Someone should have been checking his thyroid levsls every 6 months after he had radiation even with no symptoms. Getting the dosage level correct is tricky and takes many months. Depending on how off the scale he is will depend on how long it takes him to get back to normal, usually a couple of months. Once he goes on the meds, he should be checked every three months until they get it under control. Since the in range scale is fairly wide, it is best to get back to your pre radiation TSH level if possible. Check with his doctors to see if they did thyroid test for baseline prior to his radiation treatment.

Take care,
Eileen

P.S. The thyroid test is a simple blood test and can be done when you have any other blood work done without drawing additional blood.