Injectable Thiamine for Acute Thiamine Deficiency and Wernicke-Korsakoff Syndrome
For suspected or confirmed Wernicke encephalopathy, administer 500 mg IV thiamine three times daily (total 1,500 mg/day) for at least 3-5 days, then transition to oral thiamine 100-500 mg daily for 12-24 weeks. 1
Indication-Based Dosing Algorithm
Established Wernicke Encephalopathy
- 500 mg IV three times daily (total 1,500 mg/day) for 3-5 days 1, 2
- This is the highest priority scenario requiring maximum dosing 1
- After initial IV course, transition to oral thiamine 100-500 mg daily for 12-24 weeks 1
Suspected Wernicke Encephalopathy or High-Risk Patients
- 200-300 mg IV daily for 3-4 days 1, 2
- High-risk includes: alcohol use disorder with malnutrition, prolonged vomiting, post-bariatric surgery, critical illness, or unexplained encephalopathy 1
- Alternative regimen: 250-300 mg IV twice daily for 3-5 days 2
Alcohol Use Disorder Without Encephalopathy
- 100-300 mg IV daily for 3-4 days if hospitalized or at high risk 1
- After IV course, continue oral thiamine 100-300 mg daily for 2-3 months 1
- For outpatients with uncomplicated alcohol dependence: oral thiamine 250-500 mg daily for 3-5 days, then 100-250 mg daily 2
Refeeding Syndrome Prevention
- 300 mg IV before initiating nutrition, then 200-300 mg IV daily for at least 3 more days 1
- This must be given before any glucose-containing fluids or parenteral nutrition 1
Route Selection: Critical Decision Points
Use IV route when:
- Any suspicion of Wernicke encephalopathy (confusion, ataxia, ophthalmoplegia) 1, 2
- Active vomiting or severe dysphagia 1
- Alcohol-related gastritis (poor GI absorption) 1
- Hospitalized or critically ill patients 1
- Before administering glucose-containing IV fluids 3, 1
Oral route acceptable when:
- Suspected chronic deficiency without acute disease 1
- Patient tolerating oral intake without vomiting 1
- Maintenance therapy after completing IV course 1
Critical Timing Considerations
Thiamine must be administered BEFORE glucose-containing IV fluids. 3, 1 Giving glucose to a thiamine-deficient patient can precipitate acute Wernicke-Korsakoff syndrome and cause irreversible brain damage 3, 1. This is a preventable complication that all emergency department staff must recognize 3.
In life-threatening hypoglycemia, give thiamine concurrently with or immediately after glucose correction, but do not delay glucose for hypoglycemia 1.
Monitoring Recommendations
Laboratory Assessment
- Measure red blood cell (RBC) or whole blood thiamine diphosphate (ThDP) if testing is performed 1
- Plasma thiamine is not useful and should not be used 1
- Do not wait for laboratory confirmation to treat—begin empiric therapy immediately in suspected cases 1
Clinical Monitoring
- Assess for resolution of confusion, ataxia, and ocular abnormalities 1
- Monitor for improvement in cardiovascular symptoms if present 1
- Check for concomitant magnesium deficiency, which impairs thiamine-dependent enzymes 1
Duration of Treatment
Acute Phase
- IV therapy: 3-5 days minimum for established or suspected Wernicke encephalopathy 1, 2
- Continue until clinical improvement is evident 1
Transition and Maintenance
- After IV course for Wernicke encephalopathy: oral thiamine 100-500 mg daily for 12-24 weeks 1
- Alcohol use disorder without encephalopathy: oral thiamine 100-300 mg daily for 2-3 months after withdrawal resolution 1
- Post-bariatric surgery: lifelong supplementation 50-100 mg daily 1
Special Populations
Post-Bariatric Surgery
- Immediate parenteral replacement: 200-300 mg IV daily for prolonged vomiting or poor intake 3, 1
- Prophylaxis: 50 mg oral once or twice daily during first 3-4 months postoperatively 1
- Lifelong maintenance: 50-100 mg oral daily due to permanent malabsorption 1
Alcohol Use Disorder
- IV route is mandatory due to impaired GI absorption from alcohol-related gastritis 1, 4
- 30-80% of alcohol-dependent individuals show thiamine deficiency 1
- The combination of thiamine deficiency and alcohol metabolism interferes with thiamine transport across the blood-brain barrier, requiring higher IV doses 4
Safety Profile
- No established upper limit for toxicity—excess thiamine is excreted in urine 1
- High IV doses (>400 mg) rarely cause anaphylaxis 1
- Doses >400 mg may induce mild nausea, anorexia, or mild ataxia 1
- The benefit-risk ratio is overwhelmingly favorable, even with empiric high-dose treatment 1
Common Pitfalls to Avoid
Inadequate Dosing
- Standard multivitamins contain only 1-3 mg thiamine, which is insufficient for treating deficiency 1
- Using 100 mg IV daily for established Wernicke encephalopathy is inadequate—500 mg three times daily is required 1
Delayed Treatment
- Do not wait for laboratory confirmation—thiamine reserves can be depleted within 20 days 1
- Irreversible neurological damage can occur within days to weeks if untreated 1
- Approximately 19% of patients develop permanent cognitive impairment even with treatment 1
Premature Discontinuation
- Discontinuing oral thiamine after completing IM/IV therapy is the most common cause of relapse 1
- Tissue stores require months to fully replenish 1
Glucose Administration Error
- Never give glucose-containing IV fluids before thiamine in at-risk patients 3, 1
- This can precipitate acute Wernicke-Korsakoff syndrome 3
Evidence Quality Note
The highest-quality and most recent guideline evidence comes from the 2026 Praxis Medical Insights compilation 1, which synthesizes recommendations from the American College of Clinical Nutrition, Clinical Nutrition Society, American Society for Metabolic and Bariatric Surgery, and European Society for Clinical Nutrition and Metabolism. The 2020 British Obesity and Metabolic Surgery Society guidelines 3 provide additional context for post-bariatric surgery patients. While prospective randomized trials are lacking, the consistent recommendations across multiple societies and the favorable benefit-risk profile support aggressive empiric treatment in suspected cases 1.