What does mEq stand for?

• A. milliequivilent
• B. millilitre
• C. gram
• D. drop(s)

Answer: (A)

The term mEq stands for milliequivalent. The “milli-” prefix means one-thousandth, and an equivalent is the amount of a substance that can supply or react with one mole of charge (such as 1 mole of H+ or 1 mole of electrons in redox chemistry). In practical terms, mEq reflects reactive capacity, not mass. So mEq equals mmol multiplied by the ion’s valence (charge). For a monovalent ion like Na+ or K+, 1 mEq equals 1 mmol. For a divalent ion like Ca2+, 1 mEq equals 0.5 mmol. This helps standardize dosing of electrolytes because ions with different charges contribute different amounts of reactive capacity even if their masses are similar. It’s not a measure of volume or weight, but of chemical activity.