My uncle's vitamin b12 level has crossed 9000.he's going into depression also.he is also a diabetic.I want to know what can be the consequences of this elevated vit b12 level?and what should we do to control it as he's a vegetarian.

He should see his doctor and have a liver function test done. Elevated b12 is usually caused by disease, most commonly liver disease.

[normal vitamin b12 values 200 - 900 pg/mL] your uncle's b12 level has crossed 9000..
He should see his doctor..
hope your uncle gets well soon!