self administering b12 injections B12 Shots at Home: NHS

The injection volumes are smaller for higher concentration solutions and larger for lower concentration solutions

Contraindications/Precautions Cyanocobalamin is contraindicated in those with hypersensitivity to cobalt moiety or cobalamin molecule due to the risk of anaphylaxis (9)

But this isnt to say you need more AHK-Cu the older you get

Conversely, a few studies reported high levels of vitamin B12 in the blood of patients with a worse COVID-19 outcome 48,49 potentially due to cytolysis leading to the release of intracellular B12 into the plasma and disrupted B12 clearance by the liver, which is often affected in these patients 50