My hb level is 8.6 is it dangerous .iam 24 years old girl?

Yes it is: Anemia with a Hb of 8 grams in anyone is a serious problem. You need to go see a doctor who can find the cause and then offer you treatment immediately. The commonest cause of Anemia in young people is excessive blood loss(?heavy menses?). But it can be something more serious. Only further testing will reveal the exact cause. Give us some follow up after you have seen your doctor.