Does the Vitamin B12 Shot Have Side Effects?

Vitamin B12 is to the human body what gasoline is to a car; without these two components, neither vehicle will go. Just as a car needs gasoline, the human body needs regular doses of B12. A diet that includes meat, fish, and dairy products provides natural dietary sources; however, these foods typically carry a heavy toxic load. Vegetarians and especially vegans can suffer from B12 deficiency, yet meat eaters also fall victim. Regardless of the cause, B12 deficiency may require a high level of supplementation, often in the form of a B12 injection.

What is a Vitamin B12 Shot?

The shot delivers a high dose of therapeutic B12, usually in the form of cyanocobalamin or hydroxocobalamin. Although oral supplementation with vegan-friendly products is available for those who can digest B12, the amount absorbed may not be enough to prevent deficiency for some people. Recent research suggests oral supplementation with the two active forms of B12, methylcobalamin and adenosylcobalamin, may be as effective as a B12 shot. [1]

Those who cannot digest or absorb B12 as a result of inherited genetics or damage to the stomach and small intestine require more than can be absorbed from sublingual supplementation. In situations where a high dose is needed, or where injection is the only option, the B12 shot is used. In some cases, B12 shots are used as an energy booster, since B12 plays a critical role in cellular energy production.

Reasons for a B12 Shot

Vitamin B12 deficiency symptoms include depression and mood disorders, fatigue, memory failure, anemia, low blood pressure, and high homocysteine levels. While the shot addresses B12 deficiency, it may also be prescribed to boost energy, as a therapy for depression, or to drive cognitive function. Researchers are also exploring its potential as a therapy for bipolar disorders, shaky leg syndrome, and autism.

Getting the B12 Shot

Before getting the shot, make sure to inform your doctor of any allergies, nutritional supplements you may be taking, or if you've recently consumed large amounts of alcohol. At the appointment, the doctor or healthcare professional delivers the shot directly into muscle, usually into the thigh or upper arm, for easy absorption into the bloodstream.

B12 Shot Side Effects

The dosage amount and the type of B12 used appears to have some control over side effects. As a note, the common side effects of excess vitamin intake include flushing, diarrhea, nausea, and vomiting. Here are the side effects you might experience from the two common B12 shots:


This form of B12 is the one we find in our food. When delivered as a B12 shot, mild side effects may include soreness at the injection site, itching, diarrhea, and swelling. Serious side effects include muscle cramping, weakness, or an irregular heartbeat. Although rare, some very serious side effects are chest pain, shortness of breath, slurred speech, sudden vision changes, and weakness on one side of the body. You should always contact your doctor immediately if you experience any of …read more

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