What is the recommended dose of thiamine (Vitamin B1)?

Recommended Thiamine (Vitamin B1) Dosing

The recommended thiamine dosage varies by clinical scenario, with maintenance doses of 50-100 mg/day orally for proven deficiency, while acute conditions like Wernicke encephalopathy require 500 mg IV three times daily for 3-5 days. 1, 2

Standard Dosing Recommendations

Preventive/Maintenance Dosing

• Standard nutritional supplementation:
  • Enteral nutrition: 1.5-3 mg/day (for patients receiving 1500 kcal/day) 1
  • Parenteral nutrition: At least 2.5 mg/day 1
• Maintenance dose for proven deficiency: 50-100 mg/day orally 1, 2
• Mild deficiency/depletion: 10 mg/day orally for one week 1

Therapeutic Dosing for At-Risk Patients

• Hospitalized patients/critical illness: 100-300 mg/day IV 1
• Refeeding syndrome: 300 mg IV before initiating nutrition therapy, followed by 200-300 mg IV daily for at least 3 more days 1
• Continuous renal replacement therapy: 100 mg/day 1
• Patients at risk of deficiency (reduced food intake, high alcohol consumption): 100-300 mg/day oral or IV 1

Therapeutic Dosing for Suspected/Confirmed Deficiency

• Wernicke encephalopathy:
  • 500 mg IV three times daily for 3-5 days, followed by 250 mg IV daily for at least 3-5 additional days 2, 3
  • Alternative regimen: 100 mg initially, followed by 50-100 mg IM daily until regular diet is consumed 3
• High suspicion or proven deficiency: 200 mg three times daily IV 2
• "Wet" beriberi with myocardial failure: 10-20 mg IM three times daily for up to two weeks 3
• Neuritis of pregnancy with severe vomiting: 5-10 mg IM daily 3

Special Clinical Scenarios

Alcoholic Patients

• Low risk (uncomplicated alcohol dependence): 250-500 mg/day oral for 3-5 days, followed by 100-250 mg/day oral 4
• High risk of thiamine deficiency: 250-500 mg/day parenteral for 3-5 days, followed by 250-300 mg/day oral 4
• Suspected Wernicke encephalopathy: 250-300 mg parenteral twice daily for 3-5 days, followed by 250-300 mg/day oral 4
• Established Wernicke encephalopathy: 200-500 mg parenteral three times daily for 3-5 days, followed by 250-1000 mg/day oral 4

Patients Receiving Dextrose

• Before dextrose administration: 100 mg IV thiamine in each of the first few liters of IV fluid to avoid precipitating heart failure 3

Important Clinical Considerations

• Thiamine should always be administered before initiating nutritional support in at-risk patients 2
• For acute conditions, IV route is preferred for maximum efficacy 1, 2
• Oral route is adequate for chronic deficiency without acute disease 1
• No upper limit for toxicity has been established; excess is excreted in urine 1
• High IV doses have rarely led to anaphylaxis 1
• Doses exceeding 400 mg may cause nausea, anorexia, and mild ataxia 1

Monitoring

• Thiamine status should be determined by measuring RBC or whole blood thiamine diphosphate (ThDP) 1
• Consider thiamine assessment in patients with:
  • Cardiomyopathy with prolonged diuretic treatment
  • Prolonged medical nutrition or post-bariatric surgery
  • Refeeding syndrome
  • Encephalopathy 1

High-dose thiamine (≥500 mg) appears safe and effective for patients with suspected Wernicke encephalopathy, with studies showing symptom improvement in approximately 73% of patients 5. Early treatment is critical to prevent progression to irreversible Korsakoff syndrome 6.