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Vitamin B1 Side Effects

Generic name: thiamine

Medically reviewed by Last updated on Apr 17, 2022.

Note: This document contains side effect information about thiamine. Some of the dosage forms listed on this page may not apply to the brand name Vitamin B1.

For the Consumer

Applies to thiamine: solution, tablet

Side effects requiring immediate medical attention

Along with its needed effects, thiamine (the active ingredient contained in Vitamin B1) may cause some unwanted effects. Although not all of these side effects may occur, if they do occur they may need medical attention.

Check with your doctor immediately if any of the following side effects occur while taking thiamine:


- Soon after receiving injection only
  • Coughing
  • difficulty in swallowing
  • hives
  • itching of skin
  • swelling of face, lips, or eyelids
  • wheezing or difficulty in breathing

For Healthcare Professionals

Applies to thiamine: compounding powder, injectable solution, oral tablet


Local side effects have included tenderness and induration at the injection site following intramuscular use.[Ref]


Hypersensitivity side effects have included a feeling of warmth, pruritus, urticaria, weakness, sweating, nausea, restlessness, tightness of the throat, angioneurotic edema, cyanosis, pulmonary edema, and hemorrhage into the gastrointestinal tract. Anaphylaxis has been reported, especially after repeated injection. Collapse and death have also been reported.[Ref]


1. "Product Information. Vitamin B1 (thiamine)." Dixon-Shane Inc (2001):

Further information

Always consult your healthcare provider to ensure the information displayed on this page applies to your personal circumstances.

Some side effects may not be reported. You may report them to the FDA.