Potassium is a mineral that is vital for muscle contraction and conduction of nerve impulses. It is also involved in cell wall function and the formation and function of enzymes. Potassium (the chemical symbol is K) is balanced against sodium in the body – as one rises the other falls. Changes in the level of potassium can affect heart muscle function and the rate at which impulses are conducted in nerves. Potassium is lost from the body through the kidneys and colon; but it is readily absorbed from the gut. Bananas and apricots are both good dietary sources of potassium.
The amount of potassium in the blood can be easily measured. The normal range is between 3.5 and 5.2 mmol/L. High levels may be found in kidney failure, Addison’s disease, after massive trauma, severe infections and with very vigorous exercise. Medications such as digoxin, ACE inhibitors, NSAIDs, triamterene, amiloride and spironolactone may also be responsible. Extremely high levels may be reduced by using the medication polystyrene sulfonate.
Low levels of blood potassium may be due to vomiting, diarrhoea, ulcerative colitis, malabsorption syndromes, excessive laxatives, diabetes mellitus, Conn syndrome, Cushing syndrome, dietary deficiency and as a side effect of medications such as diuretics, steroids, laxatives, insulin and sympathomimetics.
The amount of potassium in urine can also be measured. The normal range is 30 to 90 mmol/day. Higher levels occur with diuretic (fluid tablet) therapy and excess potassium intake.