Always tired? What you should know about B12 and whether it really raises energy

Med spas are promoting vitamin B12 injections as a quick energy fix. But do they really make you feel more alert?

If you spend time on social media, you may have seen med spa owners and staff describe vitamin B12 shots as a way to perk up. When they feel drained or are heading into a packed week, they say a fast injection helps them get by. Some spas claim people notice a boost in energy within a day or two and suggest repeating the shot every few weeks.

B12 is vital for health, and a shortage can leave people feeling worn out or worse. But most people already get enough B12, and for them, extra doses are unlikely to do much.

Here’s what to know about what B12 does, who may become deficient and when testing makes sense.

What is vitamin B12?

Vitamin B12 occurs naturally in animal-based foods such as meat, fish, eggs and dairy, and it is added to some breakfast cereals and nutritional yeast. It helps the body make red blood cells and DNA, and it supports proper nerve function. It also helps convert food into energy, which is why it has a reputation as an energy booster.

When people do not get enough B12, they may develop anemia, memory problems, depression and fatigue, says Andrea Dean, a hematologist at Loyola University Medical Center in Chicago. If levels are very low, numbness and tingling in the hands and feet can also appear.

Why do some people run low on B12?

Eating foods that contain vitamin B12 does not guarantee adequate levels. To absorb the vitamin, the stomach must produce enough acid and a protein called intrinsic factor.

When B12 deficiency shows up despite a balanced diet, it is often linked to a condition that lowers stomach acid production, such as gastritis, or to pernicious anemia, an autoimmune disorder in which the stomach stops making intrinsic factor.

About 4% of US adults have low B12 levels, and deficiency is more common in people age 60 and older. Other risk factors include weight-loss or stomach surgery, digestive disorders such as celiac disease or Crohn’s disease, and heavy alcohol use.

Long-term use of metformin for diabetes or acid-reducing medications can also lower B12 levels. Vegans and some vegetarians can become deficient as well unless they eat fortified foods or take supplements.

Does taking B12 improve energy levels?

For people whose fatigue or mental sluggishness is caused by low B12, treating the deficiency can bring energy back. But if levels are already normal, getting more B12 will not make someone feel less tired or improve athletic performance. Dean compares it to filling a car with gas: if the tank is already full, more fuel will not make the car go faster.

Some people who feel better after a B12 shot may be responding to a placebo effect. “We know that some of this is just all mental,” says Dean. For med spa owners who recommend the injections, there is also a financial incentive: the shots cost a typical US spa less than $1 each and are sold to consumers for $25 to $75 apiece. Profits grow when patients return weekly.

Spas that sell these injections face little risk. B12 is generally safe, even in high doses, because the body eliminates what it does not need, and Dean says she has never seen anyone overdose on it. Still, if B12 levels are normal, the injections are unlikely to be worth the price.

When should I get my B12 levels tested?

Fatigue can have many causes, including poor sleep, low thyroid hormone and low iron. “It’s not just B12,” says Dean. So if you feel tired most of the time, it is worth seeing a clinician who can help identify the cause.

A B12 test is a simple blood draw that a primary care doctor can order. In many US states and in the UK, it is also possible to order one online through commercial labs. Even so, the results can be hard to interpret on your own, because deficiency can exist even when the number looks normal. Most labs consider levels low at less than 200 or 250 pg/mL, but Dean treats anyone below 400 pg/mL. For people with borderline results and symptoms, doctors can order two additional blood tests, methylmalonic acid and homocysteine, to help confirm a deficiency.

If your level is low, your doctor should also look for the reason, since the cause affects treatment. Sometimes the medical history provides the answer; otherwise, your doctor may test for pernicious anemia.

How is B12 deficiency treated?

B12 can be taken as a pill or given as an injection. Shots deliver the vitamin into a muscle or under the skin, bypassing the gut completely.

That makes injections the better option for people with severe deficiency, nerve symptoms or conditions such as pernicious anemia that interfere with absorption. When nerve symptoms are present, “we don’t play around,” says Dean.

For many other people, pills work just as well. High-dose oral B12 raises blood levels about as effectively as injections, and it costs less.