Theyre legal to use only in experimental settings but are increasingly available online or from wellness clinics and other unregulated entities
People with symptoms of vitamin B12 deficiency It is a good idea for anyone with the following signs and symptoms of a vitamin B12 deficiency or pernicious anemia to consult a doctor: People with gastrointestinal issues Conditions that affect the gastrointestinal tract may affect vitamin B12 release or absorption, including: pernicious anemia, which can lead to gastric atrophy, or damage to the stomach fish tapeworm infestation bowel or pancreatic cancer folic acid deficiency overgrowth of bacteria in the small intestine diabetes thyroid disease Crohns disease celiac disease chronic pancreatitis People who have undergone gastrointestinal surgery, including weight loss, may have fewer cells necessary to secrete stomach acid and intrinsic factor
These can include redness at the injection site, mild nausea, or a feeling of warmth
The body can then use the fatty acids for energy
High-fat meals are the worst offenders for nausea because fat already slows gastric emptying on its own
PMID 40789979 2025 review emphasizing the gap between preclinical and human evidence