My b12 level is high 980. what's the cause?

Supplement too high: High B12 level can be related to taking too much B12 supplements; most of time excess is excreted because being water soluble vitamin.In rare cases, excess B12 supplementation may cause numbness or tingling in the arm, hands and face. Excess vitamin B12 may contribute to anxiety symptoms, panic attacks, insomnia, worsen hyperthyroidism, rashes.