Test Quick Guide

Potassium is a mineral found throughout your body that is essential to your health. It is one of several electrolytes that helps control your body’s fluid levels, acid-base balance, as well as nerve and muscle activity. Potassium is predominantly present inside cells throughout the body, and its level in the liquid portion of blood is regulated by the kidneys.

Most potassium tests measure the amount of potassium in the liquid portion of your blood (serum or plasma), but a urine potassium test is also used in some situations. These tests can determine whether you have normal levels of potassium. If potassium levels are too high or too low, it can cause numerous symptoms and health risks, and can be life-threatening.

Potassium can be measured individually, but it is often included in broader tests such as an electrolyte, renal, or basic or comprehensive metabolic panel.

About the Test

Purpose of the test

Tests that measure potassium have multiple applications in clinical medicine. Whether potassium is tested alone or as part of a panel, it can be part of diagnosis, monitoring, or screening evaluation.

After signs or symptoms of a health problem have occurred, diagnosis is the process of finding the cause. High or low potassium levels can cause multiple types of symptoms, which can prompt potassium testing. An imbalance in electrolytes can affect virtually all body systems, so panel tests are frequently used to diagnose many different disorders.

Because the kidneys are centrally involved in regulating potassium levels, a potassium test is often used to help evaluate the status of your kidneys. Potassium also plays an important role in healthy heart function. It is involved in the electric signal functioning of the heart muscle, so potassium levels are frequently checked if you have heart-related symptoms.

Potassium tests are also used for monitoring, which is testing that tracks your condition over time. When treatment is given for abnormal potassium levels, repeat testing can indicate how well that treatment is working. Repeat testing of potassium alone or in a panel can also be part of the ongoing evaluation of the kidneys or cardiovascular system.

Measuring potassium and other electrolytes is common if you are in the hospital or are taking many different kinds of medications. A proper electrolyte balance is vital for maintaining fluid levels, acid-base balance, and overall health, so regular monitoring of potassium and other electrolytes is frequently done in these settings.

Screening is often called early detection because it is testing that happens before there are any signs or symptoms of a health problem.

With potassium testing, screening is most common in people who have a higher risk for kidney or cardiovascular disease, such as those with diabetes or high blood pressure. This testing is not standard for healthy adults without this elevated risk, but some primary care doctors may include it as part of blood testing during routine checkups for adults.

When tested for screening, potassium is usually part of a panel that also measures other electrolytes. Panel tests for screening may also include other proteins and compounds in the blood that can inform the doctor about kidney function.

What does the test measure?

A potassium test measures the amount of the mineral in a blood (serum or plasma) or urine sample.

Potassium, an essential nutrient found throughout the body, is necessary for healthy cell activity. Without potassium, the heart and other muscles cannot function.

Diet, made up of the foods and drinks you consume, is the source of potassium. Some people also obtain potassium from dietary supplements.

Under normal circumstances, your body absorbs and stores the potassium it needs, and the kidneys primarily remove any excess through urine. In this way, a potassium measurement can detect disruptions to how the body stores, uses, and excretes potassium.

Blood levels of potassium are frequently measured in a panel test along with other electrolytes, including sodium, chloride, and bicarbonate.

In some urine potassium tests, creatinine is measured along with potassium. A waste material that is a byproduct of muscle activity, creatinine is excreted at a relatively steady pace daily. Simultaneous measuring urine creatinine normalizes the potassium excretion, independent of how many fluids you consume before the test and how diluted your urine is, without having to do a full 24-hour urine collection.

When should I get this test?

There are diverse circumstances in which a potassium test can be prescribed.

For diagnosis, a potassium blood test is usually performed if you have symptoms that could be related to an abnormal potassium level. Examples of symptoms of high potassium include an irregular heartbeat, muscle weakness, and nausea. Low potassium can cause heartbeat changes, fatigue, muscle cramps and twitches, nausea, and constipation.

Measurement of electrolytes, including potassium, is frequently done if the doctor suspects that you have possible heart issues, kidney problems, or a disturbance of the body’s acid-base balance.

In addition, electrolyte testing is common if you have general symptoms or are being evaluated in an emergency room or urgent care clinic. Because electrolytes play a role in all bodily functions, this testing, including measuring potassium, can help identify an underlying cause of pressing health problems.

Most potassium testing is blood testing, which is used to diagnose high potassium levels, known as hyperkalemia, or low potassium, called hypokalemia. However, in some cases, urine potassium testing is needed to help determine why levels are low.

For monitoring, potassium and other electrolyte tests may be repeated multiple times at regular intervals to detect any abnormal changes. This is often done if you take medications that can affect your kidneys or overall electrolyte balance. If you are taking diuretics or other intravenous drugs in the hospital, you may have frequent monitoring with electrolyte tests.

Screening for abnormal potassium levels typically occurs as part of a panel test performed during routine medical checkups. While doctors can prescribe this testing for any patient, it is usually reserved if you have high blood pressure, diabetes, or a family history of kidney problems.

Finding a Potassium Test

How can I get a potassium test?

The standard potassium test uses a blood sample obtained with a blood draw at your doctor’s office, a hospital, or a laboratory.

Urine tests for potassium are less common. When needed, they are normally conducted with one of two methods:

  • A 24-hour urine sample: This involves collecting all of the urine you produce over a full day so the laboratory can measure the total amount of potassium you excreted during that time.
  • A spot urine sample measuring the potassium-to-creatinine ratio: This method involves a one-time urine sample at a lab or medical office. Comparing the amount of potassium to creatinine in this sample allows the lab to estimate your 24-hour potassium excretion.

Blood and urine tests are normally done after being prescribed by a doctor or other health professional. You can also order a blood potassium test or urine potassium test online.

Can I take the test at home?

You can take a potassium test at home, either with a blood or urine sample.If using a 24-hour urine test, you will need to collect your urine wherever you are during the day. For blood tests, you often need to visit a local laboratory to have your sample collected.

How much does the test cost?

The cost of a potassium test can change based on several factors, including:

  • Whether potassium is measured alone or as part of a panel test
  • Whether the test uses a blood or urine sample
  • Where the test sample is collected
  • Whether you have health insurance coverage

The final cost of a potassium test can involve several components including charges for office visits, technician fees for taking your sample, and/or charges for laboratory evaluation.

Your insurance company may pay for some or all of these costs if your doctor prescribes your potassium test. For the most definitive information about likely costs, talk with your doctor’s office and medical insurance company.

Taking a Potassium Test

Blood tests are the most common type of potassium test. A blood sample is taken in a medical lab, hospital, or doctor’s office for this test.

For a urine potassium test, you may provide a one-time sample at a medical office or lab, or you may be asked to do a 24-hour sample in which you collect all of the urine you produce over a day in special containers.

Before the test

If you are having a blood test for potassium alone, you usually will not have to follow any special preparation for the test. Yet if you have potassium tested as part of a panel test like a basic or comprehensive metabolic panel, you may need to fast for 8 to 12 hours beforehand. Check with your doctor whether you can eat and drink before the blood draw.

For either a blood or urine test, you may need to temporarily stop taking certain medications beforehand. Some prescription or over-the-counter drugs and some dietary supplements can affect potassium levels. Your doctor can tell you whether you need to adjust your normal medications prior to your test.

During the test

For a potassium blood test, a blood sample will be taken from a vein in your arm. Most of the time, an elastic band called a tourniquet will be tied around your upper arm. This increases blood flow in your arm and makes it easier to access the vein.

The technician will use an antiseptic wipe on your skin near the vein and insert a needle. A vial of blood will be withdrawn, and then the needle will be taken out.

The total blood draw usually lasts only a few minutes. There may be some pain during the procedure, and many people feel a brief sting when the needle is inserted.

For a spot urine test that measures the potassium-to-creatinine ratio, you will be given a receptacle to collect urine in the bathroom at the doctor’s office or lab. Normally you will be instructed to start urinating into the toilet and then collect a sample by holding the receptacle under your stream of urine.

For a 24-hour sample, you will be given bags or containers for collecting your urine for a full day. You will need to have a container with you throughout the day to collect urine regardless of where you are.

For the standard 24-hour collection, you will start the day by urinating in the toilet after waking up. Then you will collect all your urine for the rest of the day and night. You will also collect the urine from when you first wake up the next day. Once you have finished the 24-hour collection, follow the instructions for bringing your sample to the lab.

After the test

After a potassium blood test, a cotton swab or bandage will be placed over the puncture site to stop any bleeding. You can return to most normal activities once the test is over. Slight pain or bruising can affect your arm but normally goes away quickly.

There are few or no lasting effects from potassium urine tests. Once you have provided a spot or 24-hour urine sample, you can engage in daily activities without restrictions.

Potassium Test Results

Receiving test results

In most cases, results for both blood and urine potassium tests are available within a period of a few business days.

Test results can be sent by mail or accessible through online health portals. You may also receive a call or email from your doctor to either review your results or schedule a follow-up appointment.

Interpreting test results

Interpretation of a potassium test requires carefully considering the result, the laboratory reference range, and your health situation. Because potassium is frequently measured with other electrolytes, levels may be evaluated together.

For a blood test, the report should list the amount of potassium measured in either milliequivalents per liter (mEq/L) or millimoles per liter (mmol/L). The test report will also show a reference range, which the laboratory considers an expected range for potassium levels.

A common reference range for potassium is from around 3.5 to 5 mmol/L, although there can be slight variation between laboratories. For this reason, it is important to look for the specific reference interval listed on your test report.

Too much potassium in the blood is called hyperkalemia. This can signify that the kidneys are not properly removing excess potassium from the blood and excreting it from the body in urine. It is often related to certain medications that prevent the kidneys from regulating potassium levels, but other kidney disorders (such as acute or chronic kidney failure) may also cause it.

High potassium levels can also occur when too much potassium is released into the blood from inside cells where it is normally stored. This can be caused by burns or other injuries (eg, severe tissue trauma, hemolysis), and conditions that affect the acid-base balance in the body.

In many cases, high potassium levels are the result of multiple causes. Increasing potassium intake from diet or supplements rarely causes hyperkalemia alone. Still, when paired with reduced kidney function or other contributing factors, increased intake may spur a rise in blood levels of potassium.

False hyperkalemia may occur if blood samples are not collected and handled properly. For example, if red cells are destroyed during the collection procedure.

Too little potassium in the blood is known as hypokalemia. Hypokalemia most often can happen after taking diuretic medications that increase urination. Diarrhea, vomiting, and profuse sweating may also cause fluid loss that diminishes blood levels of potassium. Less often, hypokalemia results from insufficient potassium intake due to poor diet or health conditions that increase the amount of potassium stored in cells.

Urine potassium tests are normally only used if a blood potassium test is abnormal. For a urine potassium test, your report will show either the total level of potassium measured in a 24-hour sample or the ratio of potassium to creatinine in a one-time urine sample.

The report should show the laboratory’s reference range for urine potassium levels as with a blood test. Checking this reference range is important because laboratories can vary depending on their measurement methods.

Causes of abnormal urine potassium levels are often similar to the causes that can affect blood potassium levels. When urine potassium is measured, it may help doctors identify the most likely cause of abnormal levels, including whether the kidney is properly enabling potassium excretion from the body.

Asking questions can help you understand the meaning of your potassium test results. When you talk with your doctor, some of these questions may be helpful to review:

  • Was my potassium level low, normal, or high?
  • Were any other measurements taken along with potassium? If so, were they normal or abnormal?
  • If my potassium was too high or too low, what is the most likely cause?
  • Are there any follow-up tests that you recommend?
  • Should I have another potassium test?
  • Should I make any changes to my diet?


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