Can I take a vitamin that is put in a capsule made of gelatin?

It is permissible to consume gelatin derived from animals lawful for human consumption. However it is prohibited to consume gelatin derived from animals prohibited for human consumption (in Islamic law).
Generally speaking, it is permissible to consume gelatin based medications if it is prescribed by a specialized physician and it is not harmful. This is because the gelatin used in manufacturing capsules is transformed into different enzyme after going under acids and water processing during manufacturing.