All the tablets give Just 15 micrograms / Tablet . As over & above that intake will not be absorbed due to intrinsic factor. And it will be wasteful. Even absorbed due to mass diffusion effect like large dose or Injection will be excreted as it is water soluble .
Look out how much vit B12 is in fortified food in days quantity of food.
Where as with Vit D it is a different issue . It is fat soluble , excess intake will be stored and will be toxic to the body .
Regarding Vit D check up with a dependable Lab for the concentraton . When below 40 % , you will be prescribe high dose Vit D tablets for a suitable time to reach 100 % . more