Radioactive Iodine Untake and Scan ?

I have recently been diagnosed with Hyperthyroidism. I was referred to an Endocrinologist who just asked me questions, checked my heart rate and neck,. He then wrote out 2 scripts for tests with no explanations. The first was a blood test and the second for a "thyroid Uptake Scan" In researching this test I feel hesitant to complete such. Everything inside me says there in not to do it. When I called the Endo's office to say such I was told the doctor would want to see me to explain why I would refuse such. Aren't there other tests to diagnose Graves Disease or whatever else could cause this? Am I being to nervous and cautious? What should I do?