Vitamin B12
Vitamins + Supplements

B12: The Most Important Vitamin?

“Pins and needles” in the hands. Trouble walking. Severe joint pain. For one 62-year-old man, those symptoms turned out to be due not to a deadly illness, but to a deficiency in one of the most important vitamins: B12.

The case, published in the New England Journal of Medicine and cited in a Harvard Health Blog entry, could have been even worse: the Harvard Health post says that a severe B12 deficiency can lead to everything from incontinence and memory loss to deep depression and paranoia. (But, Harvard Health cautions, disregard extravagant Internet-based claims that B12 will solve issues such as Alzheimer’s, heart disease, fertility and eczema.)

Why is B12 so important? Because the body needs it to make red blood cells, nerves and DNA, according to Harvard Health. Although the recommended dose is 2.4 micrograms (mcg) daily, but that level may be difficult to reach. B12 cannot be manufactured by the body, so we need to get it from food or supplements.

Unfortunately, there may be issues with both food and supplements, Harvard Health says: some of us don’t consumer enough B12, while others can’t absorb it no matter what amount of the vitamin they are taking.

People over 50 may be especially affected: A survey cited by Harvard Health found that 3.2 percent of adults over age 50 have a seriously low B12 level, while up to 20 percent may have a borderline deficiency.

Among the possible causes of B12 deficiency:

A vegetarian or vegan diet: Because plants don’t make B12, people who eat a plant-based diet need to include fortified grains in their diet, or take a supplement.

Weight loss surgery: Operations such as stomach stapling get in the way of the ability to extract B12 from food.

Crohn’s disease or celiac: These also interfere with absorption of B12 from food.

Symptoms can include;

Numbness or tingling in hands, legs or feet; difficulty walking; anemia; a swollen tongue; jaundice; cognitive difficulties or memory loss; paranoia; weakness; fatigue; hallucinations.


Your B12 levels can be evaluated via a blood test. Harvard Health says you should consider asking your doctor about this if you are over 50; take a proton-pump inhibitor (such as Nexium or Prevacid) or H2 blocker (such as Pepcid or Zantac); take the diabetes drug metformin; are a strict vegetarian; have undergone weight-loss surgery; or have any condition that interferes with food absorption.


According to Harvard Health,  a B12 deficiency can be remedied either by weekly shots of the vitamin or high-dosage pills taken daily. Milder cases can be managed with a standard multivitamin.

A serious vitamin B12 deficiency can be corrected two ways: weekly shots of vitamin B12 or daily high-dose B12 pills. A mild B12 deficiency can be corrected with a standard multivitamin.

To read more entries from the Harvard Health Blog, click here. For more information on Harvard Health Publications, click here.