Vitamin B12 Injections – Benefits, Side Effects, & Alternatives

Vitamin B12 is an essential vitamin, which we needed for vital processes like energy production and metabolism. Unfortunately, almost 15 percent of the population in the US has vitamin B12 deficiency or suboptimal levels of B12 in their body (1).

It is common in people who take stomach acid altering medicines, antibiotics, the elderly, and vegans.


Luckily, advances in medical technology have made it easier to deal with such medical problems. Vitamin B12 injections are used to offset the symptoms of vitamin B12 deficiency like fatigue, weakness, poor moods and low concentration.

Unfortunately, they also have some risks and disadvantages. These injections are not able to resolve the underlying cause of the deficiency.

Read on to learn more about the advantages of vitamin B12 injections and their drawbacks.

What is vitamin B12?

Vitamin B12, also known as cobalamin, is a water-soluble vitamin. Vitamin B12 is the largest and most structurally complicated vitamin.

It is naturally found in animal products like fish, meat, eggs, and dairy products. It plays a vital role in nerve tissue health, brain function and the production of red blood cells.

Our body can store vitamin B12 for up to four years. So, it usually takes years for vitamin B12 deficiency to develop.

Recommended intake

According to the Food and Nutrition Board (FNB), the recommended dietary allowances for vitamin B12 are (2) –

0 to 6 months0.4 mcg0.4 mcg  
7 to 12 months0.5 mcg0.5 mcg  
1 to 3 years0.9 mcg0.9 mcg  
4 to 8 years1.2 mcg1.2 mcg  
9 to 13 years1.8 mcg1.8 mcg  
14 + years2.4 mcg2.4 mcg2.6 mcg2.8 mcg


What causes vitamin B12 deficiency?

Vitamin B12 is found in animal foods. So this deficiency is more common in people who follow vegan or vegetarian diets (3).

Some meat eaters are also unable to absorb vitamin 12 well. Vitamin B12 needs a protein known as the intrinsic factor for absorption. The intrinsic factor binds with vitamin B12 so that it can be absorbed in the blood.

People who have had intestinal surgery or weight loss surgery are unable to absorb vitamin B12. People with diseases like Crohn’s disease and celiac disease are also at a higher risk of B12 deficiency.

The elderly are also at risk for vitamin B12 deficiency as their ability to absorb vitamin B12 decreases with age (4).

Symptoms of vitamin B12 deficiency

  • Chronic fatigue syndrome, weakness, and lethargy
  • Joint pain and muscle fatigue
  • Cognitive problems, memory issues and inability to concentrate
  • Anxiety and depression
  • Rapid heartbeat and palpitations
  • Bleeding gums and mouth sores
  • Poor appetite and digestive issues like constipation, nausea, diarrhea, and cramping
  • Higher risk of developing different cancer and heart problems

What are vitamin B12 injections and how do they work?

Vitamin B12 deficiency can lead to health issues like pernicious anemia and neurological problems. Vitamin B12 injections are an effective way to treat this deficiency.

Vitamin B12 injections are shots of hydroxocobalamin or cyanocobalamin. They are useful in elevating the levels of vitamin B12 in the body and reversing the deficiency.

They are prescribed by the doctor and are administered into the patient’s muscle tissue once a month.

Vitamin B12 Injections info

Benefits of vitamin B12 injections

1. May improve brain function

Deficiency in vitamin B12 has been linked to a decline in brain function. According to a review of several studies, low serum vitamin B12 levels are associated with neurodegenerative disease and cognitive impairment (5).

Studies have shown that supplementing with vitamin B12 can prevent depression, restore a better mood and retain a good memory (6).

2. Helps deal with chronic fatigue syndrome

Vitamin B12 injections help in managing chronic fatigue syndrome. The injections help the patients relieve fatigue and improve their sleep patterns. These shots of methylcobalamin also contain folic acid, which helps in reducing pain.

3. Improves metabolism

Vitamin B12 injections can help improve sluggish metabolism and aid in weight loss. These injections lead to a boost in energy which helps the body in the production and regulation of hormones.

It also helps in improving sleep and exercise performance.

4. May prevent diseases

Many studies have shown that regular vitamin B12 shots can help boost the body’s defense mechanism. Weekly B12 shots can prevent cancers of the lung, prostate, colon, and breast.

5. Prevents osteoporosis

Osteoporosis leads to loss of bone mass and an increased risk of bone fractures. Deficiency in vitamin B12 causes a reduction in bone mass (7). These findings suggest that increasing the levels of vitamin B12 can help reduce the risk of osteoporosis.

6. Prevents age-related macular degeneration

Several observational studies have indicated a direct link between vitamin B12 and age-related macular degeneration. During one extensive investigation, researchers gave 5442 women over the age of 40 a combination of folic acid, pyridoxine hydrochloride, and cyanocobalamin for 7.3 years.

The study found a 35 percent lower risk for age-related macular degeneration among the women who took the supplement (8).

7. Protects the heart

Elevated homocysteine levels increase the risk of cardiovascular disease. Vitamin B12 is vital for the conversion of homocysteine and therefore prevent heart attack, stroke, and coronary heart disease.

8. Improves hair, nails, and skin

Adequate amounts of vitamin B12 also help in keeping the hair, nails, and skin healthy. It helps deal with dryness, acne and skin blemishes.

It improves the condition of the hair and makes it shiny and healthy. Nails also become stronger when you start taking vitamin B12 injections.

9. Helps with fetal development

Adequate levels of vitamin B12 are essential for proper fetal development during pregnancy. A lack of this essential vitamin can result in mental retardation, neurological and ocular disorders and failure to thrive.

It is necessary to recognize these errors of cobalamin absorption and treat it as soon as possible (9).

Side effects of vitamin B12 injections

Vitamin B12 injections are generally considered safe, and they have no significant side effects. However, in some rare cases, they can cause allergic reactions and sensitivity.

1. Pain and redness

Some people may experience pain, redness, itching at the sight of the injection. Some people may also experience slight swelling all over the body and diarrhea.

2. Low potassium levels

This injection can also cause low levels of potassium in the blood (hypokalemia), which can lead to muscle cramps, weakness, and irregular heartbeat.

3. Problems with absorption

Even if you do receive a B12 injection, this does not mean that your body will be able to absorb all of the B12. The utilization of the B12 in the body depends on metabolic cofactors and acids.

Due to the limitations of the stomach acid and intrinsic cofactor, only a limited amount of the supplement is absorbed into the body.

Is it dangerous to take too much vitamin B12?

Vitamin B12 is a water-soluble vitamin, which means that any excess amount will be flushed out by the body. According to the Institute of Medicine, excess vitamin B12 intake from food or supplements has no adverse effects (10).

Also, if you are not deficient in vitamin B12, to begin with, the B12 injection will not have much impact.

Better ways to get vitamin B12

Vitamin B12 is available in animal food and food that is fortified with B12. It is always healthier to get any nutrient from its natural source. So, try to include these foods in your diet to get the maximum benefit of this nutrient.

These foods are some of the excellent sources of vitamin B12:

  • Liver: A 75 grams serving provides 881% of the RDI
  • Beef Kidney: A 75 grams serving provides 311% of the RDI
  • Trout: A 75 grams serving provides 61% of the RDI
  • Canned salmon: A 75 grams serving provides 61% of the RDI
  • Ground beef:  A 75 grams serving provides 40% of the RDI
  • Eggs: Two large eggs provide 25% of the RDI
  • Milk: A 250 ml serving provides 20% of the RDI
  • Chicken: A 75 grams serving provides 3% of the RDI

It can be particularly tough for vegetarians and vegans to meet their daily requirement for vitamin B12. These people can take vitamin B12 shots or supplements.

Many recent studies have shown that B12 supplements are as effective as injections for raising blood levels (10).

Final thoughts

Vitamin B12 helps the body in using fats and carbohydrates for energy. It plays a vital role in brain function, production of DNA and red blood cells.


A deficiency in vitamin B12 can lead to neurological damage, heart problems, fatigue, muscle weakness, joint pain, and hormone imbalance.

The best way to get vitamin B12 is through a nutritious and healthy diet that includes liver, beef kidney, trout, salmon, eggs, and milk.

However, this may be difficult for vegetarians, people with specific ailments, and the elderly. For them, vitamin B12 injections can be used to overcome the B12 deficiency.

Though these injections have many benefits, they can also cause an allergic reaction in some people.  There is also a possibility that you may be taking unnecessarily large amounts that may not get absorbed by the body.


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