To date, no well-established toxic effects from the consumption of excess thiamin in food or through long-term oral supplementation (up to 200 mg/day) are known (15, 20).
A small number of life threatening allergic reactions have been observed with large intravenous doses of thiamin (15).
Presently, a tolerable upper level (UL) of intake for vitamin B1 (thiamin) has not been defined as there is no human data for adverse effects from high doses.
Because of the potential for interactions, dietary supplements should not be taken with medication without first talking to an experienced healthcare provider.
Authored by Dr Peter Engel in 2010, reviewed and revised by Angelika Friedel on 29.06.17