Does sertraline cause wieght gain at which dosage it cause wieght gain i'm taking 50 mg sertraline ?

Can cause: It sometimes causes weight gain, but in a majority of cases it doesn't. When it does the amount varies: 50 mg or higher. But since you're taking it I would focus on the likelihood that it won't cause it for you, and if it turns out that it does, you can address this with your prescriber. Worse case: you simply stop the medicine, (with guidance about decreasing in steps).