2023 Mar 18. In: StatPearls [Internet]. Treasure Island (FL): StatPearls Publishing; 2023 Jan–.
One of the most common electrolyte disturbances seen in clinical practice is hypokalemia. Hypokalemia is more prevalent than hyperkalemia; however, most cases are mild. Although there is a slight variation, an acceptable lower limit for normal serum potassium is 3.5 mmol/L. Severity is categorized as mild when the serum potassium level is 3 to 3.4 mmol/L, moderate when the serum potassium level is 2.5 to 3 mmol/L, and severe when the serum potassium level is less than 2.5 mmol/L. Values obtained from plasma and serum may differ. Therefore, it is important to know the sampling source. Compared to plasma levels, serum levels are usually slightly higher due to delays in processing and/or the effect of clotting.