Vitamin B12 shots are injections that a doctor may prescribe to treat a vitamin B12 deficiency. They may be useful for those with gastrointestinal issues, older adults, vegans, and vegetarians.
Vitamin B12 injections are usually for people with bodies that have problems absorbing vitamin B12 and those who have undergone gastric surgery. This is because shots enable the body to absorb vitamin B12 without going through the digestive system.
This article addresses the importance of maintaining adequate vitamin B12 levels and outlines the benefits and risks associated with vitamin B12 shots.
Vitamin B12 is an essential water-soluble vitamin that plays a role in many bodily functions, including:
- DNA production
- red blood cells
- nerve cells
Without vitamin B12, a person may feel tired and weak due to megaloblastic anemia.
Vitamin B12 is present in
- dairy products
- nutritional yeast
- some fortified foods
Vitamin B12 shots are a form of supplementation that contains a synthetic version of vitamin B12, or cyanocobalamin. A doctor will inject the shot into the muscle. If they inject it into a vein, the body may lose a high proportion as the person passes urine.
Cyanocobalamin is available in liquid, tablet, and capsule form. Certain foods, such as cereals, may be fortified with the synthetic form of vitamin B12.
How long do vitamin B12 shots last?
How often a person will require shots depends on what is causing their B12 deficiency. Initially, a person may need B12 supplementation shots every day for around two weeks or until symptoms improve.
If the cause of a person’s B12 deficiency is their diet, they may not require further shots or only require them once or twice per year.
In cases where a chronic condition is causing a deficiency, people may require B12 shots around every 2 months.
Vitamin B12 shots are only available by prescription following a clinical diagnosis of low levels. However, low levels
Some people’s bodies do not produce enough stomach acid or intrinsic factor if they have a condition known as autoimmune atrophic gastritis. These people may need vitamin B12 shots to reduce their risk of deficiency, which can lead to pernicious anemia.
Other people needing shots include those who have had gastrointestinal surgery if their digestive system cannot absorb vitamin B12 efficiently.
People with symptoms of vitamin B12 deficiency
Anyone with signs and symptoms of a vitamin B12 deficiency or pernicious anemia should consult a doctor.
Signs and symptoms include:
- difficulty thinking and remembering
- heart palpitations
- pale skin
- weight loss
- numbness and tingling in the hands and feet
Vitamin B12 deficiency risk factors
The following risk factors can increase the chance of developing vitamin B12 deficiency:
- high alcohol consumption
- older age
- pernicious anemia
- atrophic gastritis, which refers to inflammation in the stomach
- Helicobacter pylori infection
- celiac disease
- Crohn’s disease
- a history of gastrointestinal surgery
- following a plant-based diet
- pancreatic insufficiency
- some hereditary conditions that affect vitamin B12 absorption
People with gastrointestinal issues
Conditions that affect the gastrointestinal tract may affect vitamin B12 release or absorption.
- pernicious anemia, which can lead to gastric atrophy, or damage to the stomach
- fish tapeworm infestation
- bowel or pancreatic cancer
- folic acid deficiency
- overgrowth of bacteria in the small intestine
- celiac disease
- Crohn’s disease
Individuals who have undergone gastrointestinal surgery, including weight loss, may have fewer cells necessary to secrete stomach acid and intrinsic factor. This can also affect vitamin B12 absorption.
Vegetarians and vegans
Vitamin B12 mainly occurs in animal foods, so people who follow a plant-based diet have a higher risk of vitamin B12 deficiency.
In rare cases, a doctor may recommend injections, but
Vegetarian or vegan people who are pregnant may
Discover the best vegan and vegetarian sources of B12 here.
|0–6 months||0.4 micrograms (mcg)|
|7–12 months||0.5 mcg|
|1–3 years||0.9 mcg|
|4–8 years||1.2 mcg|
|9–13 years||1.8 mcg|
|14+ years||2.4 mcg|
|Pregnant people||2.6 mcg|
|People who chestfeed||2.8 mcg|
However, a doctor can advise on an individual’s specific needs.
A doctor may recommend vitamin B12 shots for people at risk of a deficiency or its complications.
Vitamin B12 shots may help reduce the risk of the following conditions:
There is no upper limit for the intake of vitamin B12 because the risk of toxicity or overdose is low. However, vitamin B12 shots may have other side effects.
After having a B12 shot, a person should monitor for adverse symptoms and seek medical help if they experience:
- severe pain at the injection site
- mild diarrhea
- a swelling sensation in the body
- temporary itching of the skin
In rare cases, a person may also be at risk of:
- pulmonary edema
- congestive heart failure
- peripheral vascular thrombosis, which involves blood clots
- polycythemia vera, which is a type of blood cancer
Medications side effects
Some other prescription medications can directly cause a vitamin B12 deficiency.
- H2 receptor antagonists
- proton pump inhibitors
Allergies and medical conditions
Those with allergies or medical conditions should always inform a doctor before receiving a vitamin B12 shot. Vitamin B12 shots may not be suitable for people with a history of:
Most people get enough vitamin B12 from their diet, but some people have a deficiency. This can be due to having low levels of intrinsic factor in the digestive system, having a digestive condition, or following a plant-based diet.
If dietary sources are insufficient, however, a doctor may recommend supplementation through pills or injections, depending on the cause of the deficiency.