Hyponatremia: Causes, Symptoms, Diagnosis & Treatment

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Hyponatremia is when the amount of sodium in your blood is too low. Common causes include heart, liver, kidney and brain diseases, hormone issues and medications. Treatment could include limiting water intake, getting IV fluids and adjusting medications.

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Overview

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What is hyponatremia?

Hyponatremia is when your blood sodium (salt) level is lower than it should be. Healthcare providers consider sodium (Na+) levels below 135 milliequivalents/liter (mEq/L) to be lower than normal.

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It might seem like very little salt would be a good thing. But like many things in life, it’s all about balance. You need the right balance of water and sodium in your body to stay healthy. They can become unbalanced due to medical conditions or medications. When this happens, water moves into your tissues, causing them not to work properly. This can be especially dangerous in your brain.

If your kidneys are working as they should, drinking too much water almost never causes your blood sodium to fall too low unless you’re very dehydrated (like after running a marathon) and you don’t replace electrolytes (important minerals that keep your body working) at the same time.

Hyponatremia can be chronic or acute. Chronic hyponatremia can happen over a long time, with symptoms coming on slowly and your body making adjustments for the low sodium levels. With acute hyponatremia, blood sodium levels fall quickly, and your symptoms may become severe suddenly.

What are the types of hyponatremia?

Types of hyponatremia include:

• Euvolemic hyponatremia/dilutional hyponatremia. This is when the amount of sodium in your body stays the same but the amount of water in your body increases.
• Hypervolemic hyponatremia. This is when the amount of water and sodium in your body both increase, but the amount of water increases more.
• Hypovolemic hyponatremia. This is when the amount of water and sodium in your body both decrease, but the amount of sodium decreases more.

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Knowing which type of hyponatremia you have helps your healthcare provider diagnose the cause and determine treatment.

Symptoms and Causes

What are the symptoms of hyponatremia?

Symptoms of hyponatremia include:

• Muscle cramps or weakness
• Nausea and vomiting
• Lethargy, or extreme low energy
• Headache
• Confusion or other mental changes
• Seizures

What causes hyponatremia?

In most cases, high levels of water in your body — which dilute sodium levels — cause hyponatremia. Losing a lot of sodium from your body can also cause it (this is less common). When water and sodium levels in your body are unbalanced, fluid can move into your cells and prevent them from working properly.

Specific causes of hyponatremia include:

• SIADH (syndrome of inappropriate antidiuretic hormone secretion)
• Heart failure
• Kidney failure
• Liver cirrhosis
• Nephrotic syndrome
• Neurological conditions like brain tumors
• Excessive thirst (polydipsia)
• Hypothyroidism
• Drinking too much beer or other alcohol (beer potomania)
• Diarrhea or vomiting
• Certain medications, like diuretics (“water pills”) and SSRIs
• Nonmedical or recreational drugs, like MDMA (known as “Molly,” “E” or “Ecstasy”)

What are the risk factors for hyponatremia?

You’re more likely to develop hyponatremia if you have any of the ongoing medical conditions that cause it. Having surgery can also increase your risk.

Is hyponatremia life-threatening?

Yes. Severe hyponatremia can cause swelling in your tissues, including your brain. Untreated, this can lead to coma, permanent brain damage or death.

Diagnosis and Tests

How is hyponatremia diagnosed?

Healthcare providers use blood tests and urine (pee) tests to diagnose hyponatremia. They’ll check the levels of sodium, potassium, hormones and other substances in your body. They’ll also check how well your kidneys and liver are working. Depending on your symptoms, your provider might get imaging, like a CT scan or chest X-ray.

Your provider may ask you about:

• The kind of sports you participate in and how you train
• The kind of prescription medications you take
• The kind of medical conditions and surgeries you have or have had in the past
• The amount of alcohol you drink

Management and Treatment

How is hyponatremia treated?

Treatment for hyponatremia depends on the cause and what kind of hyponatremia you have. Treatments could include:

• Water intake restrictions
• Adjustments to your medications (like stopping them or taking a different dosage)
• IV fluids
• Medication that treat low sodium levels, like tolvaptan or conivaptan

Your provider may also treat you for ongoing medical conditions that could lead to hyponatremia.

Complications of treatment

Healthcare providers are careful not to overcorrect when treating hyponatremia. Increasing sodium levels in your body too quickly can cause life-threatening side effects, like central pontine myelinolysis or osmotic demyelination syndrome. These are types of brain damage. This is why it’s important to see a healthcare provider right away if you think you have hyponatremia.

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Outlook / Prognosis

What can I expect if I have hyponatremia?

The outlook for hyponatremia depends a lot on the cause. Many people who get quick treatment can make a full recovery. If you have brain swelling that doesn’t resolve quickly, it can lead to permanent damage.

But sometimes, hyponatremia is a sign that an ongoing medical condition is getting worse. In general, people with kidney or liver disease have a higher mortality (death) rate than people with other causes of hyponatremia.

Prevention

Can hyponatremia be prevented?

You can reduce your risk of hyponatremia by:

• Not drinking too much beer or other forms of alcohol
• Using thirst as your guide for how much water to drink (unless your provider tells you otherwise)
• Not taking MDMA
• Drinking fluids that include electrolytes (like sports drinks) instead of just water while training and during sporting events
• Talking to your provider about how to best manage medical conditions that put you at a higher risk of hyponatremia
• Eating balanced meals, including food with plenty of protein

Living With

When should I see a healthcare provider?

Talk to your provider if you have a medical condition that increases your risk for hyponatremia. They can help you manage your health and know what signs to look for.

Chronic hyponatremia may have symptoms that come on slowly, like tiredness or difficulty thinking. Talk to your provider if you notice even small changes in how you feel, especially if they get worse over time.

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When should I go to the ER?

Go to the emergency room if you or someone you know experiences:

• Confusion
• Seizures
• Difficulty waking up
• Severe headache
• Severe vomiting or diarrhea

What questions should I ask my doctor?

It might be helpful to ask a healthcare provider:

• What caused this?
• How can I avoid it in the future?
• What are early warning signs of hyponatremia?
• How do I take my medication?
• How much water should I drink each day?

Additional Common Questions

Should you eat more salt if your sodium is low?

You should follow the recommendations of a healthcare provider if your blood sodium is too low. Treatment depends on the cause, and eating too much sodium can cause additional medical issues.

A note from Cleveland Clinic

We tend to think of salt as a bad thing — but like everything, we need balance. Too little sodium can cause serious health problems. Hyponatremia is common, and most people fully recover if they’re treated right away. But many things can cause hyponatremia, so managing ongoing medical issues and medications is the best way to reduce your risk. Don’t hesitate to ask your provider if you have any questions or concerns.

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Medically Reviewed.Last updated on 11/27/2024.

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References

Cleveland Clinic’s health articles are based on evidence-backed information and review by medical professionals to ensure accuracy, reliability and up-to-date clinical standards.

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Medically Reviewed.Last updated on 11/27/2024.

References

Cleveland Clinic’s health articles are based on evidence-backed information and review by medical professionals to ensure accuracy, reliability and up-to-date clinical standards.

• Giuliani C, Peri A. Effects of Hyponatremia on the Brain (https://pubmed.ncbi.nlm.nih.gov/26237597/). J Clin Med. 2014 Oct 28;3(4):1163-77. Accessed 11/27/2024.
• Miller NE, Rushlow D, Stacey SK. Diagnosis and Management of Sodium Disorders: Hyponatremia and Hypernatremia (https://pubmed.ncbi.nlm.nih.gov/37983699/). Am Fam Physician. 2023 Nov;108(5):476-486. Accessed 11/27/2024.
• Mount DB. Fluid and Electrolyte Disturbances. In: Loscalzo J, Fauci A, Kasper D, Hauser S, Longo D, Jameson J, eds. Harrison's Principles of Internal Medicine. 21st ed. McGraw-Hill Education; 2022.
• National Kidney Foundation (U.S.) Hyponatremia (low sodium level in the blood) (https://www.kidney.org/kidney-topics/hyponatremia-low-sodium-level-blood). Last updated 11/1/2023. Accessed 11/27/2024.
• Singh P, Arora S, Singh D, et al. Hyponatremia and Outcome: Is Severity More Important Than Etiology? (https://pubmed.ncbi.nlm.nih.gov/37664323/) Cureus. 2023 Aug 1;15(8):e42808. Accessed 11/27/2024.

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