If you are still getting clinical symptoms of hypothyroidism and your thyroxine dose/synthroid (T4) is already at 200 mcg/day, you may feel far better with another prescription for T3.
I think it is easier to adjust the doses if you have them separately, it does depend on what your doctor prefers or what drugs are available in your country.
They only prescribe one drug for thyroxine (synthyroid)or T4 and one for triiodothyronine or T3 in the UK.