Allergies and Health Conditions People with allergies or certain health problems should let their doctor know before getting a vitamin B12 shot
B12 blood levels just dont represent true B12 status reliably enough, and too many people are deficient even when their results fall within the normal B12 levels chart
(2004) Disruption of growth hormone receptor gene causes diminished pancreatic islet size and increased insulin sensitivity in mice

Patients who have undergone gastric banding should be aware of the following signs that may indicate falling B12 levels and warrant prompt blood testing: Neurological symptoms: Tingling, numbness, or 'pins and needles' in the hands or feet Difficulty with balance or coordination Memory problems, difficulty concentrating, or 'brain fog' Mood changes, including low mood or irritability Haematological symptoms: Persistent fatigue or weakness disproportionate to activity levels Breathlessness on mild exertion Pallor or a slightly yellowish tinge to the skin Other indicators: A sore, smooth, or inflamed tongue (glossitis) Mouth ulcers occurring frequently It is important to recognise that some of these symptoms particularly fatigue and low mood are non-specific and may overlap with other post-operative nutritional deficiencies, such as iron or vitamin D deficiency
Anyway let me know Yeah it's insane how long it stays in your body
For individuals with a deficiency, higher doses may be prescribed, often in the range of 1,000 to 2,000 mcg per day