Cobalamin is my favourite Vitamin! Is that weird?? Oh well!
We already mentioned that a Vitamin B12 deficiency can cause a Folate deficiency.
Vitamin B12 I use in the clinic frequently. Weekly? At least monthly.
I don't often test for cobalamin deficiency, however, I do suspect that a lot of patients with inflammatory bowel disease are also deficient in Vitamin B12.
Vitamin B12 is important in protein absorption from the gut. It's a cofactor for enzymes, and most cofactors are important in many cell lines: gut, brain, bone marrow and more!
I started with supplemental injectable Vitamin B12 for pets with chronic vomiting and/or diarrhea, especially if they were thin body condition or losing weight. Now there is an oral cobalamin that is more bioavailable than other B12 supplements.
Here's an article for you on Cobalamin deficiency in cats.
And another one for dogs.
It appears that hypocobalaminemia is a poor prognostic indicator for long term survival. Since it is a water soluble vitamin, I just say to those clients, it's easy to supplement and not worry about overdosing them.