Mg vs. Meq — What's the Difference?

Mg, or milligrams, is a unit of mass used universally in both scientific and general contexts to quantify the amount of a substance. Whereas Meq, short for milliequivalents, is used specifically in chemistry and medicine to express the amount of a substance based on its chemical activity and valence.

The concept of mg is straightforward; it quantifies the actual weight of a substance, making it easy to understand and apply in everyday situations like weighing food or medication. On the other hand, Meq is more complex as it considers the number of ions in a solution and their charge, which is crucial for calculating doses in medical settings, particularly for electrolytes.

When using mg, the focus is solely on the mass, with 1,000 milligrams equaling one gram. This makes mg a suitable unit for recipes, instructions on medication, or any scenario requiring precise measurement of a substance's quantity. Whereas, Meq takes into account the equivalence of an ion’s electrical charge, important in scenarios where ionic concentration impacts the outcome, such as in intravenous fluid preparation.

The application of mg is universal across various fields, from cooking to pharmaceuticals, reflecting its versatility and ease of understanding. In contrast, Meq is predominantly used in health-related fields, particularly when balancing the electrolytic and acid-base composition in the human body.

In practical terms, mg will be used to measure how much of a substance is present, such as 500 mg of Vitamin C. Meanwhile, Meq is used to express how effective an ion will be in a chemical reaction, such as calculating the required Meq of potassium in a solution to achieve a desired concentration.