More and more, ours is a worn out, sleep-deprived, distracted nation. It’s no wonder a shot of energy and focus would appeal to many of us. And that’s exactly what B12 injections deliver—literally—for those who lack sufficient stores of the nutrient.
“B vitamins are essential for proper cellular respiration,” explains Dr. Roxanne Sukol, medical director of Cleveland Clinic’s Wellness Enterprise. Without adequate supplies of B12, most of the cells in your body will struggle to take in enough oxygen, which can affect everything from your energy levels to your mood and concentration, Sukol says. Classic symptoms of a B12 deficiency also include diarrhea or constipation, pale skin, and shortness of breath, according to the National Institutes of Health.
The nutritional necessity of B12 explains why it’s such a popular supplement, and also why some celebrities have touted B12 injections as the magic ingredient in their health regimens. The vitamin’s links to increased energy have also made B12 popular among some dieters and weight loss clinics—the thinking being that more energy will translate to more exercise.
“But unless you have a B12 deficiency, there’s really no role for it,” Sukol says of B12 shots and supplements. Put simply, more isn’t better. And even if you’re low on B12, there’s no evidence injections of it will help you lose weight, says Dr. Brent Bauer, director of the complementary and integrative medicine program at Mayo Clinic. “Everybody’s looking for a shortcut,” he says. “B12 supplementation has its benefits, but it’s not a solution for weight loss.”
So weight loss is out, but B12 shots have been associated with other conditions, too. In fact, there’s some solid research on B12 injections for the treatment of fibromyalgia and myalgia encephalomyelitis.
Food sources of the vitamin include eggs, meat, and dairy products. People who eschew those foods are at elevated risk. “When I test vegans for B12, they’re usually on the low side—if not deficient,” Sukol says. Some gut-related diseases like Crohn’s or Celiac—as well as most types of weight loss surgery—can also limit the amount of B12 your system absorbs, she adds.
But figuring out if you’re low on B12 is trickier than you might suppose. A much-cited 2000 study from the American Journal of Clinical Nutritionfound nearly 40% of the population have B12 levels that fall at or below what experts consider the low end of normal. While you might assume anything in the “normal” range means you’re in good shape, Sukol says that’s not always the case.
“Blood tests are not always black and white the way we’d like them to be,” she says. “If I have a patient taking a lot of naps and complaining about poor concentration, I might recommend B12 supplementation even though the blood tests look normal.”
You’ll notice she says “supplementation” and not “injections.” Unless you have one of the above conditions that prevent your gut from breaking down and absorbing the vitamin, a B12 pill is as effective as a B12 poke, research suggests. Sukol agrees. “For many people, an oral supplement is just as good [as an injection].”
Finally, when it comes to the safety of both B12 injections and oral supplements, you don’t have much to worry about. “B12 is water soluble, and it’s generally safe even at very high doses,” Bauer explains. “You put a needle in your arm and there’s always the risk of swelling or pain at the site, but in the complementary medicine realm B12 is probably one of the safest things you could take.”
If you’re often worn out or foggy brained, even after a good night’s sleep, “take a B12 supplement for a week or two and see how you feel,” Sukol advises. If your fatigue persists, have your blood tested for nutrient deficiencies.
A B12 shot may be just what your doctor orders.
This article originally appeared on Time.com.