What Is Hypokalemia (Low Potassium)?

Medically Reviewed by Jabeen Begum, MD on November 03, 2023
Written by WebMD Editorial Contributors
6 min read

You have hypokalemia when you have low levels of potassium in your blood. Potassium is a mineral your body needs to work normally. It helps muscles to move, cells to get the nutrients they need, and nerves to send their signals. It’s especially important for cells in your heart. It also helps keep your blood pressure from getting too high.

There are many reasons you could have low potassium levels. It can happen when too much potassium leaves your body through your digestive tract. Or, it could be a symptom of another problem.

What is the most common cause of low potassium?

Most often, potassium levels get low when you lose it through your pee after you take medications such as diuretics (water pills) for heart disease or high blood pressure.

Other reasons for potassium loss

You may also develop hypokalemia if you:

It’s possible, but rare, to get hypokalemia from having too little potassium in your diet.

Health conditions that can cause low potassium

Several health conditions may be linked to low potassium, such as:

Women tend to get hypokalemia more often than men.

The symptoms of hypokalemia usually depend on how low your potassium levels are and how long they've been low. If they're low only for a little while, or only a little low, you may not have any symptoms. Or, you might have:

If your potassium levels get more seriously low, you may have:

  • Abnormal heart rhythms (arrhythmia ), especially if you're older
  • Nausea, vomiting, or abdominal bloating
  • Lightheadedness from low blood pressure

If levels are severely low, your muscle tissue might start to break down (rhabdomyolysis). You might have paralysis and even respiratory failure.

If you have low blood potassium for a while, it may affect your kidneys. You may have to go to the bathroom more often. You may also feel thirsty.

 

 

To determine if you have hypokalemia, your doctor will do a potassium blood test to measure the levels of potassium in your blood. They may do this as part of a comprehensive metabolic panel, a series of blood tests that look at how well your kidneys are working and whether levels of minerals called electrolytes are in balance. 

Doctors measure potassium by millimoles per liter (mmol/L).

Normal potassium levels

Potassium levels ranging from 3.5 mmol/L to 5.5 mmol/L are considered normal for adults.

Low potassium levels

If the potassium in your blood serum is below 3.5 mmol/L, you have hypokalemia. If your level is in the range of 3.0-3.4 mmol/L, you have mild hypokalemia, and if your level is lower than 3 mmol/L, you have moderate hypokalemia. If your potassium level is below 2.5 mmol/L, you have severe hypokalemia.

To find out the cause of your low blood potassium, your doctor will ask you about your health history. For instance, they’ll want to know if you’ve had any illnesses that involved vomiting or diarrhea. They’ll also ask about any conditions you might have and any medications you take.

You may take a urine test so your doctor can find out if you’re losing potassium when you pee.

As low potassium sometimes can affect your blood pressure, your doctor will check that, too. They also may want to do an electrocardiogram (EKG) if they think you may have arrhythmia. This is one of the more serious side effects and might change the way your doctor chooses to treat the problem.

 

 

 

 

If your hypokalemia is mild, your doctor may prescribe potassium supplements or recommend an over-the-counter supplement. In most cases, potassium supplements you take by mouth work well.

When your low blood potassium is caused by another medical issue, your doctor will treat that. For instance, if you have low potassium because you take diuretics, your doctor may take you off them or switch you to a different kind. If you have high blood pressure, medicines called angiotensin-converting enzyme (ACE) inhibitors, angiotensin receptor blockers (ARB), or beta-blockers may be an option. They're less likely to cause low potassium levels. (Never stop taking a prescribed medication without talking to your doctor first.)

Even when your doctor changes your medicine, it may take a few weeks to get your potassium levels back to normal. In the meantime, your doctor may have you take potassium supplements. Ask your doctor before taking supplements on your own, as too much potassium can be harmful.

You may need to get potassium by IV in the hospital in some cases, such as:

  • When your potassium level is dangerously low (you have severe hypokalemia)
  • If taking supplements by mouth doesn't raise your potassium levels
  • If your low potassium levels cause abnormal heart rhythms

Emergency treatment and hospitalization

If you have dangerously low potassium levels and/or abnormal heart rhythms, your doctor will give you potassium and other electrolytes by IV in the hospital. You need to be monitored when you get potassium by IV because of the risk of getting too much potassium (hyperkalemia), which can be as dangerous as too little potassium. Once your potassium levels are back up to a safe level, your doctor can address the reason your blood potassium dipped too low and have you take potassium supplements by mouth.

How long does it take to recover from low potassium?

Your recovery time will depend on how low your potassium levels were and how long they were low. It can take several weeks or longer for potassium levels to return to normal. If you get potassium through an IV in the hospital, you may only need treatment for a few days.

If you have diarrhea or are vomiting, drink plenty of fluids. If you're losing lots of fluid through diarrhea and vomiting for more than 1-2 days, talk to your doctor. They may want to test your levels of potassium and other electrolytes.

Avoid drinking too much alcohol (8-15 drinks per week or 4-5 drinks over 2-3 hours, depending on your size and gender).

A diet high in potassium may help prevent hypokalemia. In the U.S., the recommended daily intake of potassium for most adults is between 2,600 and 3,400 milligrams.

Potassium-rich foods

  • Apricots, dried, ½ cup: 755 milligrams
  • Lentils, cooked, 1 cup: 731 milligrams
  • Squash, acorn, mashed, 1 cup: 644 milligrams
  • Prunes, dried, ½ cup: 635 milligrams
  • Raisins, ½ cup: 618 milligrams
  • Potato, baked, flesh only, 1 medium: 610 milligrams
  • Kidney beans, canned, 1 cup: 607 milligrams
  • Orange juice, 1 cup: 496 milligrams
  • Soybeans, mature seeds, boiled, ½ cup: 443 milligrams
  • Banana, 1 medium: 422 milligrams

You have hypokalemia when you have low potassium levels in your blood. This could be for a number of reasons, but often it's because you lose potassium through your pee after you take medications such as a diuretic. Unless your potassium levels are dangerously low, you usually treat low potassium with potassium supplements. To help avoid hypokalemia, drink plenty of fluids when you take a medicine that makes you pee a lot or if you have an illness that makes you vomit or have diarrhea. If you think you have low blood potassium, talk to your doctor.

 

What blocks potassium absorption?

Aside from diuretics and laxatives, some other medicines, such as steroids and some antacids, may either block your ability to absorb potassium or cause you to lose more when you pee and poop. Too much sodium in your diet may cause you to lose more potassium when you pee. Eating a lot of licorice can cause hypokalemia, as well.

What are the risk factors for hypokalemia?

People with some medical conditions, such as inflammatory bowel disease, don't absorb potassium as well as others. Also, people with inflammatory bowel disease usually have chronic diarrhea, which can further decrease potassium levels. Those with pica, a condition where people eat non-food items, have a higher risk of hypokalemia, especially if they eat clay. Clay binds to potassium in your digestive tract, which causes you to lose potassium through your poop.