Bc of my symptoms, my doctor and i believe that i have hyperthyroidism. waiting on blood results. i'm 19 and pretty fit. would it be life threatening?

No: No, hyperthyroidism is not considered life threatening, although you shouldn't ignore it either. Untreated, it can cause undesired weight loss, racing/irregular heart beat (which then increases risk for stroke) & osteoporosis (which then increases risk for fracture or broken bone), etc. Check http://www.mayoclinic.org/diseases-conditions/hyperthyroidism/basics/definition/con-20020986 for more info