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The Problem With Low Potassium

This essential element acts as an electrolyte and low blood levels can bring fatigue, digestive problems and frequent urination

By Barry Rueger

It was unexpected when my family doctor announced that I had very low potassium levels, or hypokalemia. Aside from prescribing some of the largest pills that I've ever seen, and directing me to an endocrinologist, he had little to say to me. I quickly realized that I knew nothing about this essential element, either inside my body, or in the world around me.

A man getting a blood test to look at potassium levels. Next Avenue, low potassium, hypokalemia
Symptoms of low potassium are quite general, and really a blood test is the only reliable way of measuring potassium levels.  |  Credit: Getty

Potassium, known as its chemical symbol K, is the 17th most common element on Earth, a silvery white metal that you can cut with a knife, but which reacts rapidly with oxygen in the air to form flaky, white potassium peroxide. Potassium is actually incredibly important in farming as potash, and 95% of potassium is used in fertilizers for agriculture. It also has dozens of different uses in things like inks, dyes, wood stains, explosives, fireworks, fly paper and matches.

Roughly 80% of potassium is inside muscle cells, and the rest is in bones, the liver and red blood cells.

I'll admit that I can't recall ever thinking about the potassium in my body. Potassium is one of five "major minerals" found in nearly every part of the body and is one of the most abundant minerals inside humans to help regulate fluids, send nerve signals, and help with muscle contractions. A healthy potassium level is essential to good health. Roughly 80% of potassium is inside muscle cells, and the rest is in bones, the liver and red blood cells.

Inside the water in these cells, potassium acts as an electrolyte, meaning when dissolved in the water inside cells it produces positively charged ions. This allows it to conduct electricity and carry electrical signals to other cells. This messaging is critical to the proper functioning of nerve and muscle cells, particularly heart muscle cells.

What Causes Low Potassium?

Most health authorities agree that getting 3,500 to 4,700 milligrams of potassium daily appears to be the optimal amount, but there is a wide variation in recommendations depending on age, sex and physical attributes. According to the UK National Institute of Health, adult men for instance are said to need 3,400 mg daily, while adult women need only 2,600 mg.

Fortunately potassium is abundant in many whole foods, especially fruits, vegetables and fish. Topping the list for potassium are yams, pinto beans, white potatoes, portobello mushrooms, avocados, sweet potatoes, spinach, kale, salmon, bananas and my favorite: brewed coffee.

Still, experts say that most adults don't meet their daily needs. This is likely due to the Western-style diet, which favors processed foods over whole plant foods that are high in potassium. Fortunately, a lack of potassium in the diet will not usually cause a problem and deficiencies usually happen because the body is losing too much potassium.

Low potassium is often the result of things that cause a person to lose water: diuretic drugs can lead to low potassium, as can intense physical workouts that cause heavy sweating. Heavy drinking can also lead to low potassium.

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Digestive disorders like inflammatory bowel disease can influence fluid and salt balance, which can drop electrolyte levels. Specific conditions such as diabetic ketoacidosis and metabolic alkalosis can also lower potassium levels. Eating disorders, such as anorexia nervosa, purging, or laxative abuse as well as undereating and malnutrition also can lead to lowered potassium levels.

Warning Signs

My diagnosis of low potassium came from a blood test. Symptoms of low potassium are quite general, and really a blood test is the only reliable way of measuring potassium levels. I'm not sure that I had reported any of the common symptoms of low potassium, aside from a general feeling of being tired, and finding myself getting up to pee several times each night, but even if I had, I'm not sure that potassium would have been my doctor's first guess.

Other symptoms include:

General weakness and fatigue: When blood potassium levels are low, the deficiency may affect how the body uses nutrients, and that can result in fatigue. Because the flow of potassium is central to healthy nerve function, low potassium can lead to numbness or tingling in the hands, arms, legs and feet.

Watch for these symptoms, but the truth is that low potassium won't have any obvious symptoms for most people.

Muscle weakness and cramps: When blood potassium levels are low, the brain cannot relay signals to stimulate contractions or to end them. If the brain can't tell muscles to move, people will feel weak.

Irregular heartbeat: The flow of potassium in and out of heart cells helps regulate the heartbeat. Low potassium can lead to an irregular heartbeat or "heart arrhythmia."

Digestive problems: Potassium helps send signals from the brain to the muscles in the digestive system. These "smooth muscles" are what the digestive system uses to churn and propel food through the body so it can be digested. If those muscles don't work properly, it can cause digestive problems like bloating and constipation.

Frequent urination: Just as it may affect the digestive system, low potassium levels may impair the kidneys' ability to concentrate urine and balance the blood's electrolyte levels, leading to increased urination. And excessive urination may lead to even lower levels of potassium.

Watch for these symptoms, but the truth is that low potassium won't have any obvious symptoms for most people.

I was told by my family doctor that I had very low levels of potassium. Instead of the expected 3.6 to 5.2 millimoles of potassium per liter (mmol/L) my blood had only 1.5 mmol/L. That is a level which is considered dangerous.

My doctor ordered a visit with an endocrinologist for more specialized assessment and advice, but because the waiting time would be quite long, I was also prescribed fairly large amounts of potassium chloride — four 1,500 mg tablets each day — to bring my potassium levels back to normal, and weekly blood tests to measure those levels.

Conn's Syndrome

Slowly, but consistently, my potassium levels increased. This was important because I needed to have fairly normal levels of potassium for my endocrinologist to test me for levels of aldosterone, which would indicate whether I was suffering from primary aldosteronism, or Conn's Syndrome.

Aldosterone is a hormone that helps regulate blood pressure by managing the levels of sodium (salt) and potassium in the blood. Having too much or too little aldosterone can cause health issues.

Individuals with Conn's Syndrome have higher-than-normal aldosterone levels. This condition is usually caused by a benign (noncancerous) tumor on one of the adrenal glands, which causes the gland to overproduce aldosterone. High aldosterone levels cause elevated sodium levels and low potassium levels.

The primary test for Conn's Syndrome is the aldosterone to renin ratio (ARR). Aldosterone regulates the levels of sodium and potassium, in part by causing kidneys to excrete potassium through urine. Levels of aldosterone are controlled by renin, an enzyme released by kidneys that triggers the adrenal glands to release aldosterone.

Aldosterone is a hormone that helps regulate blood pressure by managing the levels of sodium (salt) and potassium in the blood.

Laboratories measure the ratio of aldosterone to renin. The test shows the level of each hormone, and the relative balance of aldosterone to renin present in the blood. In healthy individuals, these levels rise and fall together. In those who have primary aldosteronism, aldosterone is high while renin is low — renin is said to be "suppressed." The higher the ARR result, the more likely a person has Conn's syndrome.

Back to the Beginning

After several weeks, my potassium levels had crawled back to the normal range, and I was able to be tested for aldosterone. After another anxious two weeks I was finally told that my aldosterone levels were within normal levels, so I wasn't suffering from Conn's syndrome.

Once my potassium levels are back to normal, they might just stay there.

I passed this test, but the Primary Aldosteronism Foundation warns that, "up to 50% of elevated ARRs may be false-positives. To remediate this risk, patients must undergo confirmatory testing to validate or rule out false positive ARR results."

That places me and my doctors back at the beginning. I'll be pushing for a second set of aldosterone measurements, and I'll be back asking specific questions such as what caused my potassium to be so low? And what is my longer-term outlook?

Happily, if I'm not suffering from Conn's syndrome, the symptoms of hypokalemia might go away after adequate treatment with potassium. Once my potassium levels are back to normal, they might just stay there. And a single instance of hypokalemia doesn't usually cause long-term problems.

It's also possible that if my potassium levels are back to normal, my high blood pressure will improve. A number of studies have found that people who increase their potassium intake see their blood pressure go down.

Barry Rueger
Barry Rueger is a writer with ties to Canada, France, and Appalachia. Barry’s writing focuses on how people live and how their environment influences their choices. With a special focus on development and municipal government, this invariably leads to the discussion of housing and transportation. Barry also writes about technology and dogs, both from an end-user perspective and on a more philosophical level. Follow Barry’s work at https://appalbarry.com. Read More
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