According to USDA Agricultural Research Service data based on NHANES, approximately 6% of adults aged 60 and older in the United States are vitamin B12 deficient, defined as plasma B12 below 148 pmol/L (2009)
But, B12 mixes can have different strengths
This can minimize the risk of adverse reactions and maximize the efficacy of the treatment
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That said, it is still a good idea to keep an eye on your pet after each dose and check with your veterinarian if you notice anything unusual, even though adverse reactions are considered very rare
Some patients, particularly those with neurological involvement, may benefit from more frequent dosing (every 2 months rather than 3 months), but this should be medically supervised rather than self-adjusted