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Low sodium symptoms: What are the early signs of low sodium?

Medically reviewed by Josephine Bawab, Pharm.D.
Licensed Pharmacist
Updated Oct. 27, 2023  •  Published Feb. 28, 2023
Fact Checked
Low sodium symptoms

Overview: What does low sodium (hyponatremia) feel like?

Low sodium, or hyponatremia, occurs when the concentration of sodium in the blood is low. By itself, low sodium is not an illness, but a sign of something else. Causes of hyponatremia can be due to a variety of unrelated issues, such as drinking too much water, exercising too intensely, kidney disease, congestive heart failure, hormone problems (such as thyroid or adrenal gland problems), illegal drugs, and prescription drugs like pain medications, antidepressants, and high blood pressure drugs. 

How does low sodium feel? Most of the time, it does not feel like anything. Mild to moderate hyponatremia usually doesn’t have symptoms, especially if sodium levels have been dropping gradually. However, when sodium levels are severely low, or they drop quickly, people feel sick, though it’s hard to identify the cause. Nausea, appetite loss, feeling tired, and headaches are common symptoms that may be experienced. Muscles might get weak or start cramping. People’s moods change. They often feel agitated, restless, and quick to anger as sodium levels get too low. In the most severe cases, they can feel confused or disoriented, start convulsing, and even slip into a coma. 

If low sodium is symptomatic, medical care is needed. If symptoms of hyponatremia are severe, go to an emergency department. Fortunately, symptoms of low sodium typically go away once sodium levels return to normal. This may be quickly accomplished in some cases, but some people may need longer treatment for the underlying cause.

Key takeaways:

  • Low sodium is a common health condition that can affect anyone, regardless of age, sex, race, or ethnicity. 

  • Early signs of low sodium include tiredness, nausea, vomiting, loss of appetite, and headache.

  • Serious symptoms of low sodium, such as confusion, seizures, and coma, may require immediate medical attention.

  • Low sodium is caused by a large variety of factors, including medical conditions, prescription drugs, and sometimes just too much water intake or exercise. You may be at an increased risk for developing low sodium symptoms if you are athletic, an older adult, take certain types of prescription drugs, or have certain medical conditions, such as kidney disease, liver disease, or heart failure. 

  • Low sodium requires a medical diagnosis.

  • Treatment is generally required for symptoms of low sodium. They typically resolve within a day or two of treatment, but this could take longer in severe cases.

  • Treatment of low sodium may include fluid restriction, increased sodium intake, IV fluids, or hyponatremia drugs. The underlying cause may also require treatment. 

  • Untreated low sodium could result in complications, such as muscle damage, brain swelling, irreversible nerve damage, brain stem damage, respiratory arrest, and death.

  • Use coupons for hyponatremia treatments like furosemide, levothyroxine, and prednisone to save up to 80%.

What are the early signs of low sodium?

Almost any of the signs of low sodium can happen early. Low sodium typically does not have symptoms unless the condition is severe or it happens very quickly. If sodium levels drop rapidly, some of the early signs could be severe symptoms. 

Some of the most common signs of low sodium are:

  • Nausea

  • Headache

  • Feeling tired

  • Dizziness

  • Muscle problems like cramps or weakness

Other low sodium symptoms

Other symptoms of low sodium include:

  • Nausea

  • Headache

  • Dizziness

  • Lethargy

  • Vomiting

  • Loss of appetite

  • Agitation

  • Restlessness

  • Irritability

  • Confusion

  • Balance or coordination problems

  • Reduced consciousness

  • Seizures

  • Slowed breathing

  • Coma

Low sodium symptoms

Hyponatremia vs. hypernatremia symptoms

Too much sodium in the blood, or hypernatremia, is the opposite of hyponatremia. Typically, people get low blood sodium when there’s too much water in the blood. On the other hand, the most common cause of high blood sodium levels is dehydration. When the body doesn’t have enough water,  sodium concentrations become high. The symptoms of hyponatremia and hypernatremia are largely the same, so it’s easy to confuse the two of them. It helps to know that one of the defining symptoms of high sodium is usually thirst.

Hyponatremia Hypernatremia
Shared symptoms
  • Muscle weakness
  • Lethargy
  • Restlessness
  • Irritability
  • Vomiting
  • Loss of appetite
  • Confusion
  • Reduced consciousness
  • Seizures
  • Coma
Unique symptoms
  • Slowed breathing
  • Balance problems
  • Extreme thirst
  • Reduced urination
  • Muscle twitches

Sources: 

Types of low sodium: How can I tell which one I have? 

There are several types of low sodium. They are all based on how much water is in the blood and how much sodium is dissolved in that water. A healthcare provider can tell what type of hyponatremia is present by doing blood tests. Determining the type helps the doctor pin down its cause and find the most suitable treatment.

Context also plays a big role in determining the type of hyponatremia present. If a person drinks too much beer and starts showing low sodium symptoms, the doctor will probably diagnose  it as “hypotonic euvolemic hyponatremia.” All that person needs to know is to stop drinking fluids for a while and then take it a bit slower the next time. Drinking electrolytes may help as well. Taking an antidepressant could cause the body to hold excess water (called SIADH) and may also cause hypotonic euvolemic hyponatremia.

When to see a doctor for low sodium symptoms

If low sodium levels are suspected, see a doctor for a definitive diagnosis. Although the problem may be minor and easily resolved, it could be something more serious. It helps to be aware of risk factors. Certain medical conditions, like kidney disease and heart failure, may make low sodium more likely. Prescription drugs, athletic activity, drinking too much water, and hormone problems can also increase the risk of low sodium. In those cases, be familiar with the signs of low sodium and get medical help if they’re experienced. If severe symptoms, such as confusion, reduced consciousness, falls, seizures, or coma, are experienced, emergency medical care is needed. 

To diagnose low sodium and its cause, the doctor will perform a thorough medical history and physical exam. Be ready to answer questions about:

  • All the symptoms being experienced

  • All medical conditions, particularly lung or central nervous system conditions

  • Any drugs or supplements being taken

  • Lifestyle habits, such as exercising, drinking, or using illegal drugs

A blood test is needed to definitively diagnose low sodium. Blood volume, concentration of particles in the blood, and sodium blood levels will be measured. A urine test will also be required to measure the concentration of particles and the amount of sodium in the urine. To determine a cause, the doctor may also test the blood for certain hormones, cholesterol, glucose, or liver enzymes. In some cases, a CT scan of the head or abdomen may be required.

Complications of low sodium

Severe low sodium can result in serious or life-threatening complications, such as:

  • Muscle damage

  • Seizures

  • Brain swelling

  • Permanent nerve or brain damage, including a severe complication of over-treatment, called osmotic demyelination syndrome

  • Respiratory arrest

  • Death

Sources:

How to treat low sodium symptoms

Although symptoms of low sodium are common and usually mild, low sodium could be due to a more serious underlying problem. It’s important to see a doctor to figure out if the symptoms present any cause for worry, especially if you have reason to believe you’re at risk for low sodium. Because the symptoms of low sodium could be something else, make sure to list the symptoms and account for all current medical conditions and drugs being taken. Don’t start trying to fix the problem until you’ve seen a doctor. 

Hyponatremia treatment will vary depending on the cause. The simplest treatment is to rid the body of free water by restricting fluid intake. In some cases, people may need to put more sodium in their diet. Intravenous fluids or prescription drugs for hyponatremia may be required in chronic or severe situations. 

Other situations may require more effort, particularly in people with hyponatremia due to serious illnesses such as heart failure, liver failure, cirrhosis of the liver, or kidney disease. In those cases, prescription diuretics (“water pills”), such as Lasix (furosemide) or Bumex (bumetanide), may be required. For hormone disorders, people may need replacement hormone therapy like thyroid hormones, such as Synthroid (levothyroxine), for hypothyroidism or corticosteroids, such as prednisone or dexamethasone, for Addison’s disease.

Signs low sodium is getting better

Low sodium can often be corrected within a few days. Even the most severe cases might be correctable with just a couple of days of fluid restriction or intravenous solutions. As sodium returns to normal, the symptoms will fade. People will feel more alert, feel more energetic, and have fewer aches and muscle problems.

Most importantly, see a doctor

Low levels of sodium can be a sign of an array of possible problems. Some may be trivial and easily fixable. Others may be far more serious, such as heart failure or hormone imbalances. If low sodium is suspected, always get medical advice from a healthcare professional. Low sodium can only be diagnosed through blood and urine tests, not from the symptoms. Only a doctor can determine if the problem is temporary (acute hyponatremia) or constant (chronic hyponatremia), why sodium levels are low, and how best to treat the problem.

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FAQs about low sodium symptoms

What happens when your body is low on sodium?

Sodium is a vital electrolyte that helps the body regulate water levels and maintain the proper functioning of nerves and muscles. When the concentration of sodium in the blood is too low, nerves and muscles don’t work as well as they should. 

Why does low sodium cause seizures?

Normally, low sodium slows down nerves. Sodium is one of the electrolytes—along with calcium, potassium, and magnesium—responsible for producing the electrical charge of a nerve. Seizures are rarely, if ever, a problem with mild or moderate cases of hyponatremia. However, severe hyponatremia disrupts electrolytes moving in and out of nerve cells based on the concentration of electrolytes in the body’s water, so 30% of people with severe hyponatremia will experience seizures, usually convulsions.

Sources:

Why is sodium low in renal failure?

When people have kidney failure, the kidneys stop removing free water from the blood. As the amount of water increases in the blood, the sodium concentration goes down. 

What are the symptoms of low sodium and potassium?

Low sodium and low potassium have similar symptoms, including fatigue, muscle weakness, and muscle cramps. However, potassium is important for the proper functioning of the heart, smooth muscles, and peripheral nerves. Therefore, low potassium also causes symptoms like heart palpitations, constipation, reduced blood pressure, and tingling or numbness in the hands or feet.

What’s next? Additional resources for people with low sodium symptoms

Test and diagnostics

Treatments

Scientific studies and clinical trials

Medically reviewed by Josephine Bawab, Pharm.D.
Licensed Pharmacist

Josephine Bawab, Pharm.D., graduated from Virginia Commonwealth University School of Pharmacy. She began working in community pharmacy in 2012 and has worked for multiple chain pharmacies since then. She is passionate about helping patients and precepting students. She currently works and resides in Virginia, where she is just a few minutes away from the beach.

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