Complimentary and Integrative medical doctors have found that B12 is valuable in treating a wide array of health conditions. This vitamin has been useful in treating bursitis, hepatitis, facial paralysis (Bell’s palsy), vitiligo, herpes zoster, sciatica, trigeminal neuralgia, depression, dementia, chronic fatigue, diabetic neuropathy, asthma and infertility.
Vitamin B12 preparations are available for oral, sublingual, intranasal, and injectable use. When vitamin B12 is given intranasally it produced higher peak plasma concentration than those achieved with oral administration, but lower concentrations than those obtained with IM injections. However, the long-term safety of intranasal B12 has not been demonstrated, and it is possible that it could damage the nasal mucosa.
For most of the conditions mentioned above B12 does not work by correcting a deficiency. Rather, treatment efficacy seems to depend on the attainment of supraphysiological serum concentrations, concentrations that can be achieved only by IM injection. I have many patients who respond to IM injection but do not respond to oral, sublingual or intranasal therapy.
Which form of administration works best for you can only be determined by trying each one.