“Thiamine before glucose” is a bedside teaching that started with a sound physiologic concept and slowly hardened into dogma when dealing with patients with alcohol use disorder.
Thiamine deficiency underlies Wernicke encephalopathy, a preventable but often missed neurologic emergency most commonly seen in alcohol use disorder, malnutrition, prolonged vomiting, and after bariatric surgery. The concern with glucose is biologically plausible. Thiamine is a required cofactor for key steps in aerobic glucose metabolism, and deficiency shifts the brain toward energy failure, lactate accumulation, and oxidative stress. In a thiamine-depleted brain, sustained carbohydrate exposure without replacement can worsen injury.
Traditional teaching insists on strict sequencing, but the clinical evidence does not. The American Society of Addiction Medicine explicitly states that thiamine does not need to be given before glucose and that both can be administered in any order or concurrently to avoid delays in care. Furthermore, a national cohort study of veterans who received dextrose before thiamine found no cases of Wernicke encephalopathy, and a systematic review reached the same conclusion, noting that the supposed risk is supported only by case reports rather than higher-quality clinical data. The feared scenario appears to involve prolonged glucose administration without thiamine, not a single lifesaving bolus of dextrose.
So in general, never delay glucose for hypoglycemia, but never miss the opportunity to give thiamine when the story fits. That approach respects physiology, evidence, and urgency simultaneously.
Here are some PubMed IDs to review the data: 32511109, 9486750, 22104258, 20642790, 12414541, 40873301
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