Yes, the B12 test will reflect some increase from 3 weeks use.
You won't know what it was before supplementation. Stopping for 5-7 days before the test will remove some excessive values from the supplement, but the result is likely to be higher than before any was used.
The MMA test will reflect if the B12 present is being utilized properly. When B12 cannot work (say it is cyano form only), then MMA builds up in the blood to a high value.
Sometimes people with low B12 show high folate levels. This is called the methyl trap...and that is why they are both tested.
This information is mostly used by hematologists to provide information for the treatment of the various types of anemia.
In a 70 yr old, there are complicating factors:
http://www.cdc.gov/ncbddd/b12/detection.html
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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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