Your B12 is in the low range and worthy of treatment. Your doctor should have drawn a methylmalonic acid and homocysteine to prove that this is what was making you this ill.

But you do seem much more ACUTELY ill than most of us, who have had symptoms come on a bit more gradually, and it sounds as if you should be closely and aggressively followed.

If your doc has drawn the mma and homocysteine, start the methylB12 immediately. But you are probably one of the few people for whom a wait of a few days would be worthwhile if the other tests weren't drawn yet.

Just that as suspicious as you B12 is, your diffuse symptoms coming on quickly could be something else.

So I'd say blood test THEN lots and lots of B12. But quickly.