This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: None, Subject name: Psychiatry
Prophylactic maintenance serum level of lithium is : 
Select and explain. 
A. 0.5 - 0.8 mEq/L, B. 0.7 - 1.2 meq/L, C. 1.2 - 2.0 meq/L, D. 2.0 - 2.5 meq/L
A: 0.5 - 0.8 mEq/L
Answer: A: 0.5 - 0.8 mEq/L 
Explanation: Blood lithium levels :

Therapeutic level : 0.8 - 1.2 mEq/L.

(For t/t of acute mania)

Prophylactic level : 0.5 - 0.8 mEq/L.

           (For relapse prevention in bipolar disorder)

Toxic lithium levels : > 2.0 mEq/L.