Gum bleeding was gone with 7- b12 inj 500 mcg daily.after the loading dose,it started again.taking sublingual.but does not help? cause of gum bleding?

Bacteria: number 1 cause is the presence of gram negative anaerobic rod bacteria irriating the periodontia.

Gingival bleeding: Need to find out if your clotting factors are normal and platelet count among other blood tests. Please see your physician for blood studies for a bleeding disorder or a referral to a hematologist. Is there a reason for taking tranexamic acid or taking other supplements? Some supplements as well as motrin and aspirin will contribute to abnormal bleeding. Alternatively, gingivitis will also bleed.

Infection: Probably gum disease. Easily treatable by a competent Dentist or Periodontist in its earliest stages. Treatment becomes more complex as disease advances. Please make appointment with Dentist. Unless lab tests show that you have a B12 defficiency (seen often in strict vegetarians), bleeding gums most probably due to infection.