What does the evidence show about Vitamin B1 (thiamine)'s effects?

Read Off Label rates the evidence for Vitamin B1 (thiamine) as Strong and the benefit magnitude as high, producing an overall grade of A+ (8.4/10). Diuretics, alcohol, glucose loads, and bariatric surgery deplete thiamine fast.

What safety findings are reported for Vitamin B1 (thiamine)?

Vitamin B1 (thiamine) has a low risk profile in the database. Low Legal status: OTC; Rx (IV/IM for Wernicke).

What doses or routes are reported for Vitamin B1 (thiamine)?

1.1-1.2 mg/day RDA; 50-100 mg/day for at-risk groups (alcohol use, bariatric surgery, hyperemesis); benfotiamine 150-600 mg/day for diabetic neuropathy This is context from studies, approved labeling, clinical practice, or documented use; it is not individualized guidance and does not establish safety.

Rankings / Essentials — Vitamins & Minerals

Vitamin B1 (thiamine)

Essentials · Vitamin

Tier A+

Reviewed by Read Off Label · Last reviewed Jun 8, 2026 · How we grade

vitaminmitochondrialotc

8.4 / 10

Tier A+

Ev 8 Bn 8 Sf 9

Bottom line

Read Off Label grades Vitamin B1 (thiamine) as A+ (8.4/10) based on strong evidence, high benefit magnitude, and a low-risk safety profile.

Diuretics, alcohol, glucose loads, and bariatric surgery deplete thiamine fast.

Studied, labeled, or reported-use context: 1. — OTC; Rx; not individualized guidance.

What the evidence says

Diuretics, alcohol, glucose loads, and bariatric surgery deplete thiamine fast. Empirical IV thiamine before any glucose load in suspected refeeding/alcoholic encephalopathy is standard ICU practice. Benfotiamine (lipid-soluble analog) has better tissue penetration and is the form used in diabetic neuropathy trials.

Mechanism

Cofactor for pyruvate dehydrogenase, alpha-ketoglutarate dehydrogenase, transketolase — central to glucose oxidation and the pentose phosphate pathway; required for branched-chain amino acid metabolism

Studied, labeled, or reported dose & route

1.1-1.2 mg/day RDA; 50-100 mg/day for at-risk groups (alcohol use, bariatric surgery, hyperemesis); benfotiamine 150-600 mg/day for diabetic neuropathy

This records doses and routes described in studies, approved labeling, clinical practice, or documented use. It is not individualized guidance and does not establish safety; context changes with indication, formulation, health history, monitoring, and other medicines.

Citations

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Common questions

What does the evidence show about Vitamin B1 (thiamine)'s effects?: Read Off Label rates the evidence for Vitamin B1 (thiamine) as Strong and the benefit magnitude as high, producing an overall grade of A+ (8.4/10). Diuretics, alcohol, glucose loads, and bariatric surgery deplete thiamine fast.
What safety findings are reported for Vitamin B1 (thiamine)?: Vitamin B1 (thiamine) has a low risk profile in the database. Low Legal status: OTC; Rx (IV/IM for Wernicke).
What doses or routes are reported for Vitamin B1 (thiamine)?: 1.1-1.2 mg/day RDA; 50-100 mg/day for at-risk groups (alcohol use, bariatric surgery, hyperemesis); benfotiamine 150-600 mg/day for diabetic neuropathy This is context from studies, approved labeling, clinical practice, or documented use; it is not individualized guidance and does not establish safety.
How does Vitamin B1 (thiamine) work?: Cofactor for pyruvate dehydrogenase, alpha-ketoglutarate dehydrogenase, transketolase — central to glucose oxidation and the pentose phosphate pathway; required for branched-chain amino acid metabolism

This is an independent synthesis of published research by a non-clinician. Scores are opinions supported by citations, not prescriptions. See the full disclaimer and methodology for how this score was produced and what it does and doesn't mean.