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B12 Shot Side Effects – Do The Benefits Outweigh The Risks?

Sep 6, 2020
B12 Shot Side Effects – Do The Benefits Outweigh The Risks?

Vitamin B12 continues to gain popularity and attention. Many people want to know what are the vitamin B12 side effects and benefits. Are Vitamin B12 injection side effects greater or worse than oral B12 side effects? Does it even make a difference? While this treatment still fascinates us today and poses many questions, the history of the development of vitamin B12 is just as interesting.

In the 1850s, pernicious anemia was essentially a fatal condition – in today’s medicine, pernicious anemia is easily treated with B12 supplements. However, in the 1850s, patients suffered from abnormal gait and exhaustion, and inevitably they ended up in the hospital before they passed. 

It wasn’t until the 1920s when Georges Richard Minot and William Parry Murphy determined that certain foods (red meat and liver) effectively treated anemia in dogs. Almost 50 years later, organic chemist Robert Woodward successfully synthesized vitamin B12. From this discovery, modern medicine created treatments based on the discovery of vitamin B12’s role in anemia and the successful synthesis of its complex structure.

Thankfully, conditions caused by vitamin B12 deficiencies are incredibly treatable through vitamin B12 supplements. Understanding the B12 shot side effects and benefits can help you manage your expectations of vitamin B12 as a treatment and whether a B12 shot it the best form of treatment.

Vitamin B12 – What It Is And What It Does

Vitamin B12, also known as cyanocobalamin, is an important factor in DNA synthesis, the metabolism of every cell within the body, the maturation of developing red blood cells, and the metabolism of fatty acids and amino acids. 

Because vitamin B12 is such an integral component in the function of a healthy body, maintaining the proper levels of B12 within the body is necessary to sustain a properly working nervous system and a healthy red blood cell count.

Vitamin B12 is most commonly sourced through foods that come from animals such as fish, red meat, eggs, dairy, cheese, and other dairy products. Those who are vegan or vegetarian sometimes source their B12 through fortified cereals. 

While many people can consume and absorb the proper amount of vitamin B12 through their dietary choices, many people cannot sustain the proper levels of B12 within their bodies, which can lead to dangerous conditions if left untreated.

Vitamin B12 deficiencies are rare in otherwise healthy individuals; however, those at an elevated risk at groups who do not consume a diet with animal-sourced food, as well as those suffering from other health conditions. Groups at an increased risk of developing a vitamin B12 deficiency are:

  • Vegans
  • Vegetarians
  • Adults over 50
  • Those with low gastric intrinsic factor
  • Those with a low amount of stomach acid
  • Those taking certain medications
  • Gastrointestinal disorders like Crohn’s disease and celiac disease
  • Those who have had weight loss surgery, bowel resection, or surgery on another part of the digestive tract
  • Those who take metformin and acid-reducing medications
  • Those with specific genetic mutations, such as MTHFR, MTRR, and CBS
  • Those who regularly consume alcoholic beverages (NIH, n.d.)

If someone fits into one of these at-risk groups, it is best to consult your doctor to consider whether you should undergo testing to determine if you have a vitamin B12 deficiency. 

Presently, no one test determines whether or not someone is deficient in vitamin B12. Doctors must consider both lab results and clinical conditions to reach a diagnosis.

B12 Shot Side Effects – Do The Benefits Outweigh The Risks?

Symptoms Of B12 Deficiency

Before considering both the B12 shot side effects, and the B12 shot benefits, it is important to understand the symptoms of a vitamin B12 deficiency. Individuals cannot procure vitamin B12 without a prescription, and to obtain a prescription, you must be deemed deficient. 

It can be especially tricky to reach this diagnosis as there is no “gold-standard” test, and symptoms can long go unnoticed or be contributed to other causes.

Consider that vitamin B12 is responsible for many bodily functions; the displayed symptoms and affected body systems can vary greatly. Another problem is that symptoms and their onset tend to increase gradually, again making it hard to connect the dots between symptoms and causes. Listed below are just a few of the symptoms caused by a vitamin B12 deficiency:

  • Abnormal reflexes
  • Tingling, numbness, or other neuropathies
  • Impaired sense of position
  • Weakness in arms or legs
  • Dizziness, vertigo, or balance issues
  • Difficulty walking or abnormal gait
  • Confusion or memory loss
  • Dementia
  • Restless legs
  • Tremors
  • Vision problems
  • Incontinence
  • Impotence
  • Anger and irritability
  • Depression
  • Personality changes
  • Paranoia
  • Mania and/or psychosis
  • Hallucinations
  • Violent and antisocial behavior
  • General weakness
  • Shortness of breath or difficulty breathing
  • White appearance; pallor
  • Fatigue or general tiredness
  • Anemia
  • Coordination and balance problems while walking
  • Difficulty focusing
  • Memory loss
  • Sleep issues
  • Hair loss
  • Constipation
  • Loss of appetite
  • Swollen tongue.
  • Fast heart rate
  • Shortness of breath
  • Mouth pain
  • Irritability
  • Nausea
  • Vomiting
  • Diarrhea
  • Weight loss

Keeping an eye out and paying close attention to these symptoms can help in accurately diagnosing a vitamin B12 deficiency. If you think you may be deficient in vitamin B12, it is important to contact a health care professional and schedule a consultation.

Treatment For Vitamin B12 Deficiency

Fortunately, modern medicine has many options to safely and successfully treat vitamin B12 deficiency. There are three main treatment methods – a change in diet, oral supplements, and vitamin B12 injections. 

Those who aren’t receiving enough vitamin B12 due to food choices may be able to treat their deficiency by incorporating more vitamin B12 rich foods into their diets.

However, for those deficient as a result of age, a genetic mutation, stomach issues, or those taking certain medications, a change in diet may not be enough to treat a vitamin B12 deficiency. 

These individuals will likely have to supplement their diet with an oral B12 supplement or a B12 injection. Oral supplements are considered inferior to vitamin B12 injections as they take longer to absorb, and some of the nutritional value is lost during digestion in the stomach.

For those receiving B12 shots as a treatment for a B12 deficiency, there are a few different forms, or vitamers, of synthesized vitamin B12 that can be used to handle the deficiency. These include:

  • Cyanocobalamin – This vitamer is used for food fortification, multi-vitamin products, and dietary supplements. Cyanocobalamin is suitable for these methods of treatment because of its stability during processing and storage.
  • Hydroxocobalamin – This vitamer is typically found within pharmacology. Due to its water solubility, it is commonly used for intramuscular or intravenous injections. Also used to reverse the effects of cyanide poisoning, this vitamer is the preferred course of treatment for those with intrinsic cobalamin metabolic disease and those with optic neuropathy as a symptom of pernicious anemia.
  • Adenosylcobalamin – This vitamer is an active cofactor form of vitamin B12. It naturally occurs in the liver and is active in the mitochondria.
  • Methylcobalamin – This vitamer is an active form of B12 that works with several enzymes to create amino acids, produce red blood cells, repair DNA, and assist with other essential physiological processes. This form of B12 is typically administered through injections and oral supplements.

Determining the right course of treatment for a vitamin B12 deficiency is between the patient and their healthcare provider. Above all, the most important thing is that the deficiency is properly treated, treatment is working well, and the quality of the patient’s life is improving.

Benefits of Vitamin B12 Shots

There are both vitamin B12 shot side effects and vitamin B12 shot benefits. Many of the benefits associated with the vitamin B12 shot include better mood, increased energy, alleviating anemia symptoms, weight loss, and many more. 

Though keep in mind that these benefits are realized when a vitamin B12 deficiency is reversed. As with any treatment, it is incredibly important to weigh both the risks and benefits associated with the course of treatment. To give you a better idea, listed below are the benefits associated with vitamin B12 shots:

  • Helping with red blood cell formation, which may boost energy and endurance
  • May support heart health by decreasing homocysteine levels
  • May help prevent cognitive decline
  • Anemia prevention (NIH, n.d.)
  • May reduce the risk age-related macular degeneration
  • May improve sperm count (Penn State, 2011)

While these are only some of the benefits associated with vitamin B12 shots, it is easy to see that vitamin B12 is responsible for so many functions within the body. 

Considering a deficiency can cause harm to many systems within the body, understanding the benefits of the B12 shot and knowing how it could improve the quality of your life is very important to leading a safe and healthy life. However, it is important to know the side-effects before you buy b12 shots.

foods high in vitamin B12

Side Effects of B12 Injections

Just as it is important to understand the benefits of the B12 shot, it is also incredibly important to know the B12 shot side effects. Before anyone makes a decision regarding their health, it is imperative that they know the risks and the benefits. 

Understanding both the B12 shot side effects, as well as the B12 shot side effects at the injection site, is important because it empowers you to make a decision regarding your treatment that is fully informed.

B12 shot side effects include, but are not limited to:

  • Swelling at the injection site
  • Mild diarrhea
  • Itching
  • Swelling in the body
  • Low potassium
  • Headache
  • Dizziness
  • Vomiting
  • Skin rash
  • Pulmonary edema and congestive heart failure (in early treatment)
  • Vein thrombosis
  • Polycythemia vera
  •  A very rare, but serious allergic reaction causing swelling of the face, tongue, and throat, and difficulty swallowing or breathing (anaphylaxis)
  • Restenosis
  • High blood pressure immediately after injection
  • Cold symptoms
  • Anxiety
  • Burning skin
  • Pink or red skin discoloration
  • Joint and muscle pain
  • Facial swelling
  • Numbness
  • Increase and blood volume and red blood cells

Let’s expand a bit on some of the more common B12 shot side effects:

Pain or Discomfort at Injection Site

This is the most common side effect of B12 shots simply because of the injection location. You may experience localized pain, swelling, and discomfort that should subside in a couple of days. If the pain does not go away you should report side effects to your healthcare professional.

Allergic Reactions

While it’s not necessarily a common issue, it’s an important one. Some people have allergic reactions to vitamin B12 injections. These reactions can include swelling, hives, difficulty breathing, and a rapid heart rate. If you experience these issues you should seek medical attention right away. 

A woman calming her anxiety

Dizziness or Lightheadedness

Some individuals may feel dizzy or lightheaded after receiving a vitamin B12 shot. This is usually transient and can be managed by lying down and resting.

It is crucial to consult with a healthcare professional before starting any vitamin B12 supplementation regimen or receiving vitamin B12 shots. They will assess your individual health needs, potential deficiencies, and the appropriateness of vitamin B12 injections for your specific situation.

For most people, oral vitamin B12 supplements or dietary changes can effectively address deficiencies without the need for injections. However, certain medical conditions, such as pernicious anemia or malabsorption disorders, may require ongoing B12 injections under medical supervision.

Considering the B12 shot side effects listed above, it is important to understand that some of these side effects are more common, while others are incredibly rare. This is another important discussion topic to bring up with your health care provider when evaluating your diagnosis and considering treatment.

In Conclusion

Any time we are faced with unfamiliar medical treatments, it is understandable to have questions and concerns. It makes sense to wonder if the benefits outweigh the B12 shot side effects. Considering how important vitamin B12 is to the optimal function of your body; it seems as though the answer would be, yes.

When you’re ready to talk to your doctor about your prescription for your vitamin B12 deficiency, you will want to ensure that you are sourcing your vitamin B12 supplement from the best place possible.

A great place to buy Vitamin B12 injections is through Invigor Medical. This trusted U.S. Pharmacy provides high-quality methylcobalamin to those deficient in vitamin B12 with a prescription for an injectable supplement.

Frequently Asked Questions

Are Vitamin B12 Shots More Effective Than Vitamin B12 Oral Supplements?

Both methods of treatment can deliver the desired results, and the majority of the “success” of treatment is determined on a case-by-case basis and what is most comfortable and effective for the individual patient. 

Some studies have shown that a high-dose, oral vitamin B12 was as effective as an intramuscular injection; however, other studies have determined that oral B12 supplements aren’t as fully absorbed during the digestive process. It’s best to talk with your doctor to determine which form of treatment is best for you.

Are Vitamin B12 Shots painful?

While this somewhat depends on the individual’s tolerance for pain, B12 injections are mostly considered relatively painless. Injections given into the muscle typically present some pain, swelling, and itching at the injection site. However, these symptoms are mild and wear off pretty quickly.

What are the side effects of B12 injections?

Side effects of B12 injections may include mild discomfort at the injection site, redness, or swelling. Some individuals may experience rare allergic reactions or an upset stomach.

Why do I feel weird after a B12 shot?

Feeling “weird” after a B12 shot can vary from person to person. Some may feel a temporary sensation due to the injection itself, while others might experience mild dizziness, nausea, or a feeling of energy. If you have concerns about how you feel after a B12 shot, it’s best to discuss them with your healthcare provider for personalized guidance.

While we strive to always provide accurate, current, and safe advice in all of our articles and guides, it’s important to stress that they are no substitute for medical advice from a doctor or healthcare provider. You should always consult a practicing professional who can diagnose your specific case. The content we’ve included in this guide is merely meant to be informational and does not constitute medical advice.


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