Potassium

Potassium testing is frequently ordered, along with other electrolytes, as part of a routine physical. It is used to detect concentrations that are too high (hyperkalemia) or too low (hypokalemia). The most common cause of hyperkalemia is kidney disease, but many drugs can decrease potassium excretion from the body and result in this condition. Hypokalemia can occur if you have diarrhea and vomiting or if you are sweating excessively. Potassium can be lost through your kidneys in urine; in rare cases, potassium may be low because you are not getting enough in your diet.

Potassium concentrations may be ordered at regular intervals to monitor drugs that can cause your kidneys to lose potassium, particularly diuretics, resulting in hypokalemia. Monitoring may also be done if you have a condition or disease, such as acute or chronic kidney failure, that can be associated with abnormal potassium levels.

serum or plasma tests for potassium levels are routinely performed in most patients when they are investigated for any type of serious illness. Also, because potassium is so important to heart function, it is usually ordered (along with other electrolytes) during all complete routine evaluations, especially in those who take diuretics or or blood pressure or heart medications. Potassium is ordered when a doctor is diagnosing and evaluating high blood pressure (hypertension) and kidney disease and when monitoring a patient receiving dialysis, diuretic therapy, or intravenous therapy.

Increased potassium levels indicate hyperkalemia. Increased levels may also indicate the following health conditions:

• acute or chronic kidney failure
• Addison's disease
• hypoaldosteronism (see Aldosterone)
• injury to tissue
• infection
• diabetes
• dehydration
• excessive dietary potassium intake (for example, fruits are particularly high in potassium, so excessive intake of fruits or juices may contribute to high potassium)
• excessive intravenous potassium intake

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

Decreased levels of potassium indicate hypokalemia. Decreased levels may occur in a number of conditions, particularly:

• dehydration
• vomiting
• diarrhea
• Hyperaldosteronism (see Aldosterone)
• deficient potassium intake (rare)
• as a complication of acetaminophen overdose

In diabetes, your potassium may fall after you take insulin, particularly if your diabetes had 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.

Additionally, 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 can cause loss of potassium.

Physicians question elevated potassium results when the numbers do not fit the patient’s clinical condition. Potassium levels can be falsely elevated by the following specimen-collection or –processing errors: