Vegetarians:  The primary sources of B12 are animal tissues. Even though B12 can be stored in the body (which is not true of other water-soluble vitamins), many strict vegetarians, over time, will become B12 deficient.

Inefficient Digestion:  Sufficient beneficial bacteria in the colon is required for the synthesis of B12. Recent research indicates that a majority of people do not have adequate levels of good bacteria in their digestive systems due to eating processed foods, consuming alcohol and tobacco, taking prescription medications, a lack of quality sleep and stressful lifestyles.

Inadequate B12: Many B12 supplements use the cyanocobalamin form which is not readily absorbed and must be converted by the body to the methylcobalamin form. B12 supplements are available as the methylcobalamin form which is a more effective way to acquire the vitamin.

Multivitamins do not provide enough B12 and often do not include enough of all the other B vitamins. The best option is to include a B Complex supplement or a multivitamin and assume this provides enough B12. Confusion occurs because all the B vitamins, except Folate and B12, are measured in milligrams (mg). B12 and Folate are are measured in MICROgrams (mcg). When the label indicates 50 or 100 mcg (those numbers are typical amounts for the other B vitamins), it’s easy to assume this is an adequate amount. But current research suggests B12 doses in the range of 5,000 micrograms daily. As a result, consuming only 50 or 100 micrograms results in a B12 deficiency.

Prescription Medications: Some prescription medications may block B12 absorption. Some of the most problematic prescriptions are the antigout and anticoagulant (blood clot prevention) medications. The latter includes coumarins, indandiones, Xa inhibitors, heparins and thrombin inhibitors (check with your doctor or pharmacist to find out if any of your medications fall in these categories).