Box of 10 x 1ml ampoules dosed at 1500mcg of b12
A deficiency in vitamin B12 can lead to various health problems, ranging from fatigue to permanent neurological changes.
If a person has low vitamin B12 levels due to a health condition, a doctor may recommend oral supplementation or injections of the vitamin.
How Do B12 Shots Differ From Supplements?
There are lots of over-the-counter forms of B12 to choose from, including pills, lozenges, and sublingual tablets. There’s also a prescription B12 nasal spray.
If you opt for oral supplements, your body absorbs the B12 in your G.I. tract—similar to how it’s processed when food is your source. This uptake depends on a protein called intrinsic factor (IF), which captures B12 in the small intestine, absorbing it in the final stretch of your small intestine (the ileum).
If you have a healthy digestive system, you’ll very efficiently absorb the first two micrograms of an oral dose (about 70 to 90 percent of it), says Green; after that, you’ll take in a small additional amount as it diffuses across the mucus membranes of your G.I. tract. However, if you lack IF (the case for people with pernicious anemia; see below), your small intestine can’t absorb supplemental or dietary B12, so you’ll only glean a small fraction (about 1 to 2 percent) of the dose.
With sublingual or intranasal B12, the vitamin seeps through the linings of your mouth, nose, or G.I. tract. That means you’ll only capture 1 to 2 percent of the dose (as mentioned above), making this an inefficient way to increase your B12 levels.
The Benefits of B12 Injections
Here are some benefits of B12 injections you may notice:
Improved Mood
Evidence has linked depression with B12 deficiency. So if you’re short on the nutrient, the shots may help normalize your mood. Of course, if you’re depressed, Miller emphasizes, you shouldn’t self-medicate with any supplement, B12 included. Make seeing your healthcare professional a priority, and while you work toward a diagnosis, you can ask your provider to prescribe B12 injections.
Bone Health
If your body lacks B12, your skeleton may suffer: in a study published in the Journal of Bone and Mineral Research (4), low B12 was linked with poor bone mineral density, suggesting a role for the vitamin in bone formation. Older folks who are deficient may also be at higher risk of osteoporosis and hip fractures (a known complication of pernicious anemia). However, as Miller says, the research linking B12 with bone health only shows an association, not a cause-effect relationship.
Increased Energy
If you’re fatigued due to deficiency, B12 shots may help recharge your battery. Fatigue may be a problem for those in particular with pernicious anemia, a cause of low B12. Pernicious anemia develops when your body cannot make enough healthy red blood cells because it doesn’t have enough vitamin B12. This can lead to low energy levels. See below for more on whether non-deficient folks should consider B12 shots to improve their energy.
Memory Maintenance
Don’t forget your B12. “Normal B12 status is important in the preservation of normal cognitive function,” says Green. In fact, people with vitamin B12 levels on the lower side of normal performed worse on memory tests than those with high-normal levels in a study in The American Journal of Clinical Nutrition (5). Even after age differences were accounted for, the effect on memory remained. Why? Inadequate B12 has been associated with degeneration of neurons and atrophy of your brain’s gray matter, which is critical for information processing.
Memory loss is one symptom you don’t want to neglect: “The neurologic complications of B12 deficiency are often reversible, but not always,” warns Green.
