GCG and type 2 diabetes mellitus: Although the data was obtained before the introduction of newer drugs for T2DM (eg sodium-glucose transport protein 2 inhibitors and glucagon-like peptide 1 agonists), key aspects of primary-care clinical practice have not changed: metformin (the major determinant of B12 deficiency) remains the mainstay of T2DM treatment [12]; and to lower cholesterol, we are still advocating that patients limit dietary cholesterol to less than 200 mg per day by reducing consumption of eggs [82], shellfish, and organ meats [83–85] (otherwise rich dietary sources of B12) [86].