Hi everyone. About a year ago I tested just under 200 (blood test). Doc put me on 400mcg daily, so I've taken it for about a year. Recent blood level was 1239. It seems logical that the increase would be solely related to supplementation. However I got somewhat confused reading through that 2013 article which tied in high levels to sinister causes.
While it seems obvious, can I relate this increase to my year's worth of supplementing? I have no symptoms to suggest something going on.
Rob
If you are supplementing B12, there's no point in having a normal blood test for it, because the results would be skewed. You'd either have to stop the B12 for five months, or have an active test. As you don't give ranges, I can't tell which one it was. 
I think sinister causes are related to high B12 levels found when not supplementing, not high levels found when supplementing. Your body should just clear out excess, unless you have some other kind of severe condition which I'm sure your doctor would have told you about. You could ask your doctor what your cause of vitamin B12 deficiency is, whether you need to keep supplementing and whether you should adjust your dosage. Hopefully that will give you peace of mind.
What are optimal B12 and Folate levels?
I'm slightly concerned about high levels of B12.
Does anyone know anything about iron, ferritin, folate and b12 levels? 
Optimal ferritin levels: what unit of measurement?
Desirable levels of vit B12, folate, ferritin etc
