Dear Sir, We understand your concern. See, first of all i would like to know, that for what purpose you got your vaogotomy done at age of 14 years. You said you feel tired and have dumping syndrome for years. I hope you know what is dumping syndrome, or you are just referring it as a term for your tiredness. For your tiredness , i must tell that its because of anemia you have as a result of Vitamin B 12 deficiency. But i really want you to get your kidney functions tested, as you are taking metformin, so i assume you have diabetes, which can result in kidney dysfunction leading to anemia and tiredness. But, diabetic kidney disease usually doesnt cause Vit B12 deficiency anemia. One potential side effect of vagotomy is a vitamin B12 deficiency. As vagotomy decreases gastric secretion, intrinsic factor production can be impaired. Intrinsic factor is needed to absorb vitamin B12 efficiently from food. So i believe, with my answer, you have got your reason for having vitamin B12 deficiency. Stay Healthy Dr Anshul