When you have a routine health exam; when you have symptoms such as muscle weakness and/or irregular heart beat (cardiac arrhythmia) or when an electrolyte imbalance is suspected; at regular intervals when you are taking a medication and/or have a disease or condition, such as high blood pressure (hypertension) or kidney disease, that can affect your potassium level
Potassium is an electrolyte that is vital to cell metabolism. It helps transport nutrients into cells and removes waste products out of cells. It is also important in muscle function, helping to transmit messages between nerves and muscles. This test measures the amount of potassium in the blood and/or urine.
Electrolytes are minerals that carry a charge and exist in your body fluids. Potassium and other electrolytes such as sodium, chloride, and bicarbonate (total CO2) help regulate the amount of fluid in the body and maintains a stable acid-base balance. Potassium is present in all body fluids, but most potassium is found within the cells. Only a small amount is present in fluids outside the cells and in the liquid part of the blood (called serum or plasma).
We get most of the potassium we need from the foods that we eat. Most people will have an adequate intake of potassium. The body uses what potassium it requires, then the kidneys eliminate the rest in the urine. The body tries to keep the blood potassium level within a very narrow range. Levels are mainly controlled by aldosterone, a hormone produced by the adrenal glands above the kidneys.
Because the blood concentration of potassium is so small, minor changes can have significant health effects. Potassium levels that are too low or too high can alter the function of the nerves and muscles and there can be serious health complications, such as shock, breathing problems (respiratory failure), irregular heart beat, or the heart muscle may even lose its ability to contract.
Measuring potassium as part of an electrolyte or metabolic panel may help diagnose an electrolyte imbalance or acidosis or alkalosis. Acidosis and alkalosis describe the abnormal conditions that result from an imbalance in the pH of the blood caused by an excess of acid or alkali (base). This imbalance is typically caused by some underlying condition or disease.
How is the test used?
A potassium blood test is used to detect abnormal potassium levels, including high potassium (hyperkalemia) and low potassium (hypokalemia). It is often used as part of an electrolyte panel or basic metabolic panel for a routine health exam.
The potassium test may also be used:
- To help detect, evaluate, and monitor electrolyte imbalances and/or acid-base (pH) imbalances (acidosis or alkalosis)
- To help evaluate and monitor a variety of chronic or acute illnesses, such as high blood pressure or kidney disease, the most common cause of high blood potassium
- To detect abnormal values when you have diarrhea and vomiting or excessive sweating
- To help determine the cause of symptoms involving the heart (e.g., irregular heart beat)
- To monitor effects of drugs that can cause the kidneys to lose potassium, particularly diuretics, or drugs that decrease potassium elimination from the body, which may result in a high potassium level
Urine potassium levels may be tested in people who have abnormal blood potassium levels to help determine the cause, such as dehydration. Urine potassium testing is also used for people with abnormal kidney tests to help the healthcare practitioner determine the cause of kidney disease and to help guide treatment.
When is it ordered?
A potassium level is a basic test and may be ordered when you have a routine medical exam or when you are being evaluated for a serious illness.
Testing may be done when you have:
- Kidney disease
- Symptoms such as muscle weakness or irregular heart beat (cardiac arrhythmia)
- A condition treated with diuretics or heart medications
- Has high blood pressure (hypertension) or are being treated for high blood pressure
Electrolyte panels and basic metabolic panels are commonly ordered at regular intervals when a healthcare practitioner is diagnosing diabetic ketoacidosis and kidney disease or when monitoring a patient receiving dialysis, diuretic therapy, or intravenous fluids.
Urine potassium testing may be done when blood potassium levels are abnormal.
What does the test result mean?
Potassium levels are typically interpreted along with results from other tests done at the same time, such as the results of other electrolyte tests. Low and high potassium levels can be caused by various conditions and diseases.
Examples of conditions that can cause high potassium levels (hyperkalemia) include:
- Kidney disease
- Addison disease
- Injury to tissue
- Consuming too much potassium (e.g., diets high in potassium, potassium supplements)
- Treatment with intravenous (IV) fluids, excessive IV potassium
- Using certain drugs that cause high potassium in a small percent of people, including non-steroidal anti-inflammatory drugs (NSAIDs), ACE inhibitors, beta blockers (such as propranolol and atenolol), angiotensin-converting enzyme inhibitors (such as captopril, enalapril, and lisinopril), and potassium-sparing diuretics (such as triamterene, amiloride, and spironolactone)
Examples of conditions that can cause low potassium levels (hypokalemia) include:
- Diarrhea and vomiting
- Primary hyperaldosteronism (Conn syndrome)
- A complication of acetaminophen overdose
- Diabetes - the potassium level may fall after you take insulin, particularly if you have not managed your diabetes well.
- As a side-effect of "water pills" (potassium-wasting diuretics); if you take these, your healthcare provider may check your potassium level regularly.
- Use of certain drugs such as corticosteroids, beta-adrenergic agonists such as isoproterenol, alpha-adrenergic antagonists such as clonidine, antibiotics such as gentamicin and carbenicillin, and the antifungal agent amphotericin B
Potassium urine levels are usually compared with blood levels. The body normally eliminates excess potassium, so the urine level may be elevated because it is elevated in the blood. Urine potassium may also be elevated when the body is losing too much potassium. In this case, the blood level would be normal to low. If blood potassium levels are low due to not consuming enough, then urine concentrations will also be low.
My potassium level is only slightly out of range. What does this mean?
Your potassium result is interpreted by your healthcare practitioner within the context of other tests that you have had done as well as other factors, such as your medical history. A single high or low result may or may not have medical significance. Generally, this is the case when the test value is only slightly higher or lower than the reference range. This is why healthcare practitioners may repeat a test on you and why they may look at results from prior times when you had the same test performed.
On the other hand, a result outside the range may indicate a problem and warrant further investigation. Your healthcare practitioner will evaluate your test results and determine whether a result that falls outside of the reference range means something significant for you.
What are appropriate treatments for the common causes of low potassium (hypokalemia) and high potassium (hyperkalemia)?
What are some good dietary sources of potassium?
Is there a home test I can use to check my potassium level?
Is there anything else I should know?
Potassium levels can be falsely elevated by a variety of circumstances surrounding specimen collection and specimen processing. For example, if you clench and relax your fist repeatedly while your blood sample is drawn, the potassium level in the blood may increase. If blood samples are delayed in getting to the lab or if the blood tubes are subjected to rough handling in transit, potassium may leak from red blood cells and falsely elevate the potassium in the serum. A healthcare practitioner may question elevated potassium results when the numbers do not fit the clinical condition. If there are any questions as to how the blood was collected, the healthcare practitioner may request that the test be repeated to verify results.