Vitamins contained in Vitamin B Complex are completely non-toxic even in high doses and usually no side effect occur. Sensitivity to Vitamin B
1, however may sometimes be encountered if administration is at prolonged intervals, irregular, or if initial dose is low and suddenly increased. Liver dysfunctions could also predispose patients to hypersensitivity reactions. Nevertheless, it must be stressed that hypersensitivity to Vitamin B
1 is very rare when orally given, unlike if administered by intravenous injection where hypersensitivity is more often encountered.
Vitamin E is usually well-tolerated. Large doses may cause diarrhea, abdominal pain and other gastrointestinal disturbances and have also been reported to cause fatigue and weakness.
Folic Acid is generally well-tolerated. Gastrointestinal disturbances and hypersensitivity reactions have been reported rarely.