Shrimp, as well as other invertebrate species, have extremely quick hemolymph clotting times. A non-clotted sample is optimal to effectively measure most hematological parameters. Syringes are typically coated with some form of anticoagulant prior to hemolymph collection to delay or prevent clotting long enough to allow time for such analysis to be conducted. During a recent experiment we used a commercial ly available anticoagulant, containing dipotassium ethylenediamine tetraacetate, that had been successfully used to collect hemolymph from other invertebrates for Litopenaeus vannamei; however, the hemolymph clotted too fast to be used for the intended analysis . To preserve the remaining samples, a solution of lab-made anticoagulant , containing sodium citrate, was used in place of the commercial anticoagulant . There were observable differences between the hemolymph collected with the two anticoagulants, including s ample clotting time and sample hue. The hemolymph collected with the commercial anticoagulant clotted within seconds and had a cloudy, slightly purple color, while the lab-made anticoagulant did not clot and was clear in appearance. Due to the increased clotting and the cloudy appearance of the hemolymph when using the commercial anticoagulant, it was difficult to obtain differential hemocyte counts using a hemocytometer . When using the hemolymph collected with the lab-made anticoagulant the samples were clear and the different cell types were easily distinguished under the microscope. Measuring phagocytic capacity of hemolymph collected with the commercial anticoagulant was also challenging. The sample was too thick and the unadhered hemocytes did not wash off the slides, creating a dense mound that became saturated with dye when staining , making it difficult to visualize the phagocytizing hemocytes. When using the lab-made anticoagulant , the unadhered hemocytes were readily washed away, and staining was even . This allowed for easier visualization of phagocytic activity. Due to these observable differences, the use of the commercially available anticoagulant initially used is not advocated for the collection of hemolymph from L. vannamei . Although this product may work well as an anticoagulant for some invertebrate species we recommend the use of sodium citrate for L. vannamei .