text: If you get a prescription from your doctor, it's around $35. On the net it's more like $80. If you really need to lose weight a doctor will have no problem prescribing it for you. If you don't, why do you want it? The side effects are sucky--insomnia, hot flashes, dizziness, thirst, dry mouth. (I'm on it right now.)\nYou can go to the phentermine web site and look at their prices and then call some local pharmacies and see the difference.