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Vitamin B1 (Thiamin) — The Complete Supplement Guide

The energy-and-nerve vitamin depleted by alcohol — from beriberi to Wernicke's. Forms (including benfotiamine), deficiency and doses.

Reviewed by Bodil Isaksson, Licensed Biomedical Scientist (Sweden)Last reviewed July 2026Supplement guide

SupplementsVitaminsB1 ThiaminWater-soluble

The B vitamin most closely tied to heavy alcohol use, where deficiency is the classic cause of the neurological condition beriberi. For the short dietary version, see the Vitamins page.

Read first. Thiamin is very safe, but suspected deficiency in a heavy drinker (confusion, unsteadiness) is a medical emergency needing high-dose thiamin before glucose. Information, not a prescription.

Key takeaways

  • Deficiency is classically tied to heavy alcohol use (the cause of beriberi).
  • Adults need ≈ 1.1–1.2 mg/day.
  • No upper limit set — surplus is simply excreted.

Function

Thiamin is a coenzyme central to energy and nerves:

  • Energy from carbohydrate: a coenzyme for pyruvate dehydrogenase and other enzymes that release energy from carbs.
  • Nerve function: essential for normal nerve conduction and neurotransmitter production.
  • Heart muscle: needed for the energy supply of the heart — deficiency causes heart failure (wet beriberi).
  • Brain metabolism: the brain depends heavily on thiamin-driven glucose metabolism.

Different forms — and which to choose

Thiamin HCl / mononitrateStandard water-soluble supplement forms.
BenfotiamineA fat-soluble derivative that is better absorbed; studied for diabetic nerve problems.
Injectable thiamineHospital form for acute deficiency (Wernicke's).

Absorption in the body

How muchActively absorbed with a limited capacity per dose; little is stored, so regular intake matters.
HindersAlcohol impairs absorption and use — the main reason heavy drinkers become deficient.

Deficiency symptoms

SymptomsBeriberi — nerve damage (dry) or heart failure and swelling (wet); with alcohol, the brain disorder Wernicke–Korsakoff (confusion, eye signs, memory loss).
Who's at riskHeavy alcohol use, severe vomiting, bariatric surgery, and diets high in refined carbs.

Recommended intake

Adults ≈ 1.1–1.2 mg/day

Reference intakes (scale with energy intake):

  • Adults: ~1.1 mg ♀ / 1.2 mg ♂ per day

Best sources: whole grains, pork, legumes, seeds and nuts; refining removes much of it.12

Therapeutic use

EmergencyHigh-dose (often IV) thiamine for alcohol-related deficiency and Wernicke's — a hospital treatment.
NeuropathyBenfotiamine studied for diabetic nerve pain.

Therapeutic doses

Repletion under care; benfotiamine varies
EverydayDiet covers needs; supplements only for risk groups or deficiency.
AcuteMedical high-dose is supervised.

Toxicity & upper limit

No UL set
Upper limitNone established — surplus is harmlessly excreted in urine.1

Bottom line: thiamin comes from wholegrains, pork and legumes and is very safe. Supplements matter mainly for heavy drinkers and other risk groups — and suspected deficiency with confusion needs urgent medical thiamin, not a shop-bought tablet.

← All supplementsShort dietary version

References

Reference and upper-limit values are general adult figures from official bodies; individual needs vary. Therapeutic doses describe clinical/research use, not prescriptions.

  1. US NIH Office of Dietary Supplements. Thiamin — Health Professional Fact Sheet (function, forms, intakes, food sources, deficiency, therapeutic uses, upper limit, interactions). ods.od.nih.gov
  2. EFSA. Dietary Reference Values & Tolerable Upper Intake Levels for vitamins (European reference intakes and ULs). efsa.europa.eu

This article summarizes nutrition science from official health authorities and peer-reviewed sources for education. It is not a substitute for individual medical advice, and the doses given are not prescriptions — always consult a professional before therapeutic supplement use, in pregnancy, or alongside medication.

✓
Bodil Isaksson, Licensed Biomedical Scientist (Sweden)

At Food Health Lab we explain what the science says in plain language, and we cite our sources so you can check for yourself.

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