How soon could i go for blood work after first reduction of tapazole (methimazole) from 15 mg to 10 mg? tsh was 5 last time (.01 prev.) could tsh rise further?

Many variables.: Individual doctors have usually developed a system that works for them. I typically recheck thyroid labs 4-8 weeks after a dose change, but in some circumstances would check sooner; in other situations, i might wait a little longer.

4-6 weeks: Every 4-6 weeks until stable then less. This should only be something confirmed by the doctor adjusting your medicine of course. Checking thyroid intervals too soon and the results are unreliable--this is why tests are not done sooner unless you are having concerning symptoms--in which case, your doctor wants to know. And, yes, your TSH may still alter or rise but this is unpredictable.