Synthroid low dose symptoms. high, the next visit it's too low . . . or over-treatment (when your dose of levothyroxine is too high). . . Cause my breathing has been getting really bad this past week, only taking the med for 2 weeks, now I'm having bone pains in both arms . . . Our Symptom . . lowered my dosage to . . . Do not stop or change your dose of Synthroid . . Symptoms of low thyroid hormone levels include . . . . . Some symptoms of a synthroid overdose can be life threatening. unless ... more