After loosing 18 pounds and trying for 10 more will my thyroid medication need to be adjusted? feeling jittery and heart racing. 125 mcg's now .

Yes most definitely: you will need to look at the thyroid tests again and see if a dose adjustment is in order. Losing weight not only decreases the body's burden and blood flow requirement, it also increases the basal metabolic rate and effectively increases some hormone production in the body. If you feel that your thyroid medication may be too much at this point, it probably is. See a healthcare provider.