I'm taking phendermine and metformin for weight loss and i have horrible nausea all the time which one should i stop taking?

Diet Pills: Both. Phentermine is very dangerous to your heart and will not in any way lead you to any real or lasting weight loss. If you do not have diabetes, then please stop taking Metformin. It may only help with a pound or two of weight loss and not provide any long term benefit. I would also advise you to consider finding a medical provider that will be honest, compassionate and ethical with you.

It depends: The metformin is likely causing the nausea, but it's far and away the more important medicine to take provided you've been prescribed it for diabetes, prediabetes or PCOS. It's otherwise not a "weight loss" medicine. Metformin is typically dosed twice a day, so you could try taking it once daily while your body adjusts to it.