Birth control does not generally cause weight gain. Although some women may notice weight gain while using it, birth control is unlikely to be the cause of significant changes in body weight.
Even though birth control can sometimes contribute to temporary fluid retention, changes on the scale are more likely to be related to increased muscle mass or the natural weight gain that can happen with age.
However, injectable birth control with medroxyprogesterone acetate (Depo Provera) does seem to cause some weight gain, especially in women younger than 18 and those with a body mass index, or BMI, over 30.
To find the birth control option that is best for you, it is important to see a gynecologist or other women's health provider. If you notice unusual or excessive weight gain, you should schedule another visit with your healthcare provider to check whether an underlying condition may be contributing to weight gain.