Sometimes there are few or no answers.
Some drugs will lower B12 absorption.
Long term antibiotics
long term use of acid blocking drugs for the stomach
increased needs (bodybuilders)
It might be that you used up your liver stores, and they are rebuilding now. 850 is not really high for injectable responses.
Injectable will give a quick fix, and show up fast on tests.
Oral takes longer.
I'd switch to 5mg of methylcobalamin daily on an empty stomach. Get tested again in 3 to 4 months.
There are many metabolic differences that are genetically driven in people concerning use of nutrients.
You may have a methylation DNA error...so using activated forms of B12 would be better for you than synthetic ones, like cyanocobalamin.
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All truths are easy to understand once they are discovered; the point is to discover them.-- Galileo Galilei
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Weezie looking at petunias 8.25.2017
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