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

Last Updated: August 29, 2025
A doctor holding a white card with the words SIDE EFFECTS in bold red letters. The doctors face is blurred, and a stethoscope is visible around their neck.
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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.

Written by

Derek Berkey
Derek Berkey
CEO, Invigor Medical | Science-Based Wellness Expert
Derek Berkey is the Chief Executive Officer of Invigor Medical, a telehealth company specializing in weight management, sexual health, and healthy aging. He serves as an author and reviewer, ensuring all content is grounded in science-based, patient‑centered insight.

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Derek Berkey
Derek Berkey
CEO, Invigor Medical | Science-Based Wellness Expert
Derek Berkey is the Chief Executive Officer of Invigor Medical, a telehealth company specializing in weight management, sexual health, and healthy aging. He serves as an author and reviewer, ensuring all content is grounded in science-based, patient‑centered insight.

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