900 mg of Lithium is a very common dosage, as is 800 mg of Seroquel. With lithium it is actually the amount in your blood that is most important. Most psychiatrists consider that 1200mg a day is around the upper limit for Seroquel. The published doses were too low when it went on the market. As others have said, if you are not having bad side effects and the medication is helping, you likely are not being overmedicated. If you were overmedicated on these medicines I would expect you to feel very drowsy (interfering with your life/work/school) from Seroquel, or nauseated, anxious, tremulous with lithium. Is you hesitation due to the actual miligrams of medicine, or having to take the medicine in the first place?