What Is Hypokalemia?

Hypokalemia refers to a lower than normal level of potassium found through a blood test. “Hypo” means “less than normal,” and the “kal” part of the word comes from “kalium,” (the Latin word for potassium). It can result from many different medical problems, including those affecting the kidney or gastrointestinal tract.

Hypokalemia is a relatively common medical issue. It may occur in 20% or so of hospitalized people and in a much smaller percentage of normal adults. It is the most common type of electrolyte abnormality in hospitalized patients. This is significant because hypokalemia can sometimes cause life-threatening problems, like abnormal heart rhythms.

Hypokalemia Symptoms

Hypokalemia often doesn’t cause any symptoms, especially if it occurs in otherwise healthy adults. However, hypokalemia can cause serious symptoms and problems.

This is particularly likely if a person’s hypokalemia is very severe and the level of potassium in their blood is quite low. Symptoms are also more likely if the level of potassium falls rapidly for some reason.

The nervous system, gastrointestinal system, the kidneys, and the heart can all be affected. This can lead to symptoms like:

• Muscle cramps and pain
• Weakness
• Fatigue
• Paralysis
• Constipation or complete intestinal paralysis (ileus)
• Respiratory failure

Abnormal heart rhythms are one of the most serious potential symptoms, as these can sometimes be deadly. Heart failure is also a possibility. These serious heart problems are much more likely to occur in someone who has underlying heart disease from another cause.

Over the long-term, mild but persistent hypokalemia can also worsen other health conditions, such as chronic kidney disease and high blood pressure.

Causes

To understand the medical causes that can lead to hypokalemia, it’s helpful to understand a little about potassium’s role in the body and the way in which it moves through it.

How Potassium Works

Potassium is one of the body’s important electrolytes. These are tiny particles that carry a positive or negative charge. Electrolytes such as potassium are dissolved in your body’s fluids, both inside cells and outside them. In the case of potassium, its concentration is much greater inside cells than in the bloodstream itself.

Potassium and other electrolytes play several important physiological jobs, but one of the most important is their role in sending electrical signals via the body’s nervous system. So it’s not surprising that abnormalities in potassium lead to signaling issues in the electrical systems of the heart and in the nervous system.

The concentration of electrolytes is monitored very carefully by your body, so that they can be kept in a tight range. That’s important because levels that are too high or too low can cause problems and even death. However, even with complex regulatory mechanisms, sometimes the concentration of potassium in the blood gets too low.

Underlying Causes of Hypokalemia

A person’s blood can become low in potassium if they haven’t been taking in enough through their diet. This is a relatively uncommon cause, as most people get enough potassium from the foods they eat. But not eating enough potassium can worsen the problem if another cause is present.

It’s much more common that issues arise when too much potassium is leaving the body, through the gastrointestinal tract or through the urine. In these cases, a person doesn’t have enough total potassium in their body, so that shows up as hypokalemia on a blood test.

Hypokalemia can also occur when something triggers more potassium than normal to move from the blood to inside the cells. In this situation, the total amount of potassium in the body might be normal, but there isn’t enough potassium in the blood specifically. For example, this can happen when a person takes too much insulin.

Some of the potential underlying causes of hypokalemia include:

• Prolonged diarrhea or vomiting
• Polydipsia
• Certain kidney issues (such as renal tubular acidosis)
• Dialysis treatment
• Cushing syndrome
• Hyperaldosteronism
• Thyrotoxicosis
• Low levels of magnesium
• Rare genetic syndromes (like familial hypokalemic period paralysis)

Another trigger that deserves specific mention is hypokalemia from medical interventions. For example, this can happen when a person is given large amounts of intravenous fluids in the hospital that don’t
contain enough potassium.

Medications are also a major potential cause. Diuretics are a particularly common trigger for hypokalemia. Loop diuretics (like Lasix), thiazide diuretics (like hydrochlorothiazide), and osmotic diuretics (like mannitol) all can cause hypokalemia as a potential side effect.

Some other medications that might cause hypokalemia are:

• Corticosteroids (like prednisone)
• Laxatives
• Decongestants
• Insulin overdose
• Certain antibiotics (including amphotericin B and penicillin)
• Certain drugs for asthma (including albuterol)

Diagnosis

Commonly, a person found to have hypokalemia is already receiving medical attention for a specific medical problem.

Hypokalemia itself can be easily diagnosed as part of a common set of blood tests, a basic metabolic panel, or through a slightly larger set of tests called a complete metabolic panel.

These tests check the concentrations of several substances in the blood, including electrolytes like potassium. These panels are often run as part of an initial medical workup or as part of general monitoring while a person is hospitalized.

The normal concentration of potassium in the blood is between 3.5 mmol/L and 5.1 mmol/L. If the concentration is less than that, the individual has hypokalemia. Levels between 3.0 mmol/L and 3.5 mmol/L often don’t cause symptoms. Below 2.5 mmol/L is considered severe hypokalemia. (If above 5.1, an individual has hyperkalemia instead.)

However, that’s only the starting place. It’s important to figure out the underlying cause of the hypokalemia to make sure it can be adequately treated.

A detailed medical history is key, including recent symptoms, current medications, and long-term health problems like heart disease. A thorough medical exam is also fundamental, one performed with special attention to heart and nervous system issues.

The likely underlying cause is often apparent from these alone. For example, if someone has been repeatedly vomiting from a stomach virus, that is probably the cause of the hypokalemia.

However, other tests in addition to a basic metabolic panel might be necessary in some circumstances. These might include:

• Repeat potassium blood tests
• Urine tests of electrolytes
• Arterial blood gas
• Tests for magnesium blood levels (if not already performed)

Other tests may also be needed if additional symptoms point to specific underlying causes (e.g., thyroid function tests if symptoms of thyrotoxicosis are present).

Some people will also need to have their heart rhythm checked via an EKG, especially if a person has symptoms from hypokalemia, extremely low potassium, known heart disease, or other conditions that worsen the risk of heart rhythm problems. Certain changes on the EKG may indicate that a person is at high risk of having an abnormal heart rhythm, warranting immediate emergency treatment.

Treatment

Treatment for hypokalemia focuses on raising the potassium level and addressing underlying causes.

Intravenous Potassium

People with these signs of potentially serious problems from hypokalemia need rapid treatment with intravenous potassium. That is the quickest way to get the potassium in the blood up to the normal level.

However, this needs to be monitored with repeat potassium blood tests and sometimes with continuous monitoring via an EKG. If a person is given too much potassium too quickly, it can lead to hyperkalemia, leading to potentially serious symptoms as well.

Oral Potassium

However, for most people oral potassium will correct the problem and intravenous potassium isn't advised. Oral potassium generally carries less risk of causing hyperkalemia. Depending on the situation, this can be taken over a few days to a few weeks. A variety of different preparations of oral potassium are available, and your healthcare provider can prescribe a specific version.

Trying to increase potassium intake through the diet may also be helpful. For example, some of the following foods are high in potassium:

• Dried fruits
• Nuts
• Spinach
• Potatoes
• Bananas
• Avocados
• Bran cereals

However, oral supplements of potassium for a period are usually needed as well, unless the hypokalemia is very mild.

Addressing Other Underlying Issues

Sometimes it’s also appropriate to adjust medications if those have contributed to the problem. For example, one might need to stop taking a diuretic, or switch to a different type of diuretic (a “potassium-sparing diuretic”) that isn’t likely to decrease potassium levels, like amiloride.

If a person needs to keep taking a medication that lowers potassium, they may have to take an oral potassium supplement long-term. Similarly, if a medical condition is continuing to cause potassium to be lost, a person might need to take potassium supplements long-term.

If someone has low levels of magnesium in the blood as well as hypokalemia, they will also need treatment with magnesium. Because of the way these two electrolytes are co-regulated in the body, levels of one affect the other. Even with potassium treatment, potassium levels may not return to normal in someone who also has untreated low magnesium.

It’s also important to address the underlying cause. For example, someone might develop hypokalemia from Cushing syndrome that developed from a type of tumor of the adrenal gland. One needs to treat this issue to address the hypokalemia as well. For some medical problems, additional potassium is not needed if the underlying issue can be successfully treated.

Prognosis

Fortunately, symptoms from hypokalemia usually go away after adequate treatment with potassium. A single instance of hypokalemia doesn't usually cause long-term problems.

However, it's important to note that some individuals who experience an abnormal heart rhythm due to hypokalemia do die. For people with an underlying heart condition, like congestive heart failure, it's especially important to get hypokalemia treated promptly. That's because having hypokalemia in addition to such a condition may increase the risk of death.

A Word From Verywell

Hypokalemia is a common medical issue, one often picked up on a laboratory test done for routine testing. Fortunately, it’s usually not a major problem. But it is one that needs to be taken seriously, particularly if it is severe or if you have an existing heart condition. If detected, talk to your healthcare team about how it will be treated and monitored.