From the Guidelines
Yes, mmol and mEq can be considered the same for monovalent ions like potassium, as 1 mmol/L is equivalent to 1 mEq/L, as stated in the expert consensus document on the management of hyperkalaemia 1. When considering the measurement of potassium levels in the body, it's essential to understand the units used.
- A millimole (mmol) represents the amount of a substance containing a specific number of molecules, while a milliequivalent (mEq) represents the chemical combining or reacting power of a substance, taking into account its valence or charge.
- For monovalent ions like potassium (K⁺), the number of millimoles is equal to the number of milliequivalents, as these ions have a single charge.
- The study 1 mentions that hyperkalaemia is defined as serum or plasma K+ > 5 mmol/L, and also states that 1 mmol/L = 1 mEq/L, highlighting the equivalence of these units for potassium.
- This equivalence is crucial in clinical practice, particularly when interpreting laboratory values and calculating electrolyte replacement, to ensure proper patient care and avoid dosing errors.
- The distinction between mmol and mEq becomes significant for divalent ions, but for potassium, the two units can be used interchangeably, as supported by the expert consensus document 1.
From the Research
Definition of mmol and meq
- mmol (millimole) is a unit of measurement for the amount of a substance, typically used to express the concentration of a solution.
- meq (milliequivalent) is a unit of measurement for the amount of a substance that can combine with or replace a certain amount of another substance, typically used to express the concentration of ions in a solution.
Relationship between mmol and meq
- The relationship between mmol and meq depends on the valence of the ion being measured. For monovalent ions (e.g. sodium, potassium), 1 mmol is equal to 1 meq.
- For divalent ions (e.g. calcium, magnesium), 1 mmol is equal to 2 meq.
- In the study 2, hyponatremia is defined by a serum sodium level of less than 135 mEq/L, which is equivalent to less than 135 mmol/L for sodium, a monovalent ion.
Use of mmol and meq in clinical practice
- Both mmol and meq are used in clinical practice to express the concentration of electrolytes in the blood, as seen in the studies 3, 4, and 5.
- The study 6 discusses the use of the anion gap, which is calculated using the concentrations of ions in mmol/L, to diagnose and evaluate metabolic acidosis.
Conversion between mmol and meq
- To convert between mmol and meq, the valence of the ion must be known. For example, to convert mmol of calcium to meq, multiply the number of mmol by 2, since calcium is a divalent ion.
- The study 4 discusses the reference range for serum magnesium in mmol/L, and also provides the equivalent range in mg/dL.