One short night can leave you foggy, but weeks of short nights can nudge cortisol up, slow antibody response after vaccines, and make simple colds hit harder than they used to
Other than that, it does the job
B12 vitamin shots may cause pain at the injection site, mild diarrhea, and swelling
The Role of Bioavailability in Your Decision It is worth repeating that "when" you take a supplement matters very little if your body cannot absorb the "what." Many traditional glutathione pills are simply not effective because the molecule is too fragile for the human gut
Summary: Vitamin B12 supplements can occasionally cause mild stomach side effects including nausea, diarrhoea, abdominal cramping, and indigestion, though these are generally uncommon and temporary