Is Low Potassium a Sign of Cancer?

What Is Potassium?

Potassium is a mineral that helps your muscles contract, keeps your heart rhythm steady, and supports nerve function. When blood levels drop below the normal range, even slightly, it can affect how your body works.

Common reasons for low potassium include

• Not getting enough from food
• Loss through vomiting or diarrhea
• Certain medications such as diuretics
• Kidney problems
• Hormonal imbalances
• Excessive sweating

These are far more common than cancer-related causes, but in some cases cancer can be a factor.

Can Low Potassium Be a Sign of Cancer?

Low potassium is rarely the first sign of cancer, and more often results from unrelated causes. Most people develop it from common causes like diet changes, digestive issues, certain medications, kidney problems, or hormonal imbalances.

In some cases, though, cancer can be behind the drop. This is more likely when the cancer changes hormone levels, affects the digestive system, damages the kidneys, or when treatments cause significant potassium loss.

How Cancer Can Lead to Low Potassium

Cancer may lower potassium through different mechanisms, and some cancer types are more likely to cause these effects:

• Hormone-secreting tumors - Hormone-secreting adrenal or endocrine tumors can produce excess aldosterone or cortisol, which drives potassium loss.
• Digestive tract cancers - Stomach, pancreatic, and intestinal cancers can lead to chronic diarrhea, vomiting, or poor nutrient absorption.
• Kidney cancers - Renal cell carcinoma can impair the kidneys’ ability to filter and balance electrolytes.
• Paraneoplastic syndromes - Certain cancers, including small cell lung cancer, can trigger rare immune or hormonal changes that disrupt potassium regulation.
• Cancer treatments - Chemotherapy, targeted therapies, and corticosteroids may cause potassium loss through fluid changes, kidney strain, or hormonal shifts; this can happen in many cancer types.
• Tumor lysis syndrome - A rare complication in aggressive blood cancers such as certain leukemias and lymphomas, where rapid tumor breakdown disrupts electrolytes.

In most of these situations, low potassium is a complication of the disease or its treatment, not an early warning sign.

How Low Potassium Causes Are Diagnosed in Cancer

To find out why potassium is low, your doctor may:

• Confirm results with a repeat blood test
• Measure potassium loss through urine
• Order imaging to check for tumors or organ changes
• Run hormone panels to assess adrenal or cortisol activity
• Review medications, treatments, and recent illnesses

These steps help determine whether the cause is cancer, a treatment side effect, or something unrelated.

How Is Low Potassium Treated in Cancer?

If cancer or its treatment is responsible, your doctor may:

• Adjust cancer therapies that lower potassium
• Treat or remove hormone-producing tumors
• Correct digestive problems that cause potassium loss
• Recommend dietary changes or supplements under medical supervision
• Monitor potassium levels regularly during treatment

The goal is to restore balance while continuing effective cancer care.