Your doctor will typically monitor your response through clinical improvement and blood tests such as full blood count, rather than rechecking B12 levels after starting injections
It is the standard diluent used across virtually all peptide research protocols for reconstituting lyophilized peptides
[Google Scholar] Tandon R., Thacker J., Pandya U., Patel M., Tandon K
Each lot is tested by an independent analytical lab

Best B12-rich foods for vegetarians: Cows milk: two cups daily provides approximately 2.4 mcg meeting the full adult daily requirement Greek yogurt: a 6-ounce serving provides 0.9 to 1.3 mcg a valuable daily staple Cottage cheese: one cup provides approximately 1.0 mcg Swiss cheese, mozzarella, and other hard cheeses: contribute 0.7 to 0.9 mcg per ounce Eggs: two eggs provide approximately 1.2 mcg a useful contribution but not sufficient alone Fortified breakfast cereals with milk: can provide 1.5 to 3+ mcg per meal Fortified plant milks (if choosing plant-based dairy alternatives) Fortified nutritional yeast: a valuable flavoring ingredient providing 2 to 8 mcg per tablespoon Practical daily B12 strategy for vegetarians: Have two cups of milk or two servings of dairy daily Include an egg or two at breakfast or lunch several times per week Use fortified cereals as a reliable daily B12 contributor Use nutritional yeast as a cooking ingredient for an additional B12 boost Monitor B12 levels through blood testing annually Vitamin B12 Options for Vegans This is one of the most important nutrition conversations for anyone following a vegan diet

Aim the needle at the inner wall of the vial, not directly onto the lyophilizate powder