VetriScience Canine Plus Multivitamin for Senior Dogs : This is a vet-recommended blend of antioxidants, vitamins (folate, thiamine, riboflavin, niacin, ascorbic acid, vitamin E, A, D3, etc.), minerals (copper, calcium, selenium, zinc, iodine, iron, etc.), omega fatty acids from fish oil, and amino acids
Efficacy of sublingual and oral vitamin B12 versus intramuscular injection
You will not feel the full effects, weight loss may slow, and appetite suppression may be insufficient
Not getting enough vitamin B12 can cause tiredness and weakness, which can make it harder to stay active or stick to healthy habits
The rest of the work, sterile environment, identity verification, stability storage, dose administration, is harder and not amenable to a how-to article
longer-term toxicity studies have not been published