Who Should Get B12 Injections?
People who will get the biggest benefits of B12 injections fall into these categories:
People with B12 deficiency due to malabsorption
B12 deficiency is notoriously tough to diagnose—the blood tests are prone to both false positives and false negatives (7)—and doctors don’t always agree on which combination of tests to use. Yet, B12 deficiency is clearly a problem: In the United States, it is estimated that roughly 6 percent of people under age 60 (8) are short on the micronutrient. That number rises to 1 in 5 in the over-60 population. There are also lots of people who land in the gray area, where they’re not clinically deficient, but don’t have adequate levels, either.
One of the most common culprits behind B12 deficiency is malabsorption, where a step in the breakdown and absorption of B12 goes awry, preventing your system from soaking it up. In these cases, even the largest oral dose won’t significantly spike your levels, since your body is unable to utilize the vitamin. That makes injections your best bet if you’re dealing with…
1. Pernicious anemia
With pernicious anemia—a frequent cause of B12 deficiency—autoimmune activity destroys the intrinsic factor protein or the cells that make IF, which means the ileum of affected folks can’t absorb the vitamin. “You want to be sure the B12 gets into the body,” says Green. “The surefire way of doing that is by injecting into the muscle.”
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2. Atrophic gastritis
Loss of stomach acid, usually seen in older adults, can result in a condition called atrophic gastritis, says Miller. With reduced stomach acid to break down your food, you may not be able to access the B12 embedded in your burger.
3. Bariatric surgery
Restricted stomach = reduced B12. “When you bypass the stomach or put a band around the stomach, or any of these various surgical procedures to reduce weight, you diminish the capacity to absorb B12,” says Green. Or as Miller puts it, “You’ve essentially made the person equivalent of having pernicious anemia.” That’s because these surgeries can reduce the production of both intrinsic factor and stomach acid, which is necessary for digesting food. These patients may only need a handful of injections to restore their B12 levels, which can then be maintained with a high-dose supplement or scheduled injections.
4. Certain medications
Two classes of drugs—proton-pump inhibitors (e.g. Nexium and Prilosec) and H2 blockers (e.g. Zantac and Pepcid)—may interfere with B12 absorption after long-term use, since they lower the acidity of the stomach.
Another potential B-enemy: metformin (a medication taken by diabetics to control blood sugar levels). Studies have shown that long-term use of metformin may be associated with B12 deficiency.
Although taking these meds doesn’t automatically equal deficiency, your doctor should keep an eye on your B12 levels, especially if you’ve been taking acid-blockers for longer than a year or metformin for more than four months, according to an article in the journal, American Family Physician (9).
5. Autoimmune digestive diseases
Crohn’s disease can affect the absorption of B12, since the ileum is often affected, according to British researchers (10). Celiac disease can also lead to malabsorption because the intestinal villi, the finger-like protrusions that absorb nutrients, can begin to atrophy, Dutch scientists (1) say.
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People who don’t eat enough B12-rich foods
Non-meat-eaters don’t have a problem absorbing B12—they just don’t consume enough of it. That means vegans and vegetarians may respond well to B12 supplements or injections.
