There is a theoretical case for using both in certain patients, targeting different physiological mechanisms simultaneously, though this approach is under evaluation and not yet standard of care
On the other hand, a vitamin B12 deficiency appears to cause a loss of appetite in some people, leading to weight loss rather than weight gain ( That said, the current evidence is too weak to suggest that a vitamin B12 deficiency has any strong or specific impact on weight be it weight gain or loss
The recommended dose of cobalamin is 250 g/cat by subcutaneous injection in cats up to 5 kg bodyweight
They can run simple blood tests to check your levels
Vitamin B12 deficiency is a real, treatable condition but the right treatment depends entirely on accurate diagnosis
Diets with low levels of protein and iron can also result in low vitamin B12 levels