Exactly HOW I use retinoids on my neck and chest , The neck and chest are notoriously less tolerant to active ingredients like retinoids but they can still benefit., so heres how I use it, VITAMIN B12 (Generic) Injectable Solution, 1000 mcg mL, 100 mL vial Easy Refills Chewy Rx Before&After] My experience with B12 induced acne. Story in comments. : r SkincareAddiction Hello, my cat got recommended 0.5 ml of B12 every week. He got 5 shots already. At the moment he's eating less and less. Is the amount ok in your experience? I How to Give a Cat an Injection at Home: Step by Step Guide