Which of the following represent the theraputic level of Lithium in serum?

Lithium is most commonly used in the treatment of bipolar depression. It has a low toxic : therapeutic ratio. The therapeutic level of Lithium in serum is 0.8 - 1.2 mEq/L. Lithium toxicity occur when serum lithium levels exceed 1.5 to 2 mEq/L. Hence frequent bood tests are done to monitor the drug levels. Lithium is fully metabilised by the kidney. Hence, dehydration could cause the drug levels to rise. Ref: Current Medical Diagnosis and Treatment 2013, chapter 38.