What is the usual osmolality of standard infant formulas with a caloric density of 20 kcal/oz?

• A. 400-600 mOsm/kg
• B. 200-380 mOsm/kg
• C. 100-200 mOsm/kg
• D. 500-700 mOsm/kg

Answer: (B)

Osmolality is a measure of how many solute particles are in a kilogram of water, and infant formulas are designed to be tolerated by the immature gut while providing needed calories. For standard formulas at a 20 kcal/oz density, the typical osmolality falls in the mid range, about 200 to 380 mOsm/kg. This range reflects a balance of carbohydrates, proteins, fats, and minerals added to deliver energy without pushing the formula into high osmolality that can irritate the gut or cause osmotic diarrhea.

Ranging into 400–600 mOsm/kg or 500–700 mOsm/kg would place the formula at higher osmolality levels than standard products, increasing the risk of GI discomfort and diarrhea. A range of 100–200 mOsm/kg would be too low for a complete infant formula, which must supply a full set of nutrients. Thus, 200–380 mOsm/kg best represents the usual osmolality for standard 20 kcal/oz infant formulas.