How Lack of Sodium Makes You Feel: The Symptoms of Hyponatremia

December 8, 2025 •

2 min read

According to the Merck Manuals, hyponatremia, or low blood sodium, is defined as a serum sodium concentration of less than 135 mEq/L. A lack of sodium can make you feel unwell, causing a range of symptoms from subtle fatigue and confusion to more severe and life-threatening issues, as sodium is a critical electrolyte for proper bodily functions.

Quick Summary

This article explores the effects of insufficient sodium, detailing the various symptoms of hyponatremia and the underlying causes. It outlines the health risks associated with low sodium levels and provides practical advice for prevention and management.

Key Points

Fatigue and Headaches: One of the earliest and most common signs of a lack of sodium is general fatigue, weakness, and persistent headaches.
Neurological Effects: Low sodium levels can cause serious neurological issues, including confusion, brain fog, irritability, and in severe cases, seizures and coma.
Muscle Function Impairment: Sodium is essential for muscle contraction, so a deficiency can lead to painful muscle cramps, weakness, and spasms.
Cell Swelling: The dangerous symptoms of acute hyponatremia are caused by excess water moving into and swelling the body's cells, a process most critical in the brain.
Causes Vary: Hyponatremia can be caused by drinking too much plain water, excessive sweating, certain medications, or underlying health issues like heart, kidney, and liver disease.
Prevention is Key: To prevent low sodium, pay attention to thirst during exercise, consider electrolyte-rich drinks during prolonged activity, and manage underlying health conditions with medical supervision.

The Crucial Role of Sodium in Your Body

Sodium, an essential electrolyte, is vital for numerous bodily functions, including regulating fluid balance, blood pressure, muscle contractions, and nerve function. Maintaining a delicate balance is crucial, as both excessive and insufficient sodium levels can be detrimental to health. A lack of sodium leads to hyponatremia, characterized by blood sodium levels below 135 to 145 mEq/L.

Symptoms of Low Sodium

Symptoms of hyponatremia can range from mild to severe. Mild to moderate effects may include headaches, fatigue, nausea, vomiting, muscle cramps, and difficulty concentrating. Severe drops in sodium can cause life-threatening symptoms due to brain cell swelling. These require immediate medical attention and include severe confusion, seizures, coma, and brain swelling.

Causes and Risk Factors for Low Sodium

Hyponatremia can be caused by various factors. Underlying medical conditions like kidney disease, heart failure, and hormonal issues such as Addison's disease can contribute. Lifestyle factors like excessive sweating, drinking too much water without electrolytes, and very low-sodium diets also play a role. Certain medications, including diuretics and some antidepressants, can affect sodium levels.

Comparison of Sodium Imbalances: Hyponatremia vs. Dehydration

It's important to distinguish between low sodium and dehydration. Hyponatremia involves a low concentration of sodium in the blood, potentially with varying fluid volumes, while dehydration is primarily a loss of total body water. Thirst is typical in dehydration but not always present in hyponatremia. Treatment for hyponatremia focuses on addressing the cause and managing fluid and sodium levels, potentially including IV sodium, whereas dehydration is treated with fluid replacement.

How to Prevent Hyponatremia

Prevention involves balanced hydration and managing health. Drink according to thirst, especially during exercise, and consider electrolyte replacement during prolonged activities. Managing underlying conditions and reviewing medications with a doctor are also crucial preventive steps. A balanced diet provides adequate sodium.

Conclusion

Low sodium levels (hyponatremia) can cause symptoms ranging from mild fatigue to severe neurological issues due to its vital role in bodily functions. Causes include medical conditions, lifestyle factors, and medications. Severe cases are medical emergencies requiring prompt treatment. Preventing hyponatremia involves careful hydration and health management. Consulting a healthcare professional is essential if low blood sodium is suspected.

Frequently Asked Questions

The first signs of low sodium often include mild, non-specific symptoms such as fatigue, persistent headaches, muscle cramps, and a general feeling of being 'off' or unwell.

Yes, low sodium, or exercise-associated hyponatremia, is a risk for endurance athletes. It is often caused by overconsuming plain water during long, intense exercise while losing sodium through sweat, which dilutes the body's sodium levels.

Yes, drinking too much water, especially in a short period, can significantly dilute the sodium concentration in the blood, leading to hyponatremia. This is a common cause, particularly in endurance sports.

While both involve fluid imbalance, hyponatremia is defined by a low sodium concentration in the blood, which can occur with normal, low, or even high fluid volume. Dehydration is specifically a loss of total body water. Their treatments are also distinct.

You should seek emergency medical care for severe symptoms such as confusion, seizures, or lost consciousness. For milder symptoms like persistent nausea, headaches, or muscle cramps, it's wise to call your healthcare provider, especially if you are at a higher risk.

A variety of conditions can cause low sodium, including kidney diseases, heart failure, cirrhosis, adrenal gland insufficiency, hypothyroidism, and the syndrome of inappropriate antidiuretic hormone secretion (SIADH).

The treatment approach depends on the severity and cause. For mild cases, your doctor may recommend consuming more salty foods or an electrolyte drink. For severe, acute cases, intravenous sodium solutions are administered in a hospital setting with close monitoring.