Clinical Laboratory Science Practice Exam

In electrolyte testing, the ions should generally align within typical physiological ranges, and a sodium result that sits outside its normal range while the other electrolytes remain within normal limits often points to a measurement artifact rather than a true physiologic change. Sodium normally runs about 135–145 mEq/L. Chloride and bicarbonate usually fall in narrow ranges as well, and you’d expect a real hypernatremia to be accompanied by corresponding shifts in other electrolytes or a clear clinical picture.

Looking at the first set: sodium is 149, while chloride is 102 and bicarbonate is 26. The chloride and bicarbonate are comfortably within their normal ranges, and the sodium value is only mildly elevated. This pattern is the most suspicious for a potential sodium measurement error, because you’d expect some accompanying electrolyte pattern or clinical context if the hypernatremia were real. The other options show slightly higher sodium values, but the accompanying chloride and bicarbonate values don’t provide a clearer physiologic justification that would override the possibility of an analytic issue.

Therefore, the best indication of a potential problem with the sodium measurement is the first panel, where sodium is modestly elevated with normal chloride and bicarbonate. In practice, the next step would be to repeat the sodium measurement on a new sample to confirm.