When my PCP first tested my B12 level, I was taking 1000mcg of B12, and the level cam back 1237. Last June, my neuro tested my B12 level, I was and still do take 5000mcg daily, and the level came back at 1016. I have no idea where my level was when I first started taking B12. I do know, my neuropathy is finally showing some improvement after nearly 5 years, and my neuro said to keep taking it. That's good enough for me!