When i take biotin for hair ,this tablet gain weight this is right or no?

Need more info: I doubt that biotin, a vitamin, causes weight gain. There is a possibility though, at least theoretical, that some component in the purchased product causes weight gain. That would depend on the specific manufacturer of your product. I think you should look at another explanation - more calorie intake, less activity, less sleep - as the cause for your weight gain. Hope that helps.

Hair loss: Biotin deficiency is rare, taking biotin supplements for hair loss is not scientifically proven to reverse hair loss. Some people develop gastrointestinal side effects and have to stop the supplement. See your doctor for a full evaluation of your hair loss to determine potential reversible causes. I am not aware of weight gain on biotin.