define the toxicity of vitamin b12intake of 1000

Question

Define the Toxicity of Vitamin B₁₂?

Intake of 1000 μg vitamin B₁₂ has never been reported to have any side-effects.  Similar large amounts have been used in some preparations of nutritional supplements without apparent ill effects. However, there are no established benefits for such amounts. Such high intakes thus represent no benefit in those without malabsorption and should probably be avoided.