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Potassium Blood Test: Causes of Low & High Levels + Ways to Improve

Written by Biljana Novkovic, PhD | Last updated:
Puya Yazdi
Medically reviewed by
Puya Yazdi, MD | Written by Biljana Novkovic, PhD | Last updated:

Potassium is an electrolyte that is key to nerve and muscle function, blood pressure, and fluid balance. Abnormal levels can be a sign of underlying health issues. Learn about the causes and effects of low and high potassium levels. and what you can do to improve them.

What is Potassium?

Potassium in The Human Body

Potassium is an essential mineral and positive ion that has many important functions in our bodies.

Potassium [1, 2, 3]:

  • controls blood pressure
  • helps balance fluids
  • is needed for nerves and muscles to communicate
  • helps store nutrients, including glucose, inside of cells

The majority of the body’s potassium is located inside the cells, where it is involved in the production of proteins, helps maintain water balance, plays a role in cell division and accelerates chemical reactions [4, 5].

The largest storage of potassium in the human body is in the muscles [1].

The blood levels of potassium, called serum potassium in medical literature, amount to only about 2% of the total body potassium [1].

Potassium is absorbed through the gut and removed by the kidneys through urine [1, 6].

Testing potassium is important for evaluating kidney, heart, and adrenal health.

Normal Range

The normal range is around 3.5- 5.3 mmol/L. It can vary slightly between laboratories.

Even minor departures from the normal range are associated with significant negative effects [7].

Several factors contribute to variations in serum potassium levels. A study showed that serum potassium was lowest in the evening (around 9 p.m.) and highest in the early afternoon (1 – 3 p.m.) [8].

Average ranges of serum potassium can vary for people in different geographic locations, likely as a result of dietary differences [9]. One study has found that men in China have lower serum potassium levels than averages in other parts of the world [9].

In the United States, serum potassium concentrations tend to be lower in African Americans than in people of European ancestry [10].

During pregnancy, it is normal that potassium levels are higher because the kidneys eliminate less potassium; increases in the hormone progesterone could be responsible for adapting the body to this change.

Low Potassium Levels

Low potassium is known as “hypokalemia” (hypo = low, kalemia = blood potassium).

A result that’s lower than normal, doesn’t necessarily mean that you have a health condition needing treatment. Your doctor will interpret your result, taking into account your medical history, symptoms, and other test results.


Causes shown below are commonly associated with low potassium levels. Work with your doctor or another health care professional to get an accurate diagnosis.

Factors that can decrease potassium include:

  • Dehydration due to diarrhea or vomiting [11, 12]
  • Low potassium intake, especially when combined with a diet high in sodium [11, 13]
  • Alcoholism [14]
  • Magnesium deficiency [15, 11]
  • Chronic stress or anxiety [16, 17]
  • Excess of adrenal hormones (e.g. Conn syndrome, Cushing’s syndrome) [18]
  • Kidney problems [19, 11, 12]
  • Licorice, in excess [20, 21]
  • Barium poisoning [22, 23]
  • Rare genetic disorders [11]

Serum potassium in healthy people does not vary significantly with dietary potassium or the amount of potassium stored in the body [3].

As a result, poor potassium intake is often not the true cause of hypokalemia. However, people with extremely poor diets and people on severe weight-reduction programs are in danger of developing severe potassium deficiency [24, 25, 7, 26].

Some drugs can also decrease potassium levels, including:

  • Water pills (diuretics) [11, 27]
  • Laxatives [11]
  • Insulin [11, 27, 1]
  • Glucocorticoid, often used to suppress allergic, inflammatory, and autoimmune disorders [28]
  • Penicillin [11, 27]
  • Acetaminophen (Tylenol, Panadol, paracetamol) overdose [29, 30]


Symptoms of low potassium include [11, 27, 31]:

  • Weakness
  • Fatigue
  • Muscle cramps
  • Constipation
  • Irregular heartbeat

Why is Low Serum Potassium Bad?

Low serum potassium (hypokalemia) can cause severe disturbances in heart, brain, and muscle function [32].

Increasing Potassium

The most important thing is to work with your doctor to find out what’s causing your low potassium and to treat any underlying conditions!

Discuss the additional strategies listed below with your doctor. None of these strategies should ever be done in place of what your doctor recommends or prescribes!

To make sure you have enough potassium:

  • Eat more potassium-rich foods such as fresh fruits and fresh vegetables. These have higher amounts of potassium than cereals and meat [1]. Good sources include bananas, raisins, prunes, apricots, dates, dairy, strawberries, citrus, watermelon, soy, pumpkin, nuts, and beets.
  • Decrease your salt (sodium chloride) intake. Salting foods and discarding the liquid leads to a sodium for potassium exchange that reduces the potassium content of the food [1]. Also avoid foods high in sodium like pre-packaged foods, fast foods, smoked and pickled foods, canned meats, lunch meats, and chips.
  • Discuss using salt substitutes that contain potassium with your doctor [13]. These shouldn’t be used if you have a medical condition such as diabetes, heart, or kidney disease, or if they interfere with your medications.
  • Reduce your coffee/caffeine intake. Caffeine decreases blood potassium [33, 34].
  • Check your magnesium. Make sure you are not magnesium deficient. Magnesium deficiency can further lower potassium levels [15, 35, 11]

Studies have found that anxiety increases adrenal hormones, which can decrease blood potassium [17]. Avoid or manage stress. Good strategies to manage stress are getting adequate rest, engaging in exercise, relaxation, meditation, etc.

Discuss supplemental potassium with your doctor. This supplement should always be provided under medical supervision due to potential toxicity, especially if you have kidney disease [36, 37].

High Potassium Levels

High potassium is called “hyperkalemia” (hyper = high, kalemia = blood potassium).

In most people, high potassium can be eliminated or stored away. But in people with certain disorders or diseases, the elimination and storage do not function properly. Also, some drugs can increase potassium above normal.

However, a result that’s higher than normal, doesn’t necessarily mean that you have a health condition needing treatment. The result can vary depending on the way your blood sample was taken, for example. Your doctor will interpret your result, taking into account your medical history, symptoms, and other test results.


Causes shown below are commonly associated with high potassium levels. Work with your doctor or another health care professional to get an accurate diagnosis.

High potassium can be caused by:

  • Kidney disease [38, 39]
  • Dehydration [38]
  • Tissue injury and damage [38]
  • Infection [38]
  • Adrenal insufficiency (e.g. Addison’s disease) [40, 41]
  • Type 1 diabetes [40]
  • Excessive intake of potassium-rich fruits or juices or excessive use of supplements (almost never without other underlying issues) [40]
  • Some rare genetic disorders [38]

The following drugs can increase potassium levels:

  • Non-steroidal anti-inflammatory drugs (NSAIDs), such as ibuprofen [42]
  • Medications that reduce blood pressure, such as beta-blockers, ACE inhibitors, and angiotensin receptor blockers [43, 44, 45]
  • Potassium-sparing diuretics [39]
  • Proton pump inhibitors that reduce stomach acid production, such as omeprazole [46]


High potassium levels are often without symptoms. Alternatively, a person can experience [40, 47]:

  • Weakness
  • Pounding or racing heartbeat
  • Numbness of the extremities
  • Muscle pain
  • Labored breathing
  • Nausea

Why is High Serum Potassium Bad?

Left unaddressed, moderate to severely elevated serum potassium (hyperkalemia) can lead disturb the heart rhythm, which can be fatal [40]. Extremely high serum potassium should thus be handled as an emergency, and monitoring levels of those at risk is essential [40].

Older patients, patients with chronic heart failure, kidney failure, and diabetic patients are prone to developing hyperkalemia [48].

Decreasing Potassium

The most important thing is to work with your doctor to find out what’s causing your high potassium and to treat any underlying conditions.

Make sure you are well hydrated [38]. Dehydration can increase blood potassium.

Avoid salt substitutes and packaged foods that contain them, as they usually contain potassium. If your kidney function is impaired, you may need to go on a low potassium diet.

About the Author

Biljana Novkovic

Biljana Novkovic

Biljana received her PhD from Hokkaido University.
Before joining SelfHacked, she was a research scientist with extensive field and laboratory experience. She spent 4 years reviewing the scientific literature on supplements, lab tests and other areas of health sciences. She is passionate about releasing the most accurate science and health information available on topics, and she's meticulous when writing and reviewing articles to make sure the science is sound. She believes that SelfHacked has the best science that is also layperson-friendly on the web.


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