What is the recommended treatment for vitamin B1 (Thiamine) deficiency?

Treatment of Vitamin B1 (Thiamine) Deficiency

For suspected or confirmed thiamine deficiency, immediately administer parenteral thiamine 100-300 mg IV daily, with escalation to 500 mg IV three times daily if Wernicke's encephalopathy is suspected, followed by oral maintenance therapy of 100-300 mg daily. 1, 2

Acute/High-Risk Treatment Algorithm

Immediate IV Therapy (First-Line for Acute Deficiency)

When to use IV route:

• Suspected Wernicke's encephalopathy (confusion, ataxia, ophthalmoplegia) 1, 2
• Prolonged vomiting, dysphagia, or inability to tolerate oral supplements 3
• Alcohol dependence with neurological symptoms 1, 4
• Hospitalized/critically ill patients 1
• Refeeding syndrome risk 1
• Poor gastrointestinal absorption (alcohol-related gastritis, post-bariatric surgery) 1

Dosing by severity:

• Established Wernicke's encephalopathy: 500 mg IV three times daily for 3-5 days, then transition to oral 250-1000 mg daily 1, 2, 4
• Suspected Wernicke's or high-risk patients: 100-300 mg IV daily for 3-4 days 1, 2
• "Wet" beriberi with cardiac failure: Administer slowly IV as emergency cardiac treatment 2
• Refeeding syndrome prevention: 300 mg IV before initiating nutrition, then 200-300 mg IV daily for at least 3 more days 1

Oral Therapy (For Mild/Chronic Deficiency)

When oral route is appropriate:

• Suspected chronic deficiency without acute neurological symptoms 1
• Uncomplicated alcohol dependence without encephalopathy 4
• Post-bariatric surgery prophylaxis 3

Dosing:

• Mild deficiency: 10 mg daily for one week, then 3-5 mg daily for at least 6 weeks 1
• Maintenance after proven deficiency: 50-100 mg daily 1
• Uncomplicated alcohol dependence: 250-500 mg daily for 3-5 days, then 100-250 mg daily 4
• Post-bariatric surgery with risk factors: 200-300 mg daily 3, 5

Critical Timing Considerations

Thiamine must be administered BEFORE glucose-containing IV fluids to avoid precipitating acute thiamine deficiency. 1, 6 This is a common and dangerous pitfall—patients receiving dextrose infusions should receive 100 mg thiamine in the first few liters of IV fluid. 2

Never delay treatment waiting for laboratory confirmation. 6 Thiamine reserves can be depleted within 20 days of inadequate intake, and the consequences of untreated deficiency (Wernicke's encephalopathy, cardiac failure) far outweigh any risks of treatment. 1, 7

Special Populations

Alcohol Dependence

• 30-80% of alcohol-dependent individuals show thiamine deficiency 1
• IV route is strongly preferred due to poor gastrointestinal absorption 1, 4
• For established Wernicke's: 200-500 mg IV three times daily for 3-5 days 4
• For suspected Wernicke's: 250-300 mg IV twice daily for 3-5 days 4
• Continue oral supplementation 250-1000 mg daily after IV course 4

Post-Bariatric Surgery

• High-risk period is first 3-4 months postoperatively 3
• Standard multivitamin containing thiamine may be insufficient 3
• Consider additional thiamine 50 mg once or twice daily from B-complex supplement 3
• If prolonged vomiting, poor intake, or fast weight loss: immediate parenteral replacement 200-300 mg daily 3, 5

Pregnancy with Severe Vomiting

• 5-10 mg IM daily if vomiting precludes oral therapy 2

Infantile Beriberi

• Mild cases may respond to oral therapy 2
• If collapse occurs: 25 mg IV cautiously 2

Duration of Treatment

• Acute deficiency with IV therapy: 3-5 days IV, then transition to oral 1, 4
• Mild deficiency: Minimum 6 weeks of oral therapy 1
• Alcoholic liver disease: 2-3 months following resolution of withdrawal symptoms 1
• Post-bariatric surgery prophylaxis: First 3-4 months postoperatively 3

Safety Profile

Thiamine has an exceptionally favorable safety profile with no established upper limit for toxicity. 1, 5 Excess thiamine is excreted in urine. 1, 5 High IV doses rarely cause anaphylaxis, and doses exceeding 400 mg may induce only mild nausea, anorexia, and mild ataxia. 1, 6, 5 The benefit-risk ratio for prophylactic thiamine is highly favorable, even with limited evidence. 1

Monitoring

Laboratory assessment:

• Red blood cell (RBC) or whole blood thiamine diphosphate (ThDP) is the preferred biomarker 1, 6
• Plasma thiamine measurement is not useful 6
• Erythrocyte transketolase activity is an alternative functional assay 1

Clinical monitoring is recommended for:

• Suspected deficiency with cardiomyopathy 1
• Prolonged diuretic treatment 1
• Prolonged medical nutrition 1
• Post-bariatric surgery patients 1
• Refeeding syndrome 1
• Encephalopathy of uncertain etiology 1

Common Pitfalls to Avoid

1. Do not use low oral doses (e.g., 10 mg) for suspected Wernicke's encephalopathy—this is grossly inadequate for acute neurological presentations 6
2. Do not give glucose before thiamine in at-risk patients 1, 6, 2
3. Do not rely on oral absorption in alcohol-dependent patients with acute symptoms 1, 4
4. Do not wait for laboratory confirmation before treating suspected deficiency 6
5. Do not assume standard multivitamins are sufficient in high-risk populations like post-bariatric surgery patients 3