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This article waslast modified on 24 July 2018.
At a Glance
Why Get Tested?

To diagnose levels of potassium that are too high (hyperkalaemia) or too low (hypokalaemia)

When To Get Tested?

As part of a routine medical examination or to investigate a serious illness, such as high blood pressure or kidney disease

Sample Required?

A blood sample taken from a vein in the arm

Test Preparation Needed?


On average it takes 7 working days for the blood test results to come back from the hospital, depending on the exact tests requested. Some specialist test results may take longer, if samples have to be sent to a reference (specialist) laboratory. The X-ray & scan results may take longer. If you are registered to use the online services of your local practice, you may be able to access your results online. Your GP practice will be able to provide specific details.

If the doctor wants to see you about the result(s), you will be offered an appointment. If you are concerned about your test results, you will need to arrange an appointment with your doctor so that all relevant information including age, ethnicity, health history, signs and symptoms, laboratory and other procedures (radiology, endoscopy, etc.), can be considered.

Lab Tests Online-UK is an educational website designed to provide patients and carers with information on laboratory tests used in medical care. We are not a laboratory and are unable to comment on an individual's health and treatment.

Reference ranges are dependent on many factors, including patient age, gender, sample population, and test method, and numeric test results can have different meanings in different laboratories.

For these reasons, you will not find reference ranges for the majority of tests described on this web site. The lab report containing your test results should include the relevant reference range for your test(s). Please consult your doctor or the laboratory that performed the test(s) to obtain the reference range if you do not have the lab report.

For more information on reference ranges, please read Reference Ranges and What They Mean.

What is being tested?

Potassium is present in all body fluids, but most potassium is within your cells, with only a very small amount in the serum or plasma component of the blood. If potassium goes too low or too high, your health may be impaired. An abnormal concentration can alter the function of the nerves and muscles; for example, in extreme cases you may experience heart rhythm disturbances or the heart muscle may even lose its ability to contract.

How is the sample collected for testing?

A blood sample is taken by needle from a vein in the arm.

Is any test preparation needed to ensure the quality of the sample?

No test preparation is needed.

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Common Questions
  • How is it used?

    Blood tests are performed to diagnose concentrations of potassium that are too high (hyperkalaemia) or too low (hypokalaemia). The most common cause of hyperkalaemia is kidney disease, but many drugs can decrease the amount of potassium excreted from the body and result in this condition. Hypokalaemia can occur if you have severe diarrhoea and vomiting, due to loss of potassium and dehydration. Potassium can also be lost through your kidneys in urine; in rare cases, potassium may be low because you are not getting enough in your diet. Drugs can cause your kidneys to lose potassium, particularly diuretics ('water pills'), resulting in hypokalaemia. Once your doctor discovers the reason for the too-high or low potassium concentration in the blood, it can be treated.

  • When is it requested?
  • What does the test result mean?

    A raised blood potassium concentration is called hyperkalaemia. This may indicate the following health conditions:

    Certain drugs can also cause hyperkalaemia in a small percent of patients. Among them are non-steroidal anti-inflammatory drugs (such as ibuprofen); beta-blockers (such as propanolol and atenolol), angiotensin-converting enzyme (ACE) inhibitors (such as captopril, enalapril, and lisinopril), and potassium-sparing diuretics (such as triamterene, amiloride, and spironolactone).

    A low blood concentration of potassium is called hypokalaemia. and may occur in a number of conditions, including:

    • vomiting,
    • diarrhoea, and
    • insufficient potassium intake (this is rare).

    If you have diabetes, your potassium concentration may fall after you take insulin, particularly if your blood glucose levels have been out of control for a while. Low potassium is commonly due to 'water pills' (diuretics); if you are taking these, your doctor will check your potassium level regularly.

  • Is there anything else I should know?

    The way that your blood is taken and handled may cause the potassium concentration in the sample to be falsely high. If you clench and relax your fist a lot while your blood is being collected, this can make potassium concentration in the blood rise. If blood comes out of your veins too fast or too slow, the blood cells can burst and release potassium into the blood, giving a falsely raised potassium result. Some tubes that are used to collect blood sample into contain potassium salts as a preservative. If your blood sample is collected into one of these tubes by mistake, the potassium concentration in the sample will be falsely high.  

    Potassium can also be elevated if the specimen takes a long while to travel from your GP surgery to the laboratory.

    If there are any questions as to how your blood was collected, your doctor may request that the test be repeated before starting any treatment.

  • What are appropriate treatments for the common causes of low potassium (hypokalaemia) and high potassium (hyperkalaemia)?

    Treatment for hypokalaemia may include the use of potassium chloride supplements and increasing the amount of potassium-rich foods in the diet, such as bananas, beef, or spinach. Treatment for hyperkalaemia may include the use of diuretics, kidney dialysis, or insulin injections.

  • What are some good dietary sources of potassium?

    A number of fruits, vegetables, and meats are good sources of potassium. Examples are bananas, melons, orange juice, potatoes, spinach, broccoli, milk, yoghurt, turkey and beef.

  • Is there an over-the-counter test I can use to check my potassium levels?

    No. Electrolyte tests are performed by trained scientists using highly sensitive instruments in accredited laboratories.

  • Would a sports drink help with my electrolyte levels?

    Sports drinks offer a quick replacement of electrolytes, but your body can replenish them naturally using its own storage supply of minerals.