If you spend time on social media, you may have seen med spa owners and employees describing vitamin B12 shots as a pick-me-up. When they’re run down or facing a busy week, they say, a quick injection gets them through. Some med spas say many people feel an energy lift within a day or two and recommend a shot every few weeks.
B12 is essential to your health, and people who don’t get enough of it can feel exhausted or worse. But most people already have plenty of B12, and for them, extra doses aren’t likely to help.
Here’s what you need to know about what B12 does, who runs low on it and when to get tested.
What is vitamin B12?
Vitamin B12 is found naturally in animal foods like meat, fish, eggs and dairy, and it’s added to some breakfast cereals and nutritional yeasts. It helps your body make red blood cells and DNA, and it keeps your nerves working properly. It also plays a role in turning food into energy, which is where its reputation as an energy booster comes from.
When people don’t have enough B12, they can develop anemia, memory problems, depression and fatigue, says Andrea Dean, a hematologist at Loyola University medical center in Chicago. If their levels are seriously low, they can also develop numbness and tingling in their hands and feet.
Why do some people run low on B12?
Eating foods rich in vitamin B12 isn’t enough to ensure you have adequate levels. To absorb this vitamin, your stomach needs to produce adequate acid, along with a protein called intrinsic factor.
When people have B12 deficiencies despite a balanced diet, it’s often because they have a condition that reduces stomach acid production (like gastritis) or pernicious anemia, an autoimmune condition in which the stomach stops making intrinsic factor.
About 4% of US adults have low B12 levels, and deficiency is more common in adults 60 and up. Other factors that raise the risk include having weight loss or stomach surgery, digestive conditions like celiac or Crohn’s disease and overusing alcohol.
Taking the diabetes drug metformin or acid-reducing medications for a long time can also lower B12 levels. Vegans and some vegetarians can become deficient too, unless they eat fortified foods or take a supplement.
Does taking B12 improve energy levels?
For people who feel fatigue or mental slowing due to low B12 levels, treating the deficiency can restore their energy. But if your B12 levels are already adequate, getting more won’t make you feel less worn out or improve your athletic performance. Dean compares it to filling up a car: if the gas tank is already full, adding more gas won’t make the car go faster.
Some people who feel more energetic after a B12 shot may be experiencing a placebo effect. “We know that some of this is just all mental,” says Dean. For med spa owners who endorse the injections, it’s also financial: The shots cost a typical US spa less than $1 a piece and are sold to consumers for $25 to $75 each. The profits add up when patients get weekly shots.
There’s not much risk to spas who sell these shots. B12 is generally safe, even at high doses, because your body gets rid of what it doesn’t need, and Dean says she has never seen anyone overdose on it. But if your B12 levels are normal, injections are unlikely to be worth their cost.
When should I get my B12 levels tested?
Fatigue has many possible causes, including poor sleep, low thyroid hormone and low iron. “It’s not just B12,” says Dean. So if you’re tired most of the time, it’s worth seeing a clinician who can look for the cause.
A B12 level is a simple blood test that your primary care doctor can order. In many US states and the UK, you can also order one yourself online through commercial labs. However, the results can be tricky to interpret on your own because you can be deficient even when your result looks normal. Most labs consider levels to be low if they’re less than 200 or 250 pg/mL, but Dean treats anyone with a level below 400 pg/mL. For people with borderline levels and symptoms, doctors can order two more blood tests, called methylmalonic acid and homocysteine, to help confirm a deficiency.
If your level is low, your doctor should also figure out why, because the cause affects how it’s treated. Sometimes your medical history explains it, but otherwise, your doctor may test you for pernicious anemia.
How is B12 deficiency treated?
B12 can be taken as a pill or given as a shot. Shots deliver the vitamin into a muscle or under the skin, which skips the gut entirely.
That makes shots the best choice for people with severe deficiency, nerve symptoms or conditions like pernicious anemia that keep them from absorbing B12. When someone has nerve symptoms, “we don’t play around,” says Dean.
For many others, pills work just as well. High doses of oral B12 raise blood levels about as effectively as injections, and they cost less.
