A B12 pharmacokinetics puzzle
 

I just got the results of my B12 level. It was 351 pg/ml.

Now, this sample was drawn 6 weeks after I had begun supplementing oral methylcobalamin at 2mg/day. I skipped the oral doses for 2 days before the test.

Any educated guesses as to what my B12 level likely was before I began supplementing with the oral B12?

For extra credit, show your work. :)