I've been taking it a little over a month. Initially I had break through seizures that were shorter and less post-ictal conditions, but my gp can't locate a recommended blood level. My neurologist who prescribed the medication is in another town and I'm not scheduled to see him again for 2 months, so my gp is helping. I am 66, in good health, and female. My dose is 800 mg/day. Thank you so much for your assistance.