BackgroundCurrent guidelines for diabetic ketoacidosis (DKA) recommend treatment with normal saline (NS). However, NS, with its high chloride concentrations, may worsen acidosis and contribute to a hyperchloremic metabolic acidosis. Alternatives to NS are balanced crystalloids (e.g. Ringer’s Lactate [RL]) which have chloride concentrations similar to human plasma; therefore, treatment with balanced crystalloids may lead to faster DKA resolution. A recent systematic review and meta-analysis by Catahay et al.(2022) demonstrated the need for more blinded, high-quality trials comparing NS versus RL in the treatment of DKA.MethodsWe describe a protocol for BRISK-ED (Balanced crystalloids [RInger’s lactate] versus normal Saline in adults with diabetic Ketoacidosis in the Emergency Department). Our study is a single-centre, triple-blind, pilot randomized controlled trial (RCT) of adults (≥ 18 years) with DKA presenting to an academic tertiary care ED in London, Canada.Patients with clinical suspicion for DKA will be screened and those found to not meet DKA criteria or have euglycemic DKA will be excluded. We will aim to recruit 52 patients with DKA and will randomize them 1:1 to receive intravenous RL or NS.The primary feasibility outcome will be recruitment rate, and the primary efficacy outcome will be time elapsed from ED presentation to DKA resolution. Secondary outcomes include time to insulin infusion discontinuation, intensive care unit admission, in-hospital death, and major adverse kidney events within 30 days, defined as a composite of: i) death, ii) new renal replacement therapy, or iii) final serum creatinine ≥ 200% baseline at the earliest of hospital discharge or 30 days after ED presentation. Patients, clinicians, and outcome assessors will be blinded to allocation group. We will follow an intention-to-treat analysis. Gehan-Wilcoxon, Mann–Whitney U, or chi-square tests will be used to compare groups as appropriate.DiscussionThe results of this pilot study will inform the design and feasibility of a full-scale, multicentre RCT to assess fluid choice in adult ED patients with DKA. If proven to demonstrate faster resolution of DKA, administration of balanced crystalloids may replace NS in diabetes treatment guidelines and improve patient and health systems outcomes.Trial registrationClinicalTrials.gov, Registration # NCT04926740; Registered June 15, 2021.Supplementary InformationThe online version contains supplementary material available at 10.1186/s40814-023-01356-5.