Which component is within the range of 0.8-1.5 mmol/L normally?

The correct answer is calcium. In the human body, normal serum calcium levels typically range from approximately 2.1 to 2.6 mmol/L when expressed in total calcium, but ionized calcium levels— the biologically active form—have a narrower range, which often falls between 0.8 and 1.5 mmol/L. This is crucial for various physiological functions, including muscle contraction, blood clotting, and nerve transmission.

In the context of other electrolytes mentioned, sodium levels are generally much higher, averaging around 135-145 mmol/L, while phosphorus levels typically range from 0.81 to 1.45 mmol/L and magnesium levels are usually between 0.65 and 1.05 mmol/L. Understanding these ranges helps healthcare professionals monitor and assess for imbalances that could lead to significant health issues.