Potassium Test

The test is performed to identifyconcentrations of potassium that are too high (hyperkalaemia) or too low (hypokalaemia). Potassium is typically measured along with sodium and creatinine as part of a “renal function test”. The test may be conducted as part of routine health screening or for monitoring of patients with conditions that are known to cause abnormalities in potassium . The test is also used to monitor patients taking drugs that can effect potassium excretion.

Once your doctor discovers the reason for the abnormal potassium concentration in the blood, it can be treated.

Blood potassium concentrations are frequently measured as part of routine health screening and in the clinical investigation of many diseases. It is measured in those who take diuretics or heart medications, and in the investigation of high blood pressure and kidney disease. It is also used to monitor patients on kidney dialysis or diuretic therapy, and patients receiving intravenous therapy on a drip.

A raised blood potassium concentration is called hyperkalaemia. Kidney disease is a common cause of hyperkalaemia. In this condition the body is less able to excrete potassium in the urine and so the levels within the blood rise. Some drugs also decrease the kidney’s ability to excrete potassium potentially leading to hyperkalaemia. Among them are non-steroidal anti-inflammatory drugs (such as ibuprofen) and drugs used to treat high blood pressure such as angiotensin-converting enzyme (ACE) inhibitors (such as captopril), and potassium-sparing diuretics (such as spironolactone). There are many other conditions that can cause hyperkalaemia, including diabetes and Addison disease. In hospitalised patients, hyperkalaemia may occur if the patient is given too much potassium in a drip.

A low blood potassium concentration is called hypokalaemia. Hypokalaemia can occur due to excessive loss of potassium for example due to severe diarrhoea and vomiting. 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. If you have diabetes, your potassium concentration may fall after you take insulin, particularly if your blood glucose concentrations have been too high 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.

The way that your blood is taken and handled can affect the potassium concentration in your blood sample. If you clench or pump your fist a lot while your blood is being collected the potassium concentration in the blood may rise. If blood cells are damaged during sample collection they 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 time to travel from your GP surgery (or where you had the blood test) 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.

Treatment for hypokalaemia may include the use of potassium supplements such as Sando K and increasing the amount of potassium-rich foods in the diet, such as bananas, beef, or spinach. Treatment for hyperkalaemia is usually based on treatment of the underlying cause and may include the use of diuretics, kidney dialysis, or insulin injections.