Are Your Potassium Levels Low? What to Know About Hypokalemia

Potassium is a critical electrolyte in your body. It provides electricity to your cells. It also helps maintain the acid-base balance in your body. This makes it necessary for many bodily functions, from contracting your muscles to helping your heart pump blood. 

If your potassium levels get too low, problems can arise. In many cases, it doesn’t cause any symptoms. People usually find out they have hypokalemia after a routine blood test. In other cases, though, it can make people very sick and be life threatening. 

What is hypokalemia?

Hypokalemia is the medical term for a low potassium level in the blood. Normal blood potassium levels are 3.5 mEq/L to 5.0 mEq/L. Hypokalemia is when the amount of potassium in the blood falls below 3.5 mEq/L. It can be categorized as:

• Mild: 3.0 mEq/L to 3.5 mEq/L

• Moderate: 2.0 mEq/L to 2.9 mEq/L

• Severe: less than 2.0 mEq/L

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Hypokalemia is diagnosed with a routine blood test. The test measures several different electrolytes in your blood, along with your kidney function. 

Mild hypokalemia is quite common. It is found in up to 14% of routine outpatient lab tests. 

But more severe cases of hypokalemia are possible, too. These cases tend to occur in someone who is sick for other reasons. If your levels of potassium are very low, this can start to affect your heartbeat (more on complications later). 

EXPERT PICKS: WHAT TO READ NEXT

• Explore supplements: Browse the types of supplements available to prevent and treat hypokalemia. 

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What causes hypokalemia?

There are many causes of low potassium levels. It may be surprising to learn that the problem is not usually from eating less foods with potassium. Most Americans get enough potassium from their diet. More often, the causes of hyperkalemia are related to the kidneys or GI (gastrointestinal) tract. 

Kidney causes of hypokalemia

The potassium level in your body is mainly controlled by your kidneys. When potassium levels get too high, they pull the excess potassium from the blood into your urine so that you pee it out. When your potassium drops too low, the kidneys keep the potassium in the blood rather than putting any in the urine. 

The following conditions can disrupt how your kidneys regulate potassium, leading to hypokalemia:

• Uncontrolled diabetes: When someone’s blood sugar level is high, the kidneys try to lower it by transferring the excess sugar into the urine. In order to do this, they also have to pull extra potassium into the urine.

• Low magnesium levels: The kidneys regulate both potassium and magnesium levels in the blood. When someone has low magnesium, the kidneys work to preserve magnesium levels in the body. Unfortunately, this can cause the kidneys to put more potassium into the urine than normal. 

• Chronic kidney disease: Most of the time, abnormal kidney function leads to high potassium levels. But sometimes dialysis treatment — which people need when their kidney function falls below a certain level — can remove too much potassium from the blood.

• Endocrine disorders: Conditions like hyperaldosteronism or Cushing’s syndrome can affect the way kidneys handle potassium.

• Genetic disorders: These are more rare. But inherited conditions like Bartter syndrome, Gitelman syndrome, and Liddle syndrome can also increase the amount of potassium in the urine.

Gastrointestinal causes of hypokalemia

The body can also lose potassium from the GI tract rather than from urine. This can happen to anyone with repeated vomiting or diarrhea. This is especially true for people who have:

• Hyperemesis gravidarum (a severe form of morning sickness in pregnant people) 

• Eating disorders, especially bulimia nervosa

• Cyclic vomiting (bouts of uncontrollable vomiting)

• Intestinal conditions, like inflammatory bowel disease

• Laxative use

Medications that causes hypokalemia

There are several medications that can cause hypokalemia, for a variety of reasons. Common ones include:

• Diuretics: These medications increase potassium loss by the way they increase urine production. 

• Antibiotics: Aminoglycoside antibiotics also increase the amount of potassium lost through the urine. And penicillin antibiotics can also cause hypokalemia.

• Insulin: Insulin causes potassium to move from the blood to inside the cells. This means that the potassium blood level is lower, even if the potassium is not leaving the body.

• Albuterol: Asthma inhalers like Albuterol and other beta-agonists have a similar effect as insulin. They cause potassium to shift from the blood to inside the cell.

Alcohol use disorder and hypokalemia

About half of people with chronic alcohol use will have hypokalemia. This happens for several different reasons. People with excessive alcohol consumption can develop hypokalemia from:

• Poor diet: Heavy alcohol use is often linked with malnutrition and/or poor dietary intake, which can affect your potassium levels. 

• Magnesium deficiency: This is also caused by poor dietary intake. And, as explained above, low magnesium levels can cause the kidneys to pull out more potassium into the urine than normal. 

• Poor intestinal absorption, or diarrhea: Heavy alcohol use can prevent your gut from absorbing nutrients from food. Diarrhea from alcohol use can deplete these nutrients, too.

• Nausea and vomiting: As explained above, any condition that leads to vomiting can lower your potassium levels.

• Hormone levels: Changes in hormone levels can increase how much potassium is lost through the urine.

• Alcohol withdrawal: Hormonal changes often occur when someone is in active alcohol withdrawal. This can cause more potassium to be passed through the urine. 

What are the symptoms of hypokalemia?

Hypokalemia often does not cause any symptoms until levels fall below 3.0 mEq/L. If you do have symptoms, they can range from mild to severe. The severity of symptoms depends on more than just the actual number of the blood test. It also depends on how quickly someone’s level drops, as well as the underlying cause.

Symptoms of hypokalemia may include:

• Muscle cramps

• Constipation

• Weakness

• Fatigue 

• Lightheadedness

• Shortness of breath

• Feeling abnormal heart beats or palpitations

Although rare, severe cases of hypokalemia can be life threatening. This is because of the way it affects the heartbeat. Severe hypokalemia can lead to a number of abnormal heart rhythms, which can be too fast or too slow. If someone were to develop one of these rhythms, they would likely lose consciousness. A severe case like this can even lead to full cardiac arrest, although this is very rare. 

Fortunately, most symptoms are reversible with treatment. 

How do you treat hypokalemia?

The treatment for hypokalemia usually requires supplements to get your levels back to normal. This can be done in a couple different ways: 

• For mild to moderate hypokalemia, most people are prescribed oral potassium supplements. 

• Severe cases, especially when the heartbeat is affected, require urgent treatment in the hospital with IV (intravenous) potassium. 

An important part of hypokalemia treatment is addressing the underlying cause. This means treatment may also include:

• Magnesium supplements, if your magnesium level is low

• Blood sugar control

• Medications to help with vomiting or diarrhea

• Lower doses of, or stopping, any medications that are causing hypokalemia

If you know you are prone to low potassium levels, your provider may advise you to increase your intake of potassium-containing foods. According to the World Health Organization, our daily intake of potassium should be at least 3,510 mg (you get about 10% of this in 1 banana).

How long does it take to recover from low potassium?

The amount of time it takes to normalize your potassium level depends on how low your potassium is, and what is causing it. 

If you are taking oral supplements for hypokalemia, it may take several days to weeks to get your potassium level back up. In certain situations, you may need to stay on oral potassium pills long term to counterbalance your body’s loss of potassium. 

When someone has a severe case of hypokalemia, IV treatment will increase their levels faster than pills. It usually only takes 1 to 2 days. 

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Written by:

Nicole Andonian, MD

Nicole Andonian, MD, is a private practice anesthesiologist in Orange County, California. Her focus is in general anesthesia, regional anesthesia, and acute pain management.

Edited by:

Katie E. Golden, MD

Katie E. Golden, MD, is a board-certified emergency medicine physician and a medical editor at GoodRx.

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