After being diagnosed with 'boarderline B12 deficiency' my GP prescribed hydroxocoalamin injections (1000mcg). The loading dose was disappointing to begin with and I returned for a further blood test. This revealed large amounts of B12 in my blood stream, but I still felt sleepy/confused/joint pain. Eventually, after about a month, it began to improve. I felt great for about 5 weeks, no mid day sleeping. As my fatigue started to return I was looking forward to the first of my 3 monthly maintenance injections...however that was 2 months ago and I have had no benefit from it at all this time. Will this improve, is there a larger dose, how do I know if my body is having trouble taking up the B12???