In the absence of recent international recommendations supported by scientific societies like Anesthesiology or Intensive Care Medicine, healthcare professionals (HCP) knowledge on IV fluid is expected to vary. We undertook a cross-sectional survey, aiming to assess prescription patterns and test the knowledge of HCP for IV fluid use in the operating room (OR) and intensive care unit (ICU). An online international cross-sectional survey was conducted between October 20, 2019, and November 27, 2021. The survey included multiple-choice questions on demographics, practice patterns and knowledge of IV fluids, and a hemodynamically unstable patient assessment. 1045 HCP, from 97 countries responded to the survey. Nearly three-quarters reported the non-existence of internal hospital or ICU-based guidelines on IV fluids. The respondents' mean score on the knowledge assessment questions was 46.4 ± 14.4. The cumulative mean scores were significantly higher among those supervising trainees (p = 0.02), specialists (p < 0.001) and those working in high-income (p < 0.001) countries. Overall performance of respondents on the knowledge testing for IV fluid was unsatisfactory with only 6.5% respondents performed above average. There is a wide difference in the knowledge and prescription of IV fluids among the HCP surveyed. These findings reflect the urgent need for education on IV fluids.