Can i take phentermine safely? 17, 5'1, 160 lb female. i was thinking of cutting 37.5 mg tablets in half and taking it. i have low-normal blood pressure and no health issues other than being severely overweight. is this an awful idea?

Only if so prescribed. At your age a strict diet with gradual exercise should suffice. You are only in the overweight range BMI 30 and the benefits of starting a habit forming medicine may not outweigh the risks of it. Talk to your pediatrician about your options.

Phentermine is an amphetamine and works by speeding up your metabolism. It's not good for your health. Go here to see a list of side effects: https://www.drugs.com/sfx/phentermine-side-effects.html. There are healthy ways to get to a normal weight. One of the best is using a ketogenic diet. Here is a good place to get information: https://www.virtahealth.com/faq/what-can-i-eat-on-a-ketogenic-diet