Approximately 3 years ago I was diagnosed as being B12 deficient, however, the cause is not known as I tested positive for the Intrinsic Factor AB. My doctor has prescribed shots for me every 2 weeks and this is not enough! I know my body well enough to know. At first this regimen was working, but now my symptoms are coming back (fatigue, brain fog, weight loss, imbalance, awkward gait).