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Everything You Need To Know About B12 Deficiency + How To Get Enough

Lindsay Boyers
Updated on August 31, 2021
Lindsay Boyers
Certified holistic nutrition consultant
By Lindsay Boyers
Certified holistic nutrition consultant
Lindsay Boyers is a nutrition consultant specializing in elimination diets, gut health, and food sensitivities. Lindsay earned a degree in food & nutrition from Framingham State University, and she holds a Certificate in Holistic Nutrition Consulting from the American College of Healthcare Sciences.
Image by Nadine Greeff / Stocksy
August 31, 2021

Vitamin B12 deficiency is often described as “sneaky” since it can be so difficult to pinpoint and diagnose. While clinical deficiencies are considered rare, subclinical deficiencies—meaning they’re not captured on traditional lab tests—can affect up to 26% of the population—an even sneakier problem. Because an untreated vitamin B12 deficiency can result in lasting effects, it’s important to recognize the signs and the risk factors as early as possible.

Why is B12 important?

Vitamin B12 is a water-soluble vitamin that plays several important roles in your body. One of the most notable is that B12 helps make red blood cells. Without it, the volume of red blood cells in your body greatly diminishes, and the ones that are made are oversized or irregularly-shaped and unhealthy.

B12 is also essential for keeping your brain and nerves healthy and for making new DNA. The vitamin also helps lower levels of homocysteine1, an amino acid that’s been linked to heart disease, stroke, dementia and osteoporosis. 

Signs of B12 deficiency. 

Because the signs of B12 deficiency are so widespread, it’s often difficult to recognize. You may have a handful of mild symptoms, or a more extensive list of severe symptoms. Some of the most common signs of B12 deficiency are:

  • Weakness
  • Fatigue
  • Decreased appetite
  • Weight loss
  • Constipation and other digestive problems, like gas or bloating
  • Numbness and/or tingling in the hands, legs, and/or feet
  • Balance problems
  • Difficulty walking
  • Swollen and/or inflamed tongue
  • Sore mouth
  • Memory problems
  • Confusion

And researchers from a study that was published in Applied Physiology, Nutrition, and Metabolism noted that If vitamin B12 deficiency isn’t corrected, it can lead to long-term complications, like:

  • Anemia
  • Neurological complications (unsteady gait and/or paralysis)
  • Depression
  • Dementia
  • Lethargy
  • Osteoporosis

There have even been some reports that severe vitamin B12 deficiencies can present as drug-resistant schizophrenia and/or psychosis.

What causes B12 deficiency?

When it comes to vitamins, one of the most obvious causes is a poor—or lacking—diet. Because vitamin B12 is found in the highest concentrations in animal-based foods, like beef, sardines, and dairy products, people following a vegan or strict vegetarian diet are at a higher risk of developing a deficiency2.

However, functional medicine doctor Amy Myers, M.D. explains that the journey of vitamin B12 from your mouth into your blood isn’t as simple as it seems, and because of this, the causes of B12 deficiency extend beyond your diet. “The absorption, assimilation and methylation of B12 is a very complex process, which leaves many opportunities for error,” she explains. “For this reason, even those who consume sufficient amounts of vitamin B12 in their diets could still have a functional B12 deficiency.”

Even if you’re consuming adequate amounts of B12, you can develop a B12 deficiency as a result of:

Pernicious anemia

Pernicious anemia is a condition in which the body doesn’t make adequate amounts of a protein called intrinsic factor. Intrinsic factor attaches to B12 and carries it to the intestines, where it’s absorbed into your blood. If you don’t make enough intrinsic factor, your body can’t absorb adequate amounts of vitamin B12, no matter how much you eat.

Digestive conditions

Digestive conditions that interfere with the way your body absorbs nutrients, like Crohn’s disease and Celiac disease, increase your risk of developing a B12 deficiency.

Advancing age

As you get older, your stomach gradually produces less stomach acid3, which is vital for the proper digestion and absorption of vitamin B12. If you don’t have enough stomach acid, your body can’t access what it needs.

Regular use of heartburn medication

Heartburn medications and proton pump inhibitors (PPIs) reduce the amount of stomach acid your body makes. And since you need adequate amounts of stomach acid to properly absorb vitamin B12, regularly taking this class of medications can increase your risk of a deficiency4.

Diabetes medication

The common diabetes medication, Metformin, can also increase your risk of developing vitamin B12 deficiency, although it’s not entirely clear how many people this affects. According to a report that was published in BMJ, the reported prevalence of B12 deficiency connected to Metformin ranges from around 6% to 52%—a huge range.

Bariatric surgeries

Bariatric, or gastric bypass and weight loss surgeries, often manipulate the stomach and small intestine, which can interfere with your body’s ability to absorb vitamin B125. In some cases, this can lead to a deficiency.

Heather Moday, M.D., a functional medicine immunologist and allergist, adds that B12 deficiency often comes down to—you guessed it—your gut. "B vitamin deficiencies tend to go hand in hand with gut problems," she previously told mbg.

How to test for B12 deficiency

If your doctor suspects a B12 deficiency, he or she will likely order a series of tests to get a full picture of what’s going on. One of the most telling tests is a complete blood cell count. This test can show if you have a low blood cell count and/or if your blood cells are large or abnormal—a sign of B12 deficiency anemia.

Another option is a homocysteine test. Just like it sounds, a homocysteine test measures the volume of homocysteine in your blood. Since B12 helps lower homocysteine, elevated levels can point to a deficiency.

If these tests are inconclusive or your doctor wants to dig a little deeper, he or she may also order a methylmalonic acid level test. Methylmalonic acid reacts with B12 to form a compound called coenzyme A (CoA). If your levels are high, it can indicate a deficiency. Myers adds that this test also measures the B12 stored in your tissues, which makes it more specific to vitamin B12 deficiency than other, more general blood tests.

Your doctor can also order a B12 test that directly measures the amount of vitamin B12 in your blood. However, while it sounds like this would be the quickest way to diagnose a deficiency, a vitamin B12 test isn’t the most accurate6, and it can be negatively affected by other lifestyle factors.

For example, if you take folic acid supplements or get a lot of folic acid through fortified foods, it can mask a B12 deficiency. Intrinsic factor antibodies can also produce false results, making it seem like you have enough B12 in your blood when you don’t.

Natural vitamin B12 deficiency treatment.

Our bodies don’t make vitamin B12. And since it’s a water-soluble vitamin, your body doesn’t store any extra either. It uses what it needs and then expels the rest when you pee. That means you have to make sure you’re consuming enough vitamin B12 every day to meet your needs—around 2.4 micrograms per day (unless you’re pregnant or breastfeeding, then that number jumps to 2.6 and 2.8 micrograms, respectively). If your diet falls short, or you have a condition that prevents the proper absorption of vitamin B12, you may need some help getting what you need.

Vitamin B12 in foods

As with any nutrient, it’s important to get what you can from foods. The richest food sources7 of vitamin B12 are:

  • Beef liver
  • Clams
  • Tuna
  • Salmon
  • Beef
  • Milk 
  • Yogurt
  • Cheese
  • Eggs

And while there aren’t many natural vegan and vegetarian sources of B12, there are some foods, like nutritional yeast and breakfast cereals that are fortified with the vitamin.

Vitamin B12 supplements

If you can’t get enough vitamin B12 from food or you need higher doses, you can also turn to supplements. The natural forms of B12, which include methylcobalamin, hydroxycobalamin, and adenosylcobalamin, are more easily absorbed and utilized by the body8 than synthetic forms, like cyanocobalamin, according to a 2017 report in Integrative Medicine

As for the difference in absorbability between them? The report notes that it’s negligible and any of them are a good choice. The exception is if you have digestive problems or a lack of intrinsic factor. 

If you have gut issues, Myers recommends a sublingual—or liquid—B12 supplement. If you have pernicious anemia or a severe deficiency, you’ll need regular B12 injections. Head’s up: These can only be administered by your doctor or a licensed healthcare provider, so if you fall into this camp, make sure you’re working closely with someone who knows your medical history and can help you navigate the proper treatment.

Bottom line

Your body relies on vitamin B12 for healthy blood cells and a properly functioning nervous system, but even if you’re eating plenty of B12-rich foods, you still may not be absorbing the vitamin properly. If you suspect a deficiency, work with your doctor to get the proper tests so you can start on a natural treatment plan that gets your levels corrected in a way that works for you.

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Lindsay Boyers author page.
Lindsay Boyers
Certified holistic nutrition consultant

Lindsay Boyers is a holistic nutritionist specializing in gut health, mood disorders, and functional nutrition. Lindsay earned a degree in food & nutrition from Framingham State University, and she holds a Certificate in Holistic Nutrition Consulting from the American College of Healthcare Sciences.

She has written twelve books and has had more than 2,000 articles published across various websites. Lindsay currently works full time as a freelance health writer. She truly believes that you can transform your life through food, proper mindset and shared experiences. That's why it's her goal to educate others, while also being open and vulnerable to create real connections with her clients and readers.