OBJECTIVES:  To compare drug utilization estimates by different measurement units – Eaches, Extended Units and Kilograms – using aggregated sales data for intravenous (IV) iron products. METHODS:  We conducted a cross-sectional study using IMS Health National Sales Perspectives database (2014) to evaluate the utilization of IV iron products using three measurement units: 1) Eaches – number of vials sold, 2) Extended Units – amount of volume sold in milliliters; 3) Kilograms – amount of active ingredient sold in kilograms. The use of each IV iron product was calculated as a proportion of the number of Eaches/Extended Units/Kilograms of each IV iron product as the numerator with the total number of Eaches/Extended Units/Kilograms of all IV iron products as the denominator. RESULTS:  The utilization patterns varied by measurement units. Irrespective of the measure used, iron sucrose and ferric gluconate were the first and second most sold products, and ferric carboxymaltose was the least sold product. The ranks of the proportion of sales of ferumoxytol and iron dextran differed by measurement unit. The ranking of sales for iron dextran and ferumoxytol remained the same (third and fourth respectively) for the Eaches and Kilogram units. However, the estimated proportion of sales of iron dextran in Extended Units (4.06%) ranked lower than the estimate for ferumoxytol in Extended Units (5.29%). The estimated proportion of sales of ferumoxytol in Eaches (1.25%) was only one fourth of the estimate in Extended Units (5.29%) and one sixth of the estimate in Kilograms (7.58%). Similarly, the estimated proportion of sales of ferric carboxymaltose in Eaches (0.31%) was approximately one fourth of the estimate in Extended Units (1.26%) and one tenth of the estimate in Kilograms (3.03%). CONCLUSIONS:  Estimates of drug utilization using aggregated sales data largely depend on the measurement unit selection, as well as the characteristics of the product in consideration.