Receiving a blood test result indicating low potassium can be alarming. It is easy to feel confused when your doctor flags a nutrient deficiency you likely never thought about before. Naturally, you want answers immediately. Unfortunately, a quick online search yields terrifying results. You might see articles associating our symptoms with rare tumors or other severe conditions. While these possibilities exist, they are actually relatively uncommon compared to different explanations.

In reality, most cases are caused by simpler issues like medication side effects or chronic dehydration from illness. Understanding these common triggers helps you avoid unnecessary panic and focus on the practical steps needed for your recovery. Low potassium is usually not a sign of cancer. It is very common and is usually caused by simple things like dehydration, medicines or stomach bugs, according to the Cleveland Clinic. While some rare cancers can affect levels, it is not the first thing medical professionals look for.

What’s happening in your body

Potassium is a mineral that acts like an electric messenger for your body. It helps your muscles move, your nerves send signals and your heart beat steadily, as defined by Mayo Clinic. When you do not have enough of this vital mineral, it is referred to as hypokalemia.

Imagine a car running out of oil. Without sufficient potassium, your body’s engine starts to sputter. You might feel weak, fatigued or have muscle cramps. If it gets really low, it can be dangerous for your heart, as noted by Healthline.

Common causes of low potassium

Most of the time, low potassium has nothing to do with cancer. It usually happens because you are losing fluids too quickly, according to the National Kidney Foundation.

Specific causes

One of the most common reasons is stomach illness, as noted by the World Health Organization. This is because if you have been vomiting or experiencing diarrhea, your body loses a significant amount of potassium. Sweating is another cause, as working out very hard or working in the heat can cause you to lose minerals. A poor diet can also contribute, specifically from not eating enough fruits and vegetables, though this is rare as the only cause.

Medicines are actually the most common reason, as certain pills make you pee more, which flushes potassium out. In fact, a 2015 study found that medications cause hypokalemia through several mechanisms, including intracellular shifting and increased renal loss.

Diagnosis and treatment

The only way to know for sure if you have low potassium is through a simple blood test, which medical professionals typically check during a yearly physical or if you experience symptoms such as weakness. Fixing this condition depends on how low your levels are. For mild cases, your healthcare expert might recommend eating more foods like bananas, potatoes or spinach, according to Healthline. In less severe cases, you might take a supplement.

Specific diagnosis/treatment

If your levels are severe and potentially life-threatening, you may need to go to the hospital to receive treatment through a small tube in your arm, called an intravenous (IV) line. “Of all the various signs related to cancer, low potassium would not be on top of the list,” said S. Adam Ramin, MD, board-certified urologist, urologic oncologist and medical director of Urology Cancer Specialists in Los Angeles, California.

What drains potassium from the body?

Your kidneys are responsible for regulating levels and act as filters for the body. If your kidneys decide to dump potassium into your urine, your blood levels drop. Several factors signal your kidneys to excrete potassium. Diuretics, also known as water pills according to the Mayo Clinic, used to lower blood pressure, are a significant cause.

Hopkins Medicine notes that a hormone called aldosterone controls salt and water, and if you have too much of it, you lose potassium. Additionally, if you are low in magnesium, your kidneys may struggle to retain effectively, per the Cleveland Clinic.

What cancers can cause low potassium levels?

While it is rare, some cancers can mess with your hormones, which then messes with your potassium. The Mayo Clinic explains that adrenal cancer can affect the adrenal glands that sit on top of your kidneys. If a tumor grows there, it can make too much of the hormone aldosterone, which forces your kidneys to pee out all your potassium in a condition called Conn’s Syndrome.

Studies note that, sometimes, certain lung tumors produce a hormone called ACTH that tells your body to make steroids, which lowers potassium. Leukemia can sometimes cause an abnormally high number of white blood cells, which can confuse the blood test machine, making it appear as if levels are abnormal even when the body is healthy. It is also important to note that often it is not the cancer itself causing low potassium, but the chemotherapy drugs used to treat it.

What drugs can cause low potassium levels?

“Actually, many common medicines in your bathroom cabinet can lower your potassium levels,” explains Dr. Justus Rabach, MD, Clinical Medicine and Surgery (MBChB). “For example, my first direction would be diuretics, or ‘water pills’ like Hydrochlorothiazide. It is used to treat high blood pressure, which is a frequent cause. Additionally, using laxatives too often flushes out nutrients, while steroids like prednisone for inflammation can also deplete your levels.”

Other strong treatments can also disrupt your balance. Certain antibiotics, such as penicillin or gentamicin, can affect how your kidneys filter potassium. The Clinical Kidney Journal notes that insulin used to treat diabetes actively moves it out of the bloodstream and into cells, resulting in lower levels on tests.

When to see a doctor

You should see a doctor if you have symptoms that do not go away, especially if you take water pills. You should go to the emergency room if you feel like your heart is skipping beats or fluttering. Other serious warning signs include severe muscle weakness where you feel like you cannot lift your arms, trouble breathing, confusion and extreme dizziness.

Bottom line

Low levels are usually a sign of dehydration, certain medications, or inadequate intake of nutrient-dense foods. While very specific, rare cancers can cause it by changing your hormones, low potassium alone is rarely the first sign of cancer. If your levels are low, your doctor will likely examine your medications and diet before considering anything more serious.

Frequently Asked Questions

What is the number one cause of low potassium?

The most common cause is the use of diuretics or water pills prescribed for high blood pressure or heart failure.

What’s the best way for your body to absorb potassium?

Whole foods, such as fruits and vegetables, are a better and safer option than taking pills, as your body absorbs them more slowly and naturally.

How does alcohol affect potassium levels?

Alcohol causes you to urinate more often, which can quickly flush potassium and magnesium out of your body and lead to low levels.

Citations

Cleveland Clinic. Hypokalemia. Cleveland Clinic. Published May 10, 2022. https://my.clevelandclinic.org/health/diseases/17740-low-potassium-levels-in-your-blood-hypokalemia

Mayo Clinic Staff. Low potassium (hypokalemia). Mayo Clinic. Published 2018. https://www.mayoclinic.org/symptoms/low-potassium/basics/definition/sym-20050632

Raman R. 8 Signs and Symptoms of Potassium Deficiency (Hypokalemia). Healthline. Published March 7, 2018. https://www.healthline.com/nutrition/potassium-deficiency-symptoms

National Kidney Foundation. Potassium. National Kidney Foundation. Published 2024. https://www.kidney.org/kidney-topics/potassium

WHO. Diarrhoeal Disease. Who.int. Published March 7, 2024. https://www.who.int/news-room/fact-sheets/detail/diarrhoeal-disease

Veltri KT, Mason C. Medication-Induced Hypokalemia. Pharmacy and Therapeutics. 2015;40(3):185. https://pmc.ncbi.nlm.nih.gov/articles/PMC4357351/

O’Brien S. 15 Foods That Pack More Potassium Than a Banana. Healthline. Published July 26, 2018. https://www.healthline.com/nutrition/foods-loaded-with-potassium

Mayo Clinic. Do diuretics cause low potassium? Mayo Clinic. Published 2019. https://www.mayoclinic.org/diseases-conditions/high-blood-pressure/expert-answers/blood-pressure/faq-20058432

Hamrahian A, Morris-Wiseman L. Primary Aldosteronism. www.hopkinsmedicine.org. Published September 21, 2022. https://www.hopkinsmedicine.org/health/conditions-and-diseases/primary-aldosteronism

Cleveland Clinic. Hypomagnesemia: What It Is, Causes, Symptoms & Treatment. Cleveland Clinic. Published June 14, 2022. https://my.clevelandclinic.org/health/diseases/23264-hypomagnesemia

Mayo Clinic. Adrenal cancer – Symptoms and causes. Mayo Clinic. Published 2019. https://www.mayoclinic.org/diseases-conditions/adrenal-cancer/symptoms-causes/syc-20351026

Li T, Vijayan A. Insulin for the treatment of hyperkalemia: a double-edged sword? Clinical Kidney Journal. 2014;7(3):239-241. doi:https://doi.org/10.1093/ckj/sfu049