Low potassium is not usually a sign of cancer. It more often happens in people who already have cancer due to vomiting, diarrhea, poor intake, or side effects from medicines that affect the kidneys. In rare cases, certain tumors (like small cell lung cancer) can cause hormone changes that make potassium drop and stay low despite supplements. Learn more about what can cause low and high potassium and the symptoms this can present with.
Most low potassium in cancer care is linked to fluid losses, diuretics, or chemotherapy that irritates the kidneys. Keeping up with fluids and reporting nausea, vomiting, or diarrhea early helps prevent drops in potassium and other salts.
If low potassium keeps coming back or is hard to correct, the doctor may look for less common causes, such as hormone problems that raise aldosterone. These conditions make the kidneys waste potassium and need specific treatment.
Anyone with unexplained or persistent low potassium should see a family doctor or oncologist for proper testing and treatment. Avoid self-medicating with potassium without medical advice, as too much can affect the heart. A simple prevention tip is to stay hydrated and seek care promptly if vomiting or diarrhea lasts more than 24 hours.