Are You Getting Enough Vitamin B12? What You Need to Know

There’s a good reason to make sure you have enough vitamin B12 in your body. It’s a key vitamin that helps keep blood and nerve cells healthy, converts food into energy, and contributes to the creation of DNA, the genetic material in all your cells.

But most people in the United States don’t need to take a B12 vitamin supplement every day—or at all. While certain people (such as those over 50) may be at risk for a B12 deficiency, if you eat a balanced diet that includes animal foods, such as beef, chicken, fish, eggs, and milk, or fortified breads or cereals, you’re probably getting enough.

And yet, many people take vitamin B12 supplements. As many as 24% of men and 29% of women reported taking a supplement (either a multivitamin that contains B12, a B-complex vitamin, or a standalone B12 supplement), according to the National Health and Nutrition Examination Survey (NHANES). This occurred even though only 12.4% in the analysis had a B12 insufficiency (meaning they were at the borderline for a deficiency), and only 3% had a B12 deficiency.

Of course, there are certain situations where you should talk to your doctor about the possibility of needing more vitamin B12—if you are vegan (meaning you don’t eat animal products), are over 60, or have a condition or take a medication that could deplete your B12 levels, leading to a variety of symptoms (see below).

“Even though vitamin supplements are sold over the counter, any vitamin supplementation should always be discussed with a physician,” says Gary Soffer, MD, a Yale Medicine allergist and immunologist who offers guidance on the safe use of dietary supplements, among other things, within the Integrative Medicine Program at Smilow Cancer Hospital.

Below, Dr. Soffer shares more advice about vitamin B12.

Vitamin B12, also called cobalamin, plays a vital role in orchestrating key body functions. It's essential for DNA synthesis, red blood cell formation, nerve function, and, most importantly, converting food into energy.

It’s a water-soluble vitamin, meaning it dissolves in water. After the body uses these vitamins, leftover amounts leave the body through the urine. “So, if you get more than the recommended amount of vitamin B12 [see more on that below], chances are it won’t hurt,” Dr. Soffer says.

People may be at higher risk for a B12 deficiency if they:

• Are age 50 and older: Several factors contribute to B12 deficiency in people over 50. “First, aging can change a person’s gut [gastrointestinal (GI) system] over time, and the changes can make it more difficult for food to release B12 into the body or for the body to absorb it,” Dr. Soffer says. “Second, medications that many older people take, like metformin for diabetes or proton-pump inhibitors for acid reflux, can also impact absorption.”
• Are vegan or strictly vegetarian: Because most dietary intake of B12 comes from animal products, B12 supplements are recommended for people who eat a vegan diet or a vegetarian one with few eggs and dairy products. Although some non-meat foods, such as fortified cereals and nutritional yeast, may provide adequate intake.
• Are pregnant: Vitamin B12 levels tend to dip during pregnancy and return to normal after delivery. A prenatal vitamin should include B12, but since it is a key nutrient during pregnancy (contributing to fetal development, among other things), pregnant women who are vegan or have another reason to suspect a deficiency should talk to their doctor.
• Are recovering from surgery: A bariatric procedure, such as gastric bypass for weight loss, can reduce the amount of stomach acid necessary for B12 absorption.
• Have certain medical conditions: Problems that can restrict vitamin B12 absorption include pernicious anemia (a rare autoimmune disease that keeps the body from making a protein necessary to absorb B12), digestive illnesses, such as celiac and Crohn’s diseases, and immune disorders such as lupus, among others.
• Have alcohol use disorder: Too much alcohol can harm the digestive system and make it difficult to absorb vitamin B12.

Low levels of B12 can make you feel weak and cause anemia, loss of balance, and numbness or tingling in the arms and legs.

“B12 deficiency has been associated with mood disturbances, including depression,” Dr. Soffer says. “However, it's important to recognize that while a B12 deficiency may contribute to depression in some cases, it is not the sole cause. Depression is a complex condition influenced by many factors.”

Vitamin B12 deficiency is treatable, and treatment works best if the problem is diagnosed early. Depending on the severity of the deficiency, synthetic forms of vitamin B can bring levels back to normal. These are administered through shots in the muscle; nasal gels and sprays; or liquids, sprays, drops, or tablets taken by mouth. Some are available over the counter, while others are available only by prescription.

Doctors don’t check B12 levels routinely, but they may do so if a patient reports symptoms such as weakness, fatigue, tingling in the extremities (neuropathy), or cognitive changes. They also may monitor B12 in patients with medical conditions, such as anemia, and in those who have adopted a vegan diet.

A complete blood count (CBC), given as part of a routine physical examination, can provide some clues that vitamin B12 levels may be low. The levels can also be checked with a vitamin B12 level test. The results of the B12 test may be one of the following:

• Normal: B12 levels above 300 pg/mL
• Borderline: B12 levels between 200 and 300 pg/mL. Additional testing may help provide a diagnosis.
• Deficient: B12 levels below 200 pg/mL. However, a low B12 level won’t determine the cause of the deficiency, so further testing may be needed.

Some studies have shown that low levels of B12 may be associated with an increased risk of cognitive decline and dementia, but the evidence is not conclusive.

“It’s also essential to note that while a B12 deficiency may contribute to cognitive decline, it is not the sole cause of dementia,” Dr. Soffer says. “Dementia is a complex condition with multiple contributing factors, including genetics, lifestyle, and other medical conditions.”

While a B12 supplement may not cause harm, Dietary Guidelines for Americans, a government publication that provides nutrition advice to the public, recommends getting most nutrients primarily from food and beverages.

The recommended daily amount (RDA) varies, depending on age and other factors, but while the recommended dose for an adult is 2.4 mcg (micrograms), B12 vitamin pills are also sold in doses of 5 to 25 mcg, and even 500 mcg to 1,000 mcg or more; while the latter is usually considered safe, the body will absorb only a small percentage of that amount.

“Doctors are generally hesitant to recommend supplements if there is no clear indication for them,” Dr. Soffer says. “Food should always be the primary source of nutrition, but if someone feels they are not getting adequate amounts of B12—or any other supplement—for any reason, they should discuss it with their physician.”