Helped with brain fog

I believe covid messed up my ability to absorb b12 via supplements or food but lab results always showed high b12. Pat K, a nurse who suffered b12 deficiency, says this is because higher levels of b12 can be measured if any has been taken via a multivitamin or energy drink in the last 4 months. There are also papers showing many places where b12 absorption can go wrong - small intestine bacterial overgrowth, low stomach acid caused by any condition like vagal nerve damage, common conditions like h pylori, antacids, use of Metformin long term can also decease absorption.