Low Sodium (Hyponatremia) in Skin Cancer: What It Means and When to Worry

Low sodium (hyponatremia) means the level of sodium in your blood is below the typical range and your body’s water balance is disrupted. In people with cancer, hyponatremia is common and can be linked with worse outcomes if not identified and managed promptly. [PM32] Hyponatremia can be mild and subtle or severe and life‑threatening, so it deserves attention and a clear plan with your care team. [PM29]

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Key Takeaways

• Hyponatremia is relatively common during cancer treatment and may come from the cancer itself, treatment side effects, or other medical conditions. [PM32]
• Severe symptoms (nausea, confusion, seizures, fainting) warrant urgent care because rapid drops in sodium can be dangerous. ^[1]
• Several treatable causes exist, including medication effects (e.g., chemotherapy), immune‑therapy related hormone issues, and dehydration or excess fluids. Addressing the cause typically improves sodium levels. [PM32]

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Why Skin Cancer Patients Can Develop Low Sodium

Treatment‑related effects

• Some chemotherapy regimens and supportive drugs can shift fluid and hormone balance, contributing to hyponatremia. Electrolyte disorders, including hyponatremia, occur frequently during anti‑tumor therapy and hospitalization. [PM30]
• Immune checkpoint inhibitors (ICIs) used in melanoma, squamous cell skin cancer, and Merkel cell carcinoma can trigger endocrine problems (hormone gland inflammation or failure), which may present with hyponatremia. When serious neurologic or metabolic signs emerge (lethargy, seizures, hyponatremia), clinicians typically pause ICIs, evaluate for infection, and treat urgently with steroids under endocrinology guidance. ^[2]

Endocrine (hormone) causes

• Adrenal insufficiency (low adrenal hormone output) related to immunotherapy can result in hyponatremia and requires prompt evaluation and steroid replacement. ^{[3] [2]}
• Thyroid problems are also common with ICIs; while thyroid dysfunction itself doesn’t always cause hyponatremia, it can contribute to fatigue and fluid balance issues that complicate sodium management. ^[4]

Other cancer and medical factors

• Syndrome of inappropriate antidiuretic hormone (SIADH) causes water retention and dilutes sodium; it’s a known cancer‑associated mechanism of hyponatremia across malignancies. [PM32]
• Kidney dysfunction, low albumin, surgery/chemotherapy exposure, and comorbidities increase risk of electrolyte disorders and worse hospital outcomes. [PM30]

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How Serious Is It?

Hyponatremia ranges from mild to severe:

• Mild or chronic hyponatremia may cause subtle symptoms like headache, low energy, or muscle cramps and still warrants evaluation because chronic low sodium is associated with falls and cognitive issues. ^[5]
• Severe or rapidly dropping sodium can cause nausea, confusion, seizures, and coma; this is a medical emergency and needs immediate treatment. Seek emergency care if severe symptoms occur. ^[1]
• In cancer populations, electrolyte disturbances, including hyponatremia, correlate with higher in‑hospital mortality, longer stays, and higher costs, underscoring the importance of prevention and early correction. [PM30]
• Overall, cancer‑associated hyponatremia is tied to worse morbidity and mortality, but timely diagnosis and targeted therapy improve outcomes. [PM29] [PM32]

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Common Symptoms to Watch For

• Nausea or vomiting
• Headache
• Confusion or trouble thinking clearly
• Fatigue or drowsiness
• Irritability or restlessness
• Muscle weakness, cramps, or spasms
• Seizures or loss of consciousness

If you or a loved one develops severe symptoms like confusion, seizures, or fainting, seek emergency care immediately. ^{[1] [6]}

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What Your Care Team Will Usually Check

• Blood tests: Sodium, potassium, creatinine (kidney function), glucose, thyroid function, cortisol (for adrenal function), and osmolality to differentiate causes. In ICI‑treated patients, urgent endocrine evaluation is recommended when hyponatremia appears with neurologic symptoms. ^[2]
• Urine tests: Sodium and osmolality to assess SIADH versus dehydration. [PM32]
• Medication review: Chemotherapy, immunotherapy, diuretics, antidepressants, anti‑seizure drugs, and pain medications can influence sodium. [PM32]
• Fluid balance assessment: Intake, losses, and signs of dehydration or fluid overload. [PM32]

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How Hyponatremia Is Treated

Treatment depends on the cause and severity:

• Severe, symptomatic cases: Hospital management with controlled correction using IV saline or hypertonic saline, careful monitoring to avoid overly rapid correction, and addressing the underlying trigger. Urgent steroid therapy is often used if adrenal insufficiency is suspected during immunotherapy. ^[2]
• SIADH: Fluid restriction, salt tablets, loop diuretics, or vasopressin antagonists in select situations; and treating the underlying driver (e.g., medication adjustment). [PM32]
• Endocrine causes: Replace deficient hormones (e.g., hydrocortisone for adrenal insufficiency), which often normalizes sodium. ^[2]
• Medication‑related: Adjust or pause the offending agent if clinically appropriate, with oncologist guidance. [PM32]
• Supportive care: Correct concurrent low potassium, magnesium, or calcium; optimize nutrition and albumin; monitor closely during chemotherapy cycles. [PM30]

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Special Considerations for Immunotherapy

• ICIs can cause immune‑related adverse events (irAEs) affecting glands like the adrenal and thyroid, and hyponatremia can be a sign of these. Prompt work‑up and coordinated care with endocrinology are standard when neurological or metabolic symptoms coincide with hyponatremia. ^[2]
• Product safety information for nivolumab lists hyponatremia among laboratory abnormalities observed during treatment, highlighting the need for routine monitoring. ^[7]

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Practical Tips You Can Use

• Know the signs: If you feel unusually nauseated, confused, profoundly tired, or have muscle cramps, let your team know quickly. Severe symptoms require emergency evaluation. ^[1]
• Bring a medication list: Include all prescriptions and supplements; some can lower sodium. [PM32]
• Discuss fluid intake: Excess water when the body is retaining water (e.g., SIADH) can worsen hyponatremia; your team can guide safe limits. [PM32]
• Ask about endocrine testing if you’re on immune therapy and develop unexplained fatigue, dizziness, or low sodium; early detection helps. Urgent steroid treatment is common when adrenal insufficiency is suspected. ^[2]
• Keep routine labs: Regular electrolyte checks during and after treatment help catch issues early and avoid complications. Monitoring reduces risks tied to electrolyte disorders in cancer care. [PM30]

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Bottom Line

Low sodium in the context of skin cancer is not uncommon and often treatable. It can signal issues such as SIADH, treatment side effects, or immune‑therapy‑related hormone problems, and addressing the root cause typically improves sodium and symptoms. [PM32] Because severe hyponatremia can be dangerous, recognizing symptoms and getting prompt evaluation is important for safety and better outcomes. ^[1] [PM29]

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