Are B12 Injections Effective for Treating Fatigue?

The pinkish-red liquid known as cyanocobalamin, or B12, has achieved legendary status among our patients.  It seems there is nothing a B12 injection can't fix.  Fatigued?  Forget sleep, stop by your primary care provider's clinic for a quick B12 upper.  Although this medication is rumored to solve a wealth of common health problems, primarily fatigue, is it actually effective?

A Brief B12 History

In the 1950's the vitamin B12 was identified and isolated in an effort to find the cure for pernicious anemia, a disease caused by B12 deficiency.  Pernicious anemia most commonly occurs in older individuals and can cause numbness, paresthesias and cognitive impairment.  It is typically caused by an immune reaction destroying the stomach's ability to absorb B12.  Pernicious anemia can also be caused by diet.  Vegetarians and vegans that do not consume animal products may become deficient in B12.  Some medications including PPI's, H2 blockers and metformin can also block absorption of B12 resulting in vitamin deficiency. 

The lofty claims surrounding B12's energy increasing abilities likely lie in it's ability to do so among those suffering from anemia.  In individuals suffering from a true B12 deficiency, regular B12 supplementation is effective in reversing the vitamin deficiency and increasing energy levles.  But, is B12 effective in treating fatigue among individuals without pernicious anemia or a B12 deficiency?

Is B12 Effective in Treating Fatigue for Individuals Without Vitamin Deficiency?

Surprisingly, despite the popularity of this supplement, little research has been done to evaluate it's fatigue-fighting abilities in individuals who do not suffer from a true B12 deficiency.  A 1989 study of individuals suffering from chronic fatigue syndrome showed that B12 injections were no better at increasing energy levels than placebo.  A flawed 1973 study indicated that B12 conferred no benefit for sleep, fatigue or appetite but that B12 recipients were "happier" and "felt better".  Clearly, given the limited scope and age of these studies, more information is needed to evaluate B12's efficacy.

Should You Recommend B12 to Your Patients?

Although research regarding B12 supplementation in individuals without deficiency is lacking, preliminary data suggests B12 is not the miracle drug advertisers and popular opinion make it seem.  There are no strict guidelines on B12 screening.  You should consider checking B12 levels in patients over the age of 50, vegetarians, vegans and individuals taking PPI's or H2 blockers or metformin especially if they suffer from symptoms of B12 deficiency. 

As far as your patients requesting B12 injections?  Inform them that once again, it seems there is no substitute for a healthy diet and a good night's sleep in increasing energy levels. 


While taking chemistry and nutrition classes at Vanguard University in Costa Mesa, CA., I learned that B-12 deficiency is epidemic in persons over 50 in the US and that supplementation is recommended by the US Gov't Council on Nutrition. They no longer recommend folic acid supplementation as the food supply has been fortified and has corrected folic acid deficiency since 1996.

Also, B12 would not likely help the sledgehammer fatigue associated with chronic fatique syndrome. CFS may actually benefit from b12 even if the patient doesn't report increased energy. Some of those patients may have a methylation defect and would benefit from methyl or hydroxy, rather than the cheap cyanocobalamin (which liberates cyanide ions). It is important to know that Chronic Fatique Syndrome has turned out to be a Lyme Disease diagnosis in an increasing number of patients. Many Lyme patients have perfusion and coagulation defects and would also benefit from B12.

Carolyn O'Connell

Yes, and it doesn't help that "Dr. Oz" who seems to have forgotten "do no harm", has contributed to what a hematology NP tells me is a "national shortage" of parenteral B-12, by recommending on his TV show the self-injection of B-12 for general well-being and many other vague "feel better" boosts. Appalling! The shortage makes it very important that providers do not humor patients who have been misunformed about B-12 by giving it to them simply because it's cheap and not likely to cause side effects. Doing that would also muddy the waters for patients who might actually be in need of testing, are unaware they have risk factors, but have heard about the fad and not wish to be a part of it.

Peri M