Understanding Your Health

Vitamin B12: Your Questions Answered

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By Henry Ford Health System Staff

Most of us know that vitamins are essential for keeping our bodies healthy, but understanding how each vitamin functions isn’t always so clear. Case in point: Vitamin B12.  

According to long-standing research, B12 is vital for healthy nerves, production of blood cells and even optimal brain function. In fact, studies suggest that even a mild deficiency in vitamin B12 may put older adults at risk for dementia. Here, registered dietitian nutritionist Kelly Nohl answers frequently asked questions about this all-important nutrient.

FAQ: Vitamin B12

Although B12 is essential for good health, studies suggest up to 15 percent of the population may be deficient in the vitamin.

“One reason vitamin B12 is often in short supply is because the body can’t make it. You have to get it from food,” Nohl says. People who avoid eating foods that are rich in vitamin B12 — meat, dairy, poultry and fish — are more likely to have a deficiency.

Even if you’re eating the right foods, hormonal changes, digestive problems and diminishing muscle mass can make it tough for your body to absorb the vitamin B12 it needs.

Q: Who is most likely to be deficient in vitamin B12?

A: Because vitamin B12 is absorbed in the stomach, anyone with compromised digestion is at increased risk of developing a deficiency. Digestive issues such as celiac disease or reduced stomach acid (from aging or from medications that treat acid reflux) can get in the way of proper B12 absorption. People who have undergone bariatric surgery [may be at greatest risk of B12 deficiency because the surgery removes part of the stomach.

Other high-risk groups include those with anemia, people who restrict animal products (vegetarians, vegans, etc.), anyone who takes the diabetes drug Metformin, and elderly people. That’s one reason experts urge everyone over age 50 to consider taking a vitamin B12 supplement  or a multivitamin containing B vitamins.

Q: What are the consequences of a chronic B12 deficiency?

A: If left untreated, a chronic deficiency of vitamin B12 can lead to neurological and psychiatric problems. It can also interfere with nerve signaling and result in muscle weakness.

Q: How can I tell if I’m deficient in B12?

A: The only way to really determine whether you’re getting enough vitamin B12 is to ask your doctor for a blood test. Signs of a B12 deficiency tend to be vague, so most people don’t realize they’re at risk. A few key symptoms that might clue you in: muscle weakness and fatigue, depression, irritability, weight loss and decreased appetite.

Q: Who should get tested?  

A: Anyone who has a bowel disorder, chronic illness or who avoids eating animal products should be tested. Similarly, people over age 50 should also get tested. If you’re suffering from weakness, fatigue, depression or you just feel depleted, it’s important to rule out a B12 deficiency while also investigating other potential causes for your symptoms.

Q: How is a vitamin B12 deficiency treated?

A: In most cases, an over-the-counter oral or sublingual (under the tongue) vitamin B12 supplement — or even a standard B-complex vitamin — is enough to prevent or treat a deficiency. Vitamin B12, like all B vitamins, is water soluble, so it’s unlikely to cause harm (your body will just excrete the excess through your urine). In more severe cases of deficiency, or if you have a digestive disorder that inhibits your body’s ability to absorb B12, your doctor may prescribe vitamin B12 injections.

Q. Should I take a vitamin B12 supplement?

A. It is not recommended to start taking any supplement without checking with your physician and/or registered dietitian nutritionist first. Taking excessive amounts of vitamin B12 can mask health conditions, such as pernicious anemia, delaying the treatment that you may need. If you are feeling muscle weakness, fatigue, depression, irritability, weight loss and/or decreased appetite, make an appointment with your doctor so he or she can diagnose the actual cause.  

Related Topic: 8 Myths About Vitamin Supplements

Staying in the Safe Range

A B12 deficiency can cause serious problems, but for most people it’s remarkably simple to treat. The nutrient is found in fish, meat, eggs and dairy products. It’s also in fortified grains, breakfast cereals and nutritional yeast products.

If you’re concerned about getting adequate vitamin B12[, ask your doctor to test your levels.

To make an appointment with your doctor or find a primary care provider at Henry Ford, visit henryford.com or call 1-800-HENRYFORD (436-7936).


Kelly Nohl is a registered dietitian nutritionist for the Henry Ford Center for Health Promotion and Disease Prevention