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.
Blood potassium concentrations are routinely measured as part of 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.
excessive intravenous potassium intake (in patients on a drip)
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:
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.
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.
This article was last reviewed on 17 February 2012. | This article was last modified on 24 October 2013.
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