In cases of ethylene glycol (EG) toxicity requiring hemodialysis (HD), fomepizole is dosed every four hours. HD efficiently clears EG and its toxic metabolites, and it's unclear if multiple doses (MD) of fomepizole improve patient outcomes or whether a single dose (SD) prior to initiation of HD is sufficient.We reviewed cases of EG toxicity at a toxicology referral center from 2008 to 2018. Patients treated with HD with EG levels greater than 20 mg/dL were included. Duration of dialysis, creatinine at discharge, hospital length of stay (LOS), and complications were analyzed. We compared patients who received a single dose of fomepizole prior to HD to those who received continued dosing during and after HD.Twenty-five patient encounters were identified (MD: 20; SD: 5). Initial bicarbonate (11 [SD] vs. 9 mg/dL [MD]) and pH (7.1 vs. 7.1) were similar between the groups; however, there was a trend toward a greater proportion of patients with renal dysfunction in the MD group: 11 (55%) vs. 1 (20%). HD was initiated a median interval of 5.2 h [SD] vs. 5.7 h [MD] after a dose of fomepizole. There was one death in the MD group and none in the SD group. Median creatinine on the day of discharge was 0.7 mg/dL (IQR: 0.57-3.8) in the SD group and 2.0 mg/dL (0.90-7.0) in the MD group. LOS was similar (5.8 days [95% CI 3.6-8.0] vs. 7.6 days [5.3-9.9]) ( = .61).Patients with moderately severe EG toxicity (acidosis and no initial renal dysfunction) treated with a single dose of fomepizole prior to HD had similar outcomes to those receiving continued dosing of fomepizole during or after HD. This raises the possibility that a single dose of fomepizole may be sufficient if HD is initiated quickly.