The short answer
Sodium helps your nerves and muscles work and keeps your body's fluids balanced. A low blood level is called hyponatremia. It can come from vomiting or diarrhea, fluid build-up from heart, liver or kidney disease, some cancers and some medicines. Symptoms can include weakness, tiredness and confusion.
Sodium helps nerves and muscles work and keeps fluids in balance.
Low sodium in the blood is called hyponatremia.
Causes include vomiting, diarrhea, some medicines, some cancers and heart, liver or kidney disease.
Symptoms can include weakness, tiredness, confusion and muscle twitching.
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The short version
Sodium is a mineral in your blood. MedlinePlus says it helps your nerves and muscles work properly and keeps your body's fluids in balance. A low sodium level is called hyponatremia.
What can cause low sodium
MedlinePlus lists several causes:
- Losing sodium through diarrhea or vomiting.
- Conditions that make the body hold on to fluid, such as kidney disease, liver cirrhosis and heart failure.
- Certain brain and lung conditions.
- Some cancers.
- Some medicines, including some pain relievers and some antidepressants.
- Addison disease and malnutrition.
Symptoms to know
Low sodium can cause weakness, tiredness, confusion and muscle twitching. It can cause seizures, and severe cases that are not treated can lead to coma. Call 911 or go to the emergency room for a seizure or sudden confusion. Call your care team about new or worse symptoms.
Reading your result
Ranges are not the same at every lab. MedlinePlus notes that a result outside the normal range does not always mean you need treatment. Do not change how much water you drink or salt you eat without asking. The right step depends on the cause.
What to ask
Ask what is causing the low level and whether a medicine may be involved. Your team reads this number alongside your other results and symptoms.
Sources
Common questions
What causes low sodium?
MedlinePlus lists losing sodium through diarrhea or vomiting, and conditions that make the body hold on to fluid, such as kidney disease, liver cirrhosis and heart failure. Certain brain and lung conditions, some cancers, and some medicines, including some pain relievers and antidepressants, can also cause it.
What are the symptoms?
MedlinePlus lists weakness, tiredness, confusion, muscle twitching and seizures. Severe low sodium that is not treated can lead to coma. Get emergency help for a seizure or sudden confusion.
Does an out-of-range result always need treatment?
No. MedlinePlus notes that a result outside the normal range does not always mean you have a condition that needs treatment. Your care team reads it with your other results.
Should I drink more water or eat more salt?
Do not change how much you drink or eat salt without asking. The right step depends on the cause.
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Sources last checked: 2026-10-02 what this meansLast updated: 2026-09-27Next planned review: 2027-09-27
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Cancer Explained does not originate medical claims. Every page restates guidance already published by the National Cancer Institute, the CDC, the USPSTF and the FDA, in plain language, with the source cited so you can check the original yourself. AI does the translating and organizing; automated checks test claims, citations, clarity and safety before anything publishes, and this is translation and navigation, not clinical judgment. Nothing here is personal medical advice, and no page can account for your particular situation.
Editorial status: Source checked — This page was written with AI assistance and then compared with the sources listed on it, looking for statements those sources do not back up. That check is not a sentence-by-sentence record and can miss errors. It is not a medical review, and it does not confirm the page is complete or right for your situation.
Human medical review: not completed. Pages here are not signed off by a clinician before they publish. That is not an oversight we are quietly working around: we restate published guidance and cite it, so the authority belongs to the source rather than to us, and every page names where its claims come from — you can verify us instead of trusting us. Where a volunteer clinician has reviewed a page, their name and credentials appear on it; where no name appears, no clinician has checked it. We are glad to have reviewers and are recruiting them, and we do not hold pages back waiting for one. Use this site to understand your situation and to ask better questions of the people treating you.
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