Vitamin B12 is available in both synthetic and natural forms. The natural form is by far superior. Unfortunately, most inexpensive nutritional supplements contain synthetic vitamin B12.

Cyanocobalamin is the synthetic form of B12 contained in many nutritional supplements. It consists of a cyano group attached to a cobalamin molecule. The cyano part of the compound is what makes it a synthetic.

For people who have difficulty detoxifying the cyano group, cyanocobalamin can cause serious adverse effects, even blindness.

There is no reason to use a synthetic form of vitamin B12 when natural, bioidentical forms are readily and inexpensively available.

Hydroxy- or methyl-cobalamin are both natural, bioidentical forms of vitamin B12 that are easily absorbed in the body without any serious side effects.

The worst adverse effect of natural B12 therapy is in patients that have an allergy to it. Fortunately, vitamin B12 allergies are not common.

Vitamin B12 is available in oral or injectable forms. Absorption of oral dosing is not as effective because it requires multiple, complex steps, as well as adequate stomach acid production.

My experience has shown that people younger than 25 years old can effectively absorb vitamin B12 as long as they produce enough stomach acid. For those over 25 years, the absorption of oral B12 continues to decline a great deal over time.

When using oral vitamin B12, I recommend sublingual forms, which are better absorbed than regular oral forms — especially when a person has inadequate stomach acid production.

On the other hand, injectable hydroxy- or methyl-cobalamin are inexpensive (about the same as oral doses), very safe, and much more effective.

When using injectable B12, I suggest 1 mg per injection. I have not seen added benefits or harm from a larger dose.

My usual prescription for injectable B12 is 1 mg once or twice per week. In times of stress, the frequency of injections can be increased temporarily.

If you suffer from a serious illness such as debilitating fatigue, PA, or neuropathy, more frequent injections of vitamin B12 can provide better results.

I often instruct patients to inject 1 mg daily for two to four weeks, then lower the frequency to once or twice per week.