Hi KK,
Recent studies recommend using a 10 mg dose of Tapazole to start out since higher doses are likely to lower the WBC count. Ask for the WBC value. Dangerously low would be lower than 1.0. I've heard doctors say dangerously low when the WBC count was just slightly low, like 4.0. Liver enzymes are also usually elevated when the ATD dose is too high.
If the ATD dose was low and still caused problems, than surgery is usually a better option than RAI. Radioiodine stimulates the immune system and worsens the autoimmune process. This often leads to thyroid eye disease, pretibial myxedema, and other autoimmune diseases.
Partial thyroidectomy is a good option because your can keep some of your thyroid tissue and produce a small amount of natura hormone. Thyroid replacement hormone isn't always well tolerated.
The size of the gland is also important in considering what type of replacement hormone works best.
See http://hashimotos-encephalopathy.blogspot.com/
I'm going to write a blog on this lady's experiences with treatment for Graves' disease, but it's very pertinent to your question.
Best, Eaine