Headache: Headaches are a possible side effect of B12 injections, although they are typically mild and transient
Great experience from the initial call to finishing the product
If deficiency or low-normal levels are contributing, correcting them can improve energy and clarity
"Association of nicotinamide-N-methyltransferase mRNA expression in human adipose tissue and the plasma concentration of its product, 1-methylnicotinamide, with insulin resistance." Diabetologia
Peripherally, pancytopenia is most often observed, but only 1-2 of the major cell types (erythrocytes, leukocytes, platelets) may be depressed in some cases
While the back pain usually starts to ease up in six to eight weeks, how manageable that is for the patient depends on the specifics of the case and the patient himself