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

Thiamine Dosing Recommendations

Thiamine dosing depends critically on clinical context: for healthy adults, 1.1-1.2 mg/day orally is adequate; for mild deficiency, 10 mg/day orally; for acute high-risk situations including Wernicke encephalopathy, 500 mg IV three times daily (1,500 mg/day total); and for most hospitalized patients at risk, 100-300 mg IV daily. 1

Baseline Requirements for Healthy Individuals

• Healthy adults require 1.1-1.2 mg/day orally (RDA), with an estimated average requirement (EAR) of 0.9-1.0 mg/day 2, 1
• Children and teenagers need 0.7-1.2 mg/day (EAR), with RDAs of 0.9-1.2 mg/day 2, 1
• Preterm and term infants on parenteral nutrition require 0.35-0.50 mg/kg/day 1

Parenteral Nutrition Maintenance

• Standard parenteral nutrition formulations contain 2-6 mg/day thiamine, with most European preparations containing 2.5-3.5 mg 2
• ASPEN recommends 6 mg/day to accommodate patients receiving high-dose glucose who may have very high requirements 2, 1
• This 3 mg dose in standard multivitamin preparations is adequate to maintain normal thiamine status even in patients with compromised intestinal absorption 3

Mild Deficiency (Oral Route)

For suspected chronic deficiency without acute disease, oral administration is adequate: 1

• 10 mg/day orally for one week, followed by 3-5 mg/day orally for at least 6 weeks 1
• Alternative regimen: 10-20 mg IM three times daily for up to two weeks, followed by oral multivitamin with 5-10 mg thiamine daily for one month 4
• Maintenance after proven deficiency: 50-100 mg/day orally 1

Moderate Risk Situations (Oral Route)

• Chronic diuretic therapy: 50 mg/day orally 1
• Post-bariatric surgery prophylaxis: 50 mg once or twice daily from B-complex supplement for first 3-4 months postoperatively 1
• Uncomplicated alcohol dependence (low risk): 250-500 mg/day orally for 3-5 days, then 100-250 mg/day 5

High-Risk/Acute Situations (IV Route)

The IV route is mandatory for acute disease, suspected inadequate intake, alcohol-related gastritis (poor absorption), active vomiting, or any suspicion of Wernicke encephalopathy: 1

Hospitalized/Critical Illness

• 100-300 mg/day IV for general high-risk hospitalized patients 1
• 100-300 mg/day IV for 3-4 days from admission for emergency/intensive care patients 1
• Continuous renal replacement therapy: 100 mg/day 1

Alcohol Use Disorder

• Routine alcohol withdrawal: 100 mg/day orally for all patients, continuing for 2-3 months after withdrawal resolution 1
• High-risk patients (malnourished, severe withdrawal): 100-300 mg/day IV 1
• Suspected Wernicke encephalopathy in alcohol use disorder: 250-300 mg IV twice daily for 3-5 days 5

Wernicke Encephalopathy (Established Diagnosis)

• 500 mg IV three times daily (1,500 mg/day total) for encephalopathy of uncertain etiology including Wernicke encephalopathy 1, 4
• Continue for 3-5 days, then transition to oral thiamine 250-1,000 mg/day 5
• High-dose thiamine (≥500 mg) appears safe and efficacious, with 73% of patients showing symptom resolution or improvement 6

Refeeding Syndrome

• 300 mg IV before initiating nutrition therapy, then 200-300 mg IV daily for at least 3 more days 1

Post-Bariatric Surgery with Complications

• Prolonged vomiting, dysphagia, poor intake, or fast weight loss: 200-300 mg daily IV immediately 1
• Neurological symptoms require immediate supplementation 1

Critical Timing Consideration

Thiamine must be administered BEFORE any glucose-containing IV fluids to prevent precipitating acute Wernicke encephalopathy, as thiamine is essential for glucose metabolism 1, 4

• Patients with marginal thiamine status receiving dextrose should receive 100 mg thiamine in each of the first few liters of IV fluid 4

Special Clinical Scenarios

"Wet" Beriberi with Myocardial Failure

• Must be treated as emergency cardiac condition with slow IV administration 4
• 10-20 mg IM three times daily for up to two weeks 4

Neuritis of Pregnancy

• 5-10 mg IM daily when vomiting precludes oral therapy 4

Infantile Beriberi

• Mild cases may respond to oral therapy 4
• If collapse occurs: 25 mg IV cautiously 4

Safety and Monitoring

• No established upper limit for toxicity; excess thiamine is excreted in urine 1
• High IV doses rarely cause anaphylaxis 1
• Doses >400 mg may induce nausea, anorexia, and mild ataxia 1
• Preferred biomarker: RBC or whole blood thiamine diphosphate (ThDP), as it is not affected by inflammation 1
• Monitoring recommended in suspected deficiency with cardiomyopathy, prolonged diuretic treatment, prolonged medical nutrition, post-bariatric surgery, refeeding syndrome, or encephalopathy 1

Common Pitfalls to Avoid

Guideline-concordant thiamine supplementation is rare in clinical practice, with only 2.1% of patients with encephalopathy receiving dosing consistent with Royal College of Physicians guidelines 7. The traditional 100 mg daily dosing for Wernicke encephalopathy is inadequate; updated guidelines recommend much higher doses (500 mg three times daily) 1, 6. However, some evidence suggests even a single 100 mg dose may be biologically sufficient, though clinical protocols recommend higher doses for safety 8.