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Potassium Test: Why and How Is It Done?

Medically reviewed by Regina Victoria Boyles, MD · Pediatrics

Written by Nikita Bhalla · Updated 5 days ago

    Potassium Test: Why and How Is It Done?

    A potassium test specializes in evaluating the level of potassium in the human blood and indicating whether the potassium level is within the normal range. Potassium is an electrolyte that fuels cells and organs to function efficiently. To be specific, it boosts the smooth functioning of nerves and muscles. Electrolytes get transformed to ions when placed in a solution, after which they can conduct electricity.

    Minor fluctuations in potassium levels in the blood may lead to serious health conditions due to electrolyte imbalance. Your doctor may recommend this test as a part of a regular check-up or if they suspect that you may be suffering from electrolyte imbalance.

    Why Is a Potassium Test Done?

    A potassium test or K+ blood test is usually a part of the electrolyte panel that comprises a group of blood tests. Apart from taking this medical test as a part of your routine check-up, if your doctor suspects certain specific health conditions, they may advise you to take this test. The following are the factors that a potassium test can analyze and monitor:

    • Checking electrolyte balance
    • Understanding the root cause of paralysis attack (or sudden weakness)
    • Diagnosing medical conditions of kidneys
    • Evaluating a health condition called alkalosis, a medical condition arising when body fluids contain abnormal levels of alkali.
    • Evaluating the health conditions of the heart
    • Analyzing high levels of blood pressure
    • Monitoring the actions of certain medications that affect potassium levels, especially diuretics, high blood pressure, and heart medications
    • Checking metabolic acidosis, a health condition that occurs because of the inability of kidneys to remove sufficient acid from the body or when the body produces excess acid, as in the case of uncontrolled diabetes

    Prerequisites of a Potassium Test

    It is usually advised that you do not eat for a minimum of 6 hours before taking the potassium test. However, drinking water is usually not discouraged. Inform your doctor about the medications that you might be taking — prescription drugs, OTC (over-the-counter) drugs, vitamins, supplements, and herbals.

    Also, share your family and personal medical history, and medications that you may be allergic to with your doctor. It will enable him/her to advise you whether you need to stop taking a certain drug for a specific period of time before undergoing this test. This is because there are some medications that may affect the results of the K+ blood test if consumed a few hours or days before taking the test.

    Potassium Test: Understanding the Results

    A normal range for potassium test is between 3.6 and 5.2 millimoles per liter. However, this range often varies amongst different laboratories. Despite the potassium content in blood being negligible, it is such an essential part of our bodily functions that even a slight increase or fall leads to health problems. 

    Let’s take a look at the reasons that can cause an increase (hyperkalemia) or decrease (hypokalaemia) in potassium levels.

    Some of the possible reasons of hypokalaemia or low potassium levels in the blood include:

    • Excessive sweating
    • Lack of folic acid
    • Chronic kidney diseases
    • Lack of potassium as a part of the diet
    • Excessive use of laxatives
    • Gastrointestinal disorders like chronic vomiting and diarrhea
    • Consumption of certain diuretics
    • Diabetes, especially after taking insulin
    • Acetaminophen overdose
    • Cushing’s syndrome or exposure to high levels of the hormone called cortisol or consumption of certain steroid hormones
    • Hyperaldosteronism, as a result of the excessive release of the hormone aldosterone from the adrenal gland
    • Certain medications such as antifungals, antibiotics, corticosteroids, anti-psychotic drugs and bronchodilators

    What Causes Hyperkalemia?

    Level of potassium in blood of over 7.0 millimoles per litre can be life-threatening. Some of the possible reasons of hyperkalaemia or higher than normal levels include:

    • During blood transfusion
    • Breakdown of muscle fibres as a result of injury of tissues
    • Type 1 diabetes
    • Dehydration
    • Infection
    • Excessive potassium in the diet or due to the intake of potassium supplements
    • Serious physical injury or burns that have destroyed red blood cells
    • Failure of the kidneys
    • Respiratory acidosis that arises when the lungs cannot get rid of carbon dioxide generated by the body, which increases the acidity of the fluid
    • Metabolic acidosis that arises due to excessive production of acid or the inability of the kidneys to remove sufficient acid from the body
    • Hypoaldosteronism or a condition that arises due to the dysfunction or deficiency of the hormone called aldosterone
    • Addison’s disease, or adrenal glands don’t produce sufficient hormones
    • Certain specific medications like non-steroidal anti-inflammatory drugs (NSAIDs), angiotensin II receptor blockers (ARBs), beta-blockers, diuretics, and ACE enzyme inhibitors

    There are certain situations that can lead to inaccuracies in the potassium test results. For instance, potassium level may increase when you relax and close your fist tight while collecting blood. Shaking the blood sample test tube/vial may lead to the potassium leaking out of the cells and onto the serum. Under such circumstances, your doctor will probably advise you to go for a repeat K+ test.

    potassium test

    Potassium Test: When Should It Be Repeated?

    If your doctor suspects inaccuracies in your test result, they may recommend that you go for a repeat blood test.

    To monitor certain health conditions, the doctor may advise repeating the K+ test at regular intervals.


    A medical practitioner selects a vein, usually on the back of your hand or inside of your elbow, to draw blood with an injection. They will  collect the blood in th vial and send it to the laboratory for testing under a microscope. The chosen part of the limb is wrapped tightly with a band and antiseptic is spread across the area to clean it. After blood collection, the healthcare practitioner will remove the needle and the wrap. The needle insertion area is then covered with a small bandage. It usually takes a few minutes to generate the K+ blood test results.

    There may be some side effects of the blood tests or extraction in general, though they are rare. Some of these risks are:

    • Lightheadedness 
    • Bruising
    • Bleeding
    • Fainting
    • Skin infection, in extreme cases, when the skin is broken

    Learn more about Kidney Disease here.


    Hello Health Group does not provide medical advice, diagnosis or treatment.

    Medically reviewed by

    Regina Victoria Boyles, MD


    Written by Nikita Bhalla · Updated 5 days ago

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