Low potassium, or potassium deficiency, is when your blood potassium level is below 3.5 mmol per liter. In the medical community, it’s known as hypokalemia.
Potassium is an essential mineral that has many roles in your body. For example, it helps regulate muscle contractions, maintain healthy nerve function, and regulate fluid balance.
Despite its importance, it’s estimated 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 — such as fruits, vegetables, beans, and nuts.
Still, hypokalemia is rarely caused by dietary deficiency alone. It can be caused by several factors, including:
- fluid loss
- use of certain medications
- some medical conditions, like kidney failure
Keep reading to learn more about potassium deficiency, including its causes and symptoms.
Causes of potassium deficiency
While it’s generally rare to develop potassium deficiency, certain illnesses or other factors can cause it, including:
- Chronic diarrhea. This can be caused by the overuse of diuretics or laxatives, irritable bowel disease, or infections.
- Certain medications. These may include beta 2-agonists, theophylline, insulin, diuretics, corticosteroids, and antimicrobials.
- Eating disorders. These include anorexia nervosa, purging, or laxative abuse.
- Under eating or malnutrition
- Cushing’s syndrome
- Hyperaldosteronism. This condition is characterized by excess aldosterone, a steroid hormone, in the blood.
- Kidney failure
- Kidney disorders. These include Bartter syndrome, Gitelman syndrome, and Fanconi syndrome.
- Hypomagnesemia. This is also called low magnesium levels.
- Refeeding syndrome
- Overconsumption of licorice
- Excessive sweating
If you’re taking certain medications for kidney disease, such as diuretics, and you suspect your potassium is low, speak with a healthcare professional. They can review your blood tests and adjust your medications or diet as needed.
If you’ve experienced chronic fluid loss or have misused any medications, seek immediate medical attention.
Symptoms of potassium deficiency
Here are eight signs and symptoms of potassium deficiency.
Weakness and fatigue
Weakness and fatigue are often the first signs of potassium deficiency, for a few reasons.
First, potassium helps regulate muscle contractions. When blood potassium levels are low, your muscles produce weaker contractions.
Second, deficiency in this mineral may affect how your body uses nutrients in a way that can result in fatigue.
For example, some evidence shows that a deficiency could impair insulin production. This can result in high blood sugar levels and less available glucose, which functions as energy for your cells.
Summary: Since potassium helps regulate muscle contractions, deficiency may result in weaker contractions. A deficiency may impair your body’s handling of nutrients, like sugar, which can lead to fatigue.
Muscle weakness and cramps
Muscle cramps are sudden, uncontrolled contractions of the muscles. They can occur when blood potassium levels are low and can be painful.
Within skeletal muscle, potassium helps relay signals from your brain to stimulate contractions. It also helps end these contractions by leaving the muscle cells. When blood potassium levels are low, your brain cannot relay these signals as effectively.
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This results in more prolonged contractions and is thought to contribute to muscle cramps. Cramps are unlikely to occur with mild or moderate hypokalemia, but they may happen with severe hypokalemia of less than 2.5 mmol/L of potassium.
In rare cases, severe hypokalemia can also cause rhabdomyolysis. This is a dangerous medical condition involving the breakdown of muscle tissue that releases a damaging protein into the blood, potentially leading to organ damage.
In most cases, significant muscle weakness occurs with severe hypokalemia, though it can sometimes occur with acute onset of mild or moderate hypokalemia as well.
Summary: Potassium helps start and stop muscle contractions. Low blood potassium levels can affect this balance, causing uncontrolled and prolonged contractions known as cramps.
While digestive problems have many causes, they may occur with severe hypokalemia.
Potassium helps relay signals from your brain to muscles located in the digestive system known as smooth muscle. These signals stimulate contractions that help your digestive system churn and propel food, so it can be digested.
With low potassium levels, contractions in the digestive system may become weaker and slow the movement of food. This could cause digestive problems, like bloating and constipation.
In particular, constipation is most associated with severe hypokalemia.
Summary: Potassium deficiency may cause issues like bloating and constipation because it can slow the movement of food through the digestive system.
Potassium also plays a vital role in maintaining healthy heart muscle contractions.
This is because the flow of potassium in and out of heart cells helps regulate your heartbeat. Low blood potassium levels can alter this flow, resulting in abnormal heart rhythms known as heart arrhythmia.
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Heart arrhythmias can also be a sign of a serious heart condition. If you notice any abnormal changes in your heart rate, seek immediate medical attention.
Summary: Potassium plays a key role in regulating your heart rate. If levels are too low, it may lead to an irregular heartbeat known as heart arrhythmia, which can be a sign of a serious heart condition.
A severe potassium deficiency can cause breathing difficulties.
Breathing requires multiple muscles, especially your diaphragm, to help the lungs inhale and exhale air.
When blood potassium levels are severely low, your lungs may not expand and contract properly, resulting in shortness of breath.
Severe potassium deficiency may even stop the lungs from working, which is fatal.
One study found that people with low or high blood potassium levels — called hypokalemia and hyperkalemia, respectively — were at significantly higher risk of in-hospital respiratory failure and the need for a ventilator compared with people with healthy potassium levels.
Summary: Potassium helps the lungs expand and contract, so potassium deficiency may result in shortness of breath.
Tingling and numbness
Though more common in people with high potassium, or hyperkalemia, those with potassium deficiency may also experience persistent tingles and numbness.
This is known as paresthesia and usually occurs in the hands, arms, legs, and feet.
Potassium is important for healthy nerve function. Low blood levels can weaken nerve signals and result in tingling and numbness.
While occasionally experiencing these symptoms is harmless — like if your foot falls asleep from lack of movement or sitting in an awkward position — persistent tingles and numbness may be a sign of an underlying condition.
If you experience this, it’s best to contact a doctor.
Summary: Persistent tingling and numbness may be a sign of impaired nerve function due to potassium deficiency. If you experience this, it’s best to contact a healthcare professional.
Polyuria (frequent urination)
Polyuria is a condition where you pee more than usual.
The kidneys are responsible for balancing your body’s fluid and electrolyte levels and removing any waste through the urine.
Low potassium levels may impair your kidneys’ ability to concentrate urine and balance the blood’s electrolyte levels, leading to increased urination. You may also notice increased thirst, known as polydipsia.
Excessive urination may lead to lower levels of potassium. Therefore, it’s important to speak with a healthcare professional if you notice a sudden change in how often you urinate.
Summary: In some cases, low potassium may impair your kidney’s ability to regulate your body’s fluid and electrolyte balance. As such, you may feel the need to urinate more often.
High blood pressure
Having the perfect balance of electrolytes is important for maintaining healthy blood pressure.
You may be aware that consuming too much sodium can increase blood pressure in some people. Yet, few people know that too little potassium in the diet can have the same effect.
Potassium helps your kidneys get rid of excess sodium via urine. If there isn’t enough potassium in the blood, the kidneys reabsorb sodium back into the bloodstream, potentially leading to high blood pressure over time.
This most often occurs with a low dietary intake of potassium — and specifically with hypokalemia.
Therefore, getting enough potassium in your diet may be a way to maintain healthy blood pressure in some individuals.
If you have high blood pressure, it’s best to talk with a healthcare professional about monitoring and treatment.
Summary: Potassium plays a key role in regulating sodium levels in your body. When your potassium levels are low, your kidneys retain more sodium in the body, which can lead to increased blood pressure.
How to treat hypokalemia
In most cases, hypokalemia will need to be treated by a healthcare professional.
Mild to moderate hypokalemia is typically treated with oral potassium supplements. In some cases, your healthcare professional may also need to adjust any other medications or treat underlying causes, like diarrhea, vomiting, or eating disorders.
A potassium-rich diet is usually not enough to treat hypokalemia, since most potassium in food is paired with phosphate, not potassium chloride. Hypokalemia often also involves a chloride deficiency, so it’s best to treat both deficiencies with potassium chloride supplements.
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Usually, 60–80 mmol of supplements per day for a few days to weeks is sufficient for treating mild to moderate hypokalemia. That said, always follow the recommendations of your healthcare professional.
In severe hypokalemia cases, intravenous (IV) treatment may be recommended. This should be strictly monitored by a healthcare professional due to the high risk of rebound hyperkalemia, or high potassium, which can be fatal.
Summary: Hypokalemia usually requires oral supplementation or IV therapy to restore levels. While eating a potassium-rich diet is encouraged, it often will not restore your potassium levels on its own.
Should you take potassium supplements?
Unless otherwise advised by a healthcare professional, self-treatment of hypokalemia with over-the-counter (OTC) potassium supplements is not recommended.
Mild to moderate hypokalemia is often treated with potassium chloride supplements, usually ranging from 60–80 mmol per day. This dosage can often replenish potassium levels without the risk of rebound hyperkalemia.
However, potassium supplements may irritate the lining of the bowel, leading to bleeding or ulceration. Therefore, they should be taken with food and water.
In the United States, most OTC potassium-only supplements are limited to 99 mg, largely due to concerns of bowel irritation. The Food and Drug Administration (FDA) also requires that certain potassium salts are labeled with a warning about bowel lesions.
Taking too much potassium can cause excess amounts of the mineral to build up in the blood, a condition known as hyperkalemia. Hyperkalemia may cause heart arrhythmia or other serious heart conditions that can be fatal.
Unless they’re prescribed by your healthcare professional, and you’re being closely monitored, avoid taking potassium-only supplements.
Summary: It’s not recommended to take OTC potassium supplements unless advised and monitored by a healthcare professional.
Sources of potassium
Though diet alone usually will not resolve hypokalemia, it’s still beneficial to increase your intake of potassium-rich foods, like fruits, vegetables, beans, and nuts.
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In 2019, the National Academies of Sciences, Engineering, and Medicine (NASEM) updated the reference daily intakes for potassium, concluding that insufficient data support the previous recommendation of 4,700 mg of potassium per day for adults.
As such, they developed adequate intakes (AI) based on age and sex. Currently, the AI for potassium is 2,600 mg and 3,400 mg per day for women and men, respectively.
Regardless, because only 85–90% of potassium is absorbed from food, the percent of the daily value listed on food labels remains at 4,700 mg. Keep this in mind to help you ensure you’re getting enough.
Here’s a list of foods that are excellent sources of potassium:
- Dried apricots: 1/2 cup (190 grams) contains 1,100 mg (23% of the daily value)
- Cooked lentils: 1 cup (198 grams) contains 731 mg (16% of the daily value)
- Cooked acorn squash: 1 cup (205 grams) contains 644 mg (14% of the daily value)
- Cooked potato: 1 medium (167 grams) contains 610 mg (13% of the daily value)
- Canned kidney beans: 1 cup (260 grams) contains 607 mg (13% of the daily value)
- Orange juice: 1 cup (236 mL) contains 496 mg (11% of the daily value)
- Banana: 1 medium (115 grams) contains 422 mg (9% of the daily value)
- Sirloin beef steak: 1 ounce (85 grams) contains 315 mg (7% of the daily value)
- Milk (1% fat): 1 cup (236 mL) contains 366 mg (8% of the daily value)
- Natural Greek yogurt: 3/4 cup (214 grams) contains 240 mg (5% of the daily value)
- Tomato: 1 medium (123 grams) contains 292 mg (6% of the daily value)
- Brewed coffee: 1 cup (235 mL) contains 116 mg (2% of the daily value)
While increasing your potassium intake won’t likely raise your low potassium levels, eating a potassium-rich diet is still beneficial to your health.
Summary: Potassium is found in a variety of whole foods, especially fruits, vegetables, beans, lentils, and dairy products. Currently, the AI for potassium is 3,400 mg for men and 2,600 mg for women.
Few people meet the daily recommended potassium intake, which is 3,400 mg for men and 2,600 mg for women.
Nevertheless, hypokalemia is rarely caused by dietary deficiency alone. It can be caused by several factors, including fluid loss, malnutrition, shock, using certain medications, and medical conditions like kidney failure.
Common signs and symptoms of potassium deficiency include weakness and fatigue, muscle cramps, muscle aches and stiffness, tingles and numbness, heart palpitations, breathing difficulties, digestive symptoms, and changes in blood pressure.
If you think you’re deficient, contact a healthcare professional. Potassium deficiency can have serious health consequences.
If you notice any sudden changes in your breathing or heartbeat, seek immediate medical attention.
Quick tip: Aim to have 2–3 potassium-rich foods each day. For example, a banana for breakfast, 1/2 cup (130 grams) of kidney beans at lunch, and white potatoes on your dinner plate.