Thiamine taken by mouth is safe for most adults when used in the recommended daily amount. Rarely, people may have an allergic reaction to taking thiamine supplements by mouth (i.e., skin swelling, redness, itchiness). If you have an allergic reaction, stop taking the supplement and contact a health care provider.
Taking thiamine injections can cause feelings of warmth, tingling, itching, pain, rash, nausea, weakness, tightening of the throat, and sweating. In some cases, thiamine injections have caused death.
Thiamine appears to be safe for use during pregnancy and while breast-feeding when it is used in the recommended daily amount.
Coffee and tea appear to prevent thiamine from being used properly in the body. For people who get enough thiamine in their diet, this is not usually a problem. People who drink large amounts of coffee or tea and do not get enough thiamine in their diet may be at risk for thiamine deficiency.
Before taking any new medications, including natural health products, speak to your physician, pharmacist, or other health care provider. Tell your health care provider about any natural health products you may be taking.