Phentermine 37.5 is a weight loss medication that has been approved by the Food and Drug Administration (FDA) since 1959. It is a prescription medication that works as an appetite suppressant, helping you to control your cravings and reduce your calorie intake. This medication is typically recommended for individuals who have a body mass index (BMI) of 30 or higher, or for those with a BMI of 27 or higher who also have weight-related health issues such as high blood pressure or diabetes.