I have always simply mixed the ground Metformin into my horse's feed with no problems.  The first time he had insulin over 200 and it came right down.  I just restarted Metformin again after an uptick in his insulin from 40 to 60, so hope the Metformin brings it down again...
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Ferne Fedeli  Magic & Jack   2007

Point Arena, Mendocino County, California
Case History