Consistent Pseudohyperkalemia due to Handgrip with a Discrepancy between the Serum and Whole Blood Potassium Levels

A 70-year-old woman consistently showed elevated serum potassium levels, whereas her whole blood potassium levels, as determined by a blood gas analysis, were within the normal range. This discrepancy was caused by handgrip-induced pseudohyperkalemia. This case highlights three important clinical aspects. First, pseudohyperkalemia should be considered in cases of asymptomatic hyperkalemia without any apparent cause. Second, handgrip or fist clenching may consistently elevate potassium levels. Finally, pseudohyperkalemia due to handgrip or fist clenching tends to elevate potassium levels, particularly in the first-drawn sample, which can result in a discrepancy between the serum and whole blood potassium levels.