Why Your Doctor Won’t Treat You for This Vitamin Deficiency

Dr. Frank Shallenberger, MD

January 6, 2020



Do you feel weak and tired compared to the way you used to feel? Is your memory starting to slip? Is your balance off? Are you dizzy or depressed?

A lot of folks over 60 suffer from one or more of these symptoms. Some doctors will tell you, “You’re just getting old.” While that may be true, it doesn’t mean you have to be unhealthy. There is a biological reason for the symptoms – and often enough the treatment is a simple one.

Unfortunately, your doctor might miss that reason, especially if he or she relies too much on lab testing. That’s because lab tests are often misleading. Here’s an example:

If you look up these symptoms, you’ll find that your problem may be a deficiency of vitamin B12. Vitamin B12 is often deficient in people over 60. That’s because the enzyme systems that absorb B12 from your food often no longer work as you get older. So you go to your doctor and ask to have your B12 levels checked. And this is what your doctor may likely end up telling you.

“I am really surprised. Your symptoms sound just like a B12 deficiency, and you certainly are the right age to have one. But your blood levels are normal. It must be something else.” And off you and your doctor go looking for other causes when the truth is that all along you were both right. It was the lab test that was wrong.

This is one of the things that bugs me most about modern medicine. It relies way too much on lab tests. In fact, if your doctor can’t confirm a diagnosis by a test, then all too often, he or she deems that diagnosis wrong. The one who suffers is the patient. A recent article in the New England Journal of Medicine underlines just how bad this problem is.

Researchers at the New York Methodist Hospital in Brooklyn, NY found 23 patients who had been proven to have clear symptoms of B12 deficiency. Then they sent a blood sample from each patient to three separate labs to have the B12 levels determined. What they found shows you just how inaccurate tests can be. The first lab missed the diagnosis in 26% of the patients. The second one missed it in 22%. And the third one missed it in 35% of the cases. Consider how amazing this is.

It is very possible that doctors have completely misdiagnosed up to one-third of the patients out there who are suffering from B12 deficiency. They are doomed to be miserable for the rest of their lives simply because their doctors relied solely on blood tests instead of using their clinical skills.

One Surprising Cause of This Deficiency

One skill doctors should utilize more often is their ability to ask questions. And a very important question a doctor should ask a patient with symptoms of B12 deficiency is this: Are you a vegetarian?

I’ve written before about the problems with vegetarian diets. While they work great for some people, they definitely are not good for everyone. One reason is that it makes it particularly hard to get vitamin B12.

Vitamin B12 is incredibly important to our health. But it can be difficult to digest and absorb. So it’s vital you both consume it and absorb it. It’s a two-part equation. The good news is, unlike other B vitamins, your body can store B12 for long periods of time. If you don’t replenish the supply, though, you eventually will use up those stores. You’ll lose about 0.2% of your body’s stores per day. So, while the loss is slow, over time, months to years, you will become deficient. This happens to a lot of people who become vegetarians after eating animal-derived foods for many years.

Here’s why. While the bacteria in the intestines are capable of synthesizing vitamin B12, most people have to eat vitamin B12 in order to maintain high enough levels. And the best source of B12 is animal-derived foods. Animals do NOT make vitamin B12, contrary to popular myth. Nor do plants make it. Rather, bacteria are the primary manufacturers of this crucial vitamin. Most of it comes from bacteria in the soil. But the bacteria in your digestive tract (and that of animals) also make it.

Cows have loads of bacteria in their upper and lower intestines to break down the plant matter they eat. The large population of bacteria also means they have plenty of vitamin B12. The animal stores this B12 in its muscles and liver, the principle storage sites in mammals.

So when you eat animal products, including fish, you get B12. If you don’t eat animal-derived foods, it’s a lot harder to keep up the consuming side of the equation.

Carnivores and Omnivores Can Be Deficient Too

That said, even if you eat animal products, you still might have suboptimal B12 function. Your stomach acid separates B12 from the rest of the nutrients in your stomach. After your stomach acid frees it up, B12 must complex with a compound called intrinsic factor, another byproduct of the digestion process. If either of these steps is weak, missing, or incomplete, so will be your absorption of this critical nutrient.

After that, the B12-intrinsic factor complex journeys to the last part of your small intestine (terminal ileum). It’s there that specialized cells grab the complex for absorption.

Since seniors typically are deficient in stomach acid, they have a harder time absorbing B12. (People with pernicious anemia may lack both acid and intrinsic factor. They simply won’t be able to absorb B12 no matter how much they consume.)

So How Can You Tell If You Need B12?

There are a couple of ways. First, if your homocysteine levels are high, it’s quite possible you’re deficient. While B12 deficiency will cause your homocysteine to go up, it’s not the only cause of high homocysteine levels. Suboptimal folate and/or vitamin B6 could also raise homocysteine levels. So this isn’t the most reliable indicator.

The best test for functional vitamin B12 in your body is methylmalonic acid or MMA. MMA is a waste product. If you’re B12 deficient, your MMA levels will be high, as the B12 deficiency impairs your ability to get rid of the MMA. So MMA is the single best direct measurement of B12 activity in your body.

If you’re a vegetarian, over the age of 60, or have any kind of digestive problem, I suggest you get a yearly MMA test for B12 activity. Other symptoms include fatigue, loss of appetite, depression, cognitive problems, balance problems, and tingling and weakness in the legs and feet. I stand by this even if you take it orally as a supplement. Remember, it’s not what you take in, but what you absorb! The urine MMA test is probably the best single test for B12 deficiency. In one study, it was much more sensitive in identifying B12 deficient hospitalized patients than just examining blood levels. It found suboptimal B12 activity in 49% of a group of 35 seniors who had “normal” B12 levels in their blood. In vegetarians, 83% found to have suboptimal B12 activity had “normal” serum (blood) B12 levels.

This test is specific. If positive, you definitely have B12 deficiency. It will tell you if your B12 levels are back to optimum levels when the high MMA level is back down. But, despite how good the MMA test is, I don’t use it. I go on symptoms.

When a patient comes to me with symptoms suggestive of B12 deficiency, I don’t bother with tests. Even the MMA test is not perfect. Instead I just give them a B12 shot twice a week for four weeks.

I give it to them as an injection because I don’t have to worry about them properly digesting a pill. And because a shot will produce high tissue levels very quickly. If the patient’s symptoms go away, “Bingo,” there’s my diagnosis. If they don’t, then I can start looking elsewhere. But with this method, I never ever have to worry that I missed that critical diagnosis.

So, if you think you might be deficient, just tell your doctor to give you the shot and see how it works! The most effective form of B12 is methyl cobalamin. And the dose is 2 mg per injection.


Carmel, R. and Y.P. Agrawal. “Failures of cobalamin assays in pernicious anemia,” N Engl J Med, 2012; 367(4): 385-386.

October 2010: https://www.secondopinionnewsletter.com/Newsletter-Archive/View-Archive/1912/This-Vitamin-Deficiency-Doubles-Your-Risk-of-Alzheimers-and-Heart-Disease.html

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