BACKGROUND: The impact of site selection on blood sampling and catheter functionality for long peripheral catheters (LPCs) is unclear. PURPOSE: To compare outcomes of LPCs placed in the upper arm vs the forearm. METHODS: A single-site, randomized trial was conducted among adult patients requiring an LPC for difficult venous access or prolonged therapy. Participants were randomized to receive an 8 cm, 20-gauge LPC in either the forearm or upper arm. Outcomes included blood sampling success, catheter survival, and catheter-associated thrombosis. RESULTS: Among 88 patients, blood sampling failure was common, with no significant difference between forearm (83.3%) and upper arm (78.1%) groups (P = .769). Mean dwell time (74.27 vs 115.52 hours, P = .394) and time to first blood sampling failure (70.19 vs 112.90 hours, P = .359) were similar. While overall blood sampling success and thrombosis rates did not differ, trends favored upper arm placement over time. CONCLUSIONS: This study found no statistically significant differences in blood sampling capability or functionality between placement sites.