Vitamin B12 injections, also known as hydroxocobalamin or cyanocobalamin, are used to treat B12 deficiency caused by conditions like pernicious anemia, Crohn's disease, and atrophic gastritis.

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.

Here are some key points about B12 injections:

• Purpose: To treat B12 deficiency and reduce the risk of certain health disorders.

• Administration: Given intramuscularly (into the muscle)

• Types: Usually hydroxocobalamin or cyanocobalamin.

• Weight Loss: B12 shots are believed to assist in weight loss efforts.

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 are rare in most healthy adults because the human liver stores vitamin B12 over time.

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.

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

• fatigue

• heart palpitations

• pale skin

• weight loss

• infertility

• numbness and tingling in the hands and feet

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:

• heart disease

• stroke

• neurological disorders

• problems with thinking and memory

• vision loss

• infertility

• neural tube defects in children born to those with a vitamin B12 deficiency

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:

• anaphylaxis

• pulmonary edema

• congestive heart failure

• peripheral vascular thrombosis, which involves blood clots

• polycythemia vera, which is a type of blood cancer

If anyone experiences difficulty breathing, hives, and swelling, they need emergency medical help. They may be experiencing anaphylaxis, which is a severe allergic reaction

Vitamin B12 may interact with certain medications. People must always inform a doctor about all prescription and over-the-counter drugs before receiving a vitamin B12 shot.

Some other prescription medications can directly cause a vitamin B12 deficiency. These include":

• H2 receptor antagonists

• metformin

• 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:

• sensitivity to vitamin B12

• Leber’s disease, which affects the optic nerve

• kidney problems

• hypokalemia, or low potassium levels

• deficiencies in other nutrients, particularly folic acid and iron

Vitamin B12 injections provide the individual with a synthetic version of vitamin B12. A doctor may recommend vitamin B12 shots if a person has a vitamin B12 deficiency.

Vitamin B12 injections typically begin to work straight away. However, it may take a number of days or weeks before a person notices improvements in their symptoms.

Precautions a person may need to take after receiving a B12 injection may depend on which side effects they experience.

For example, if they experience dizziness, they should avoid driving.

A person’s doctor can provide them with information about any specific activities they may need to avoid or any other considerations.

This might include limiting alcohol intake.