Recommending OTC vitamin B12

OTCs today

Many clinical trials have proven that oral supplementation of vitamin B12 provides adequate replacement for deficiencies. Despite the consideration of poor absorption of the oral form due to lack of intrinsic factor or gastric acidity, oral supplementation may be preferred in most patients.1 Pharmacists should feel confident recommending oral supplementation of vitamin B12 to elderly patients for mild to moderate deficiencies and prevention or treatment of pernicious anemia.

Back to basics

Vitamin B12, or cyanocobalamin, is important to the formation of blood cells and nerve cells throughout the body. Vitamin B12 deficiency, found mostly in the older population, leads to symptoms of malaise, memory impairment, and even neuropathy. Typical causes of deficiency include malabsorption or inadequate intake. Supplementation typically involves weekly to monthly injections, often for life.2 Regular oral supplementation of OTC vitamin B12 could save patients money, time, and inconvenience.

A review by Andrès et al.1 reported that 1,000 µg vitamin B12 taken once daily provided clinically meaningful outcomes. Researchers in multiple studies observed increases in hemoglobin, a normalization of serum B12 and mean corpuscular volume levels, and resolution of some neurological symptoms after only 4 months of oral therapy. These effects are comparable with traditional injections of vitamin B12 for the same length of time.

In a prospective, randomized, controlled study by Kuzminski et al.,3 a dose of 2,000 µg taken once daily was compared directly with a traditional injection schedule. After 4 months, the group treated with OTC vitamin B12 had significantly higher B12 levels compared with those achieved with the injectable version. A dose-finding trial by Eussen et al.4 found that a minimum dose of 500 µg provided similar effects.

Making a recommendation

In accordance with these data, pharmacists can recommend a daily dose of 500 µg to 2,000 µg vitamin B12 to patients requiring treatment for mild to moderate pernicious anemia or a B12 deficiency. Oral and sublingual tablets are available in strengths ranging from 500 µg to 2,500 µg; either dosage form will provide a similar effect.5 Sustained-release formulations of vitamin B12 have not been well studied and therefore are not recommended by most physicians or pharmacists. Patients with more severe deficiencies should speak to their physician about possible injection therapy and should remain under careful monitoring until the deficiency is resolved.6

Counseling pearls

Most vitamins contain 6 µg to 25 µg vitamin B12 per tablet; amounts may be higher in vitamins targeted for older people. Advise patients that B12 absorption also can be hindered by regular alcohol use and certain medications. Reduced calcium intake may cause low B12 levels due to the action of intrinsic factor, which is dependent on calcium channels. Medications that relieve symptoms of acid reflux also may cause decreased dietary absorption as a result of decreases in calcium absorption and lower gastric acidity.5 Patients taking any of these medications may be candidates for a B12 supplement, so talk with these individuals to identify opportunities for recommendations.


  1. Andrès E, Fothergill H, Mecili M. Efficacy of oral cobalamin (vitamin B12) therapy. Expert Opin Pharmacother. 2010;11:249–56.
  2. Therapeutic Research Center. Treatment of vitamin B12 deficiency. Pharmacist’s Letter/Prescriber’s Letter. August 2011.
  3. Kuzminski AM, Del Giacco EI, Allen RH, et al. Effective treatment of cobalamin deficiency with oral cobalamin. Blood. 1998;92:1191-98.
  4. Eussen SJ, de Groot LC, Clarke R, et al. Oral cyanocobalamin supplementation in older people with vitamin B12 deficiency: a dose-finding trial. Arch Intern Med. 2005;165:1167–72.
  5. Sharabi A, Cohen E, Sulkes J, Garty M. Replacement therapy for vitamin B12 deficiency: comparison between the sublingual and oral route. Br J Clin Pharmacol. 2003;56:635–8.
  6. National Institutes of Health. Dietary supplement fact sheet: vitamin B12. Accessed at, October 5, 2012.