This can be due to sensitivity to the ingredients or an allergic reaction
That means: It is not FDA approved for general human use outside clinical trials
Vitamin B12 is Reducing the chances of developing vitamin B12 deficiency, and complications that may occur in the future as a result of vitamin B12 deficiency, such as: heart disease, nervous system diseases, vision loss, and problems in the nervous system of fetuses born to mothers with vitamin B12 deficiency
doi:10.1016/j.fertnstert.2006.06.015
The most common side effects of Foundayo include nausea, constipation, diarrhea, vomiting, indigestion, stomach (abdominal) pain, headache, swollen belly, feeling tired, belching, heartburn, gas, and hair loss
B12 is 659pg/mL and folate is the same (this was 4 days after my most recent injection), also taking a B-complex vitamin daily with 15mcg of b12