I've only heard of one person who has taken
Phentermine in the past
with great succes, and when they started it again they had scary symptoms
like high blood pressure and jitteriness.
For everyone else, it seems that if you take it once and you're fine,
you'll be fine when you start again.
It really depends on the person, and since I'm not a doctor with access
to your medical history, I cannot tell whether it would happen to you.
Phentermine is not dangerous unless you shouldn't have been prescribed
it for any of the reasons below... Here's the quoted section from my
Phentermine prescription guide at Shoppe.MD:
"Inform your doctor of your entire medical history. Make sure to talk about any problems you have, such as an overactive thyroid, diabetes, glaucoma, high blood pressure, or emotional conditions. Before you buy Phentermine, talk to your physician if you may be pregnant, or are currently breastfeeding. You shoud also avoid consumption of alcohol because it will probably increase a possible side effect, dizziness. Phentermine is not designed for use by children or young adolescents. Talk to your doctor for more information about this medication."
So if you have any of those conditions, you want to talk to a doctor
before continuing Phentermine. However, most likely you're fine.