Medical gelatin is the main body of hollow capsules, which are composed of a cap and a body made of medical gelatin and excipients.

Alkaline gelatin with high freezing strength (high freezing power) (Type B-B gelatin is bone gelatin or cow skin gelatin that has been limed) and acid gelatin (Type A-A gelatin is pig skin gelatin or cow skin gelatin that has not been limed) can be used to manufacture hollow hard capsules. The two types of gelatin can be mixed or used alone.