These studies only show a link between vitamin B12 deficiencies and weight gain, Matthew Cowling, D.O., a physical medicine and rehabilitation specialist in Madison, Wisconsin who specializes in weight loss, previously told The Edge
This makes them a good choice for patients who lack intrinsic factor, the protein responsible for helping your body absorb Vitamin 12 from foods
UK Guidance on Interpreting HbA1c Alongside B12 Status WHO 2011 guidance and NICE NG28 state that HbA1c should not be used for diagnosis when red blood cell turnover is abnormal
[Crossref] Weisberg I, Pamela Tran P, Christensen B, Sibani S, Rima Rozen (1998) Second Genetic Polymorphism in Methylenetetrahydrofolate Reductase (MTHFR) Associated with Decreased Enzyme Activity
But if you have a medically diagnosed deficiency, you can get these injections for free through the NHS