Thanks for the query to H.C.M. Forum.
The side effects of Vitamin B 12 injections are as , Anorexia
, nausea, vomiting
, headache, hot sensation , fatigue, diarrhea
Vitamin B 12 never interfere in menstrual stages.
Late period may be due to another reason. Pregnancy
test is negative , so consult a Gynaecologist and get his opinion.