia—is a serious and potentially life-threatening condition. Proper sodium levels are vital for a host of bodily functions, and an imbalance can have widespread effects, especially on the brain. Maintaining a healthy electrolyte balance requires managing underlying medical conditions, being mindful of fluid intake, and consulting with healthcare professionals, particularly during illness or intense exercise. Understanding the causes, recognizing the symptoms, and seeking timely and appropriate treatment are key to preventing the most severe consequences of this electrolyte disorder.

Disclaimer: This article is for informational purposes only and does not constitute medical advice. Consult a healthcare provider for any health concerns or before making changes to your diet or medication.

Frequently Asked Questions

The medical term for the disease caused by a deficiency of salt (sodium) is hyponatremia. It is defined as having a blood sodium level below 135 mEq/L and can be triggered by a variety of factors, including medical conditions and fluid imbalances.

Early or mild signs of low sodium often include nausea, vomiting, headaches, a general loss of energy, and muscle cramps or weakness.

Yes. Drinking excessive amounts of water, especially during endurance activities or for a prolonged period, can cause low sodium levels by diluting the sodium content in your blood. This is a common cause of hyponatremia.

Hyponatremia is diagnosed by a healthcare provider using a simple blood test called a serum sodium test. Depending on the results, further blood and urine tests may be ordered to identify the underlying cause.

Treatment varies based on the cause and severity. It can involve fluid restriction, adjustment of medications, or, in severe cases, administering intravenous saline solution. For cases caused by excessive sweating, oral electrolyte replacement may be used.

If left untreated, severe hyponatremia can lead to dangerous complications such as brain swelling (cerebral edema), seizures, coma, and even death. It is a medical emergency requiring prompt treatment.

Athletes engaged in prolonged or intense exercise can prevent low sodium levels by consuming sports drinks that contain electrolytes, not just plain water, to replace the sodium lost through sweat.

While recommendations can vary, a common guideline is to limit daily salt intake to less than 5 grams, which is equivalent to about 2,000 mg of sodium. Individual needs, especially for those with medical conditions, should be discussed with a doctor.