One of the common side effects vitamin B overdose is a skin rash. The skin may appear flushed and welts may appear all over the body. There might be a complaint of an itchy sensation throughout the body. The extent of skin rash depends on the intensity of vitamin B complex overdose.
Another common side effect of vitamin B overdose is gastrointestinal problems. When a higher dose of vitamin B is taken, people may suffer from indigestion, nausea or mild diarrhea. People with a prior history of gastrointestinal problems and aged individuals are more likely to suffer from intense stomach cramps and severe diarrhea after taking high doses of vitamin B.Six Possible Side Effects of Vitamin B Overdose | Medicover Hospitals