Despite the adoption of metric units in US hospitals, dissolved substances are variously measured in milligrams per deciliter, “grams percent,” 1:200,000, and so forth. Sodium, for example, is reported in milliequivalents per liter in the serum, but administered intravenously as a “quarter normal” solution, “0.45% solution,” and so forth. If SI were fully adopted, a resident could anticipate the effect of giving a solution labeled “sodium chloride 154 mmol/L” to a patient with a serum sodium of 110 mmol/L (110 mEq/L) without the need to recall the molecular weight of the elements or figure out the meaning of “0.9% NaCl” or “normal saline.” The resident may recall the chemical term “normal,” which refers to a solution containing an “equivalent weight” of solute (the amount that would react with a mole of other ions). Because normal saline contains 154 mmol NaCl, it is chemically a 0.154 normal solution (assuming complete dissociation). SI would avoid the confusing term “normal” in either the physiologic or the chemical sense.