When I first had B12 checked I was at 120 then had weekly shot for 10 weeks. 2 weeks later bad blood test again and only at 300. The doctor says now monthly shots for the rest of my life. I am still very tired and my legs are still really fatigued. She says no anemia so I am confused as to why my body stopped absorbing B12?? She says this is just common and has no direction going forward except for monthly shots. I am not vegan and I do not have celiac. I do however have IBS. Do you think 300 is low. My doctor says it should be at a minimum of 450. I am so very confused and wondering if something else is going on with my body. I am scheduled for ultrasound and cytoscopy as they found microscopic blood in my urine.