Thiamine Dosing Recommendations
For acute thiamine deficiency or high-risk situations (hospitalized patients, critical illness, suspected Wernicke encephalopathy), administer 100-300 mg IV daily, escalating to 500 mg IV three times daily if Wernicke encephalopathy is established or strongly suspected. 1
Dosing Algorithm by Clinical Scenario
Emergency/High-Risk Situations
- Established Wernicke encephalopathy: 500 mg IV three times daily for 3-5 days 1, 2
- Suspected Wernicke encephalopathy or encephalopathy of uncertain etiology: 500 mg IV three times daily 1
- Emergency/ICU patients: 100-300 mg IV daily for 3-4 days from admission 1
- Refeeding syndrome: 300 mg IV before initiating nutrition, then 200-300 mg IV daily for at least 3 more days 1
- Critically ill patients: Loading dose of 50-250 mg on ICU admission 3
Alcohol-Related Conditions
- Alcoholic liver disease with withdrawal: 100-300 mg/day IV for 2-3 months 1
- Alcohol dependence with suspected deficiency: 250-300 mg IV twice daily for 3-5 days, followed by oral 250-300 mg/day 4
- Uncomplicated alcohol dependence (low risk): Oral 250-500 mg/day for 3-5 days, then 100-250 mg/day 4
Moderate Risk Situations
- Chronic diuretic therapy: 50 mg/day orally 1
- Continuous renal replacement therapy: 100 mg/day 1
- Bariatric surgery with prolonged vomiting/dysphagia: 200-300 mg daily orally 1
Mild Deficiency
- Initial treatment: 10 mg/day orally for one week 1
- Maintenance: 3-5 mg/day orally for at least 6 weeks 1
- After proven deficiency: 50-100 mg/day orally 1
Specific Conditions
- "Wet" beriberi with myocardial failure: 10-20 mg IM three times daily for up to two weeks (emergency cardiac condition requiring slow IV administration) 2
- Infantile beriberi with collapse: 25 mg IV cautiously 2
- Neuritis of pregnancy with severe vomiting: 5-10 mg IM daily 2
Route of Administration Decision Tree
IV route is mandatory for:
- Acute disease or suspected inadequate intake 1
- Alcohol-related gastritis (poor oral absorption) 1
- Any patient receiving glucose-containing IV fluids (give thiamine first to avoid precipitating acute deficiency) 1
- Suspected or established Wernicke encephalopathy 1, 2
Oral route is adequate for:
- Suspected chronic deficiency without acute disease 1
- Maintenance therapy after initial IV treatment 1
- Low-risk patients with uncomplicated deficiency 4
Critical Timing Considerations
Thiamine must be administered BEFORE glucose-containing IV fluids to avoid precipitating acute thiamine deficiency or heart failure 1, 2. For patients with marginal thiamine status receiving dextrose, give 100 mg thiamine in each of the first few liters of IV fluid 2.
Never delay treatment waiting for laboratory confirmation—thiamine reserves can be depleted within 20 days of inadequate intake 1. The mortality rate for untreated Wernicke-Korsakoff syndrome is approximately 20% 5.
Infusion Rate Considerations
Slower infusions may be superior to rapid bolus injections. When 150 mg thiamine was given over 24 hours versus 1 hour, urinary excretion decreased from 83.6% to 57.6%, suggesting increased tissue uptake with slower administration 6. For "wet" beriberi with myocardial failure, thiamine must be administered slowly by IV route 2.
Common Pitfalls to Avoid
- Underdosing in Wernicke encephalopathy: Do not use doses lower than 500 mg three times daily for established or suspected Wernicke encephalopathy—lower doses are inadequate for acute neurological presentations 1
- Wrong laboratory test: Plasma thiamine measurement is not useful; measure RBC or whole blood thiamine diphosphate (ThDP) if laboratory confirmation is needed 1
- Delaying treatment: Treatment should never be delayed for laboratory confirmation in high-risk scenarios 1
- Forgetting glucose interaction: Always give thiamine before glucose-containing fluids 1, 2
Safety Profile
Thiamine has no established upper limit for toxicity, with excess excreted in urine 1. The risk of anaphylactic shock from parenteral thiamine is below 1 in 100,000 5. High IV doses rarely cause anaphylaxis; doses exceeding 400 mg may induce mild nausea, anorexia, and mild ataxia 1. Oral thiamine is safe at all recommended doses 5.