NICE guidance on metformin use recommends measuring B12 levels in patients with symptoms suggestive of deficiency
Anatomy & Pathophysiology The Pancreas and Insulin Regulation: The islets of Langerhans in the pancreatic parenchyma contain beta cells (insulin-secreting), alpha cells (glucagon-secreting), and delta cells (somatostatin-secreting)
[131] [132] Species from the following genera and the following individual species are known to synthesize B 12 : Propionibacterium shermanii , Pseudomonas denitrificans , Streptomyces griseus , Acetobacterium , Aerobacter , Agrobacterium , Alcaligenes , Azotobacter , Bacillus , Clostridium , Corynebacterium , Flavobacterium , Lactobacillus , Micromonospora , Mycobacterium , Nocardia , Proteus , Rhizobium , Salmonella , Serratia , Streptococcus and Xanthomonas
Low red blood cells will result in low energy
it is brought on by a lack of vitamin B12 in the diet or poor absorption