Hi...I'm bi-polar1...diagnosed 5 years ago.

I still don't know everything about lithium but am learning.
Duralth is still lithium carbonate, just releases differently, (from my understanding) Yes...you should be getting your blood levels checked on duralth (lithium carbonate)...every two months is usual until your levels are stablized. They say 1.4 tops but I maintained stability on .4 to .6 for three years. It all depends on how you are feeling on the medication. Everyone is different.
Now after my levels have been stable for five years, I only get blood work done every 6 months. My levels fluctuate between .5 and .9 now.
Your GP is the one who should give the order for the tests with a copy going to your pdoc. Get your test done exactly 12 hours after your last dose...any longer and you will not get an accurate reading. You should be having a regular thyroid test done as well. I found that cutting back on my coffee intake before a test actually increased my levels...my pdoc poofed poofed that idea...but I have read that...and it did work. So.

Hope I was some help...Take Care...Mo