I was giving my husband Vitamin B 1 in the dose of 500 mg in error....The Dr had given instructions for 2000 mg of B 12 and 100 mg of B 1 So I ws giving him 400 mg more !!! When I realized it, I cut it down to 250 mg, and intended in a week to reduce it to the 100 suggested so as not to shock his system. This all started about a month ago.......now this week he has experienced vertigo three times since I reduced the dose from 500 to 250....he was taking the B 1 and B 12 at the Drs instructions for theuropthy which MiHGT have been also in his ear the Dr said, which MIGHT be causing the vertigo....The Dr is not there until Tuesday and I wondered if I should either stop the B 1 or go back to the B 1 500 mg to see If the vertigo goes away....It was a problem until he started the B 12 and B1 and then it went completely away for the 6 weeks he was taking the 500 B 1 and the 2000 B 12 Thnk you....