A gloved hand holding a syringe filled with red vitamin B12 solution, representing nutrient injection therapy for energy and wellness support.

What Are Vitamin B12 Shots?

Vitamin B12 is a nutrient your body needs to function at its best. It helps your body produce energy, keep nerve cells healthy, and contributes to red blood cell production. If your body is not operating at its full potential due to low levels of this vitamin, B12 shots are an effective, high-impact way to get a direct dose of cobalamin (active B12) into your system, straight into the muscle.

Eating animal products typically gives your body more than enough of the nutrient, but there are particular groups of people more susceptible to a B12 deficiency. B12 shots can be especially helpful if you are older, do not eat animal products, have conditions that impact nutrient absorption, or take medications that interfere with nutrient absorption.

Vitamin B12 Benefits

If you have a deficiency, B12 supplementation can:

  • Enhance alertness and cognitive function

  • Encourage the synthesis of healthy red blood cells

  • Aid in controlling sleep cycles

  • Bolster the immune system

  • Aid in weight management and boost metabolism.

  • Reduce tingling and numbness by improving nerve health and function.

One of the primary benefits of B12 shots is the bioavailability of the vitamin. When active B12 is injected into your muscle, it bypasses the digestive tract, allowing your body to absorb 100% of the nutrient.

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Contraindications

  • Allergy to cobalt or vitamin B12. Since B12 contains cobalt, people with known sensitivities should not receive injections.

  • Leber’s disease (hereditary optic nerve atrophy)

  • Polycythemia vera

  • Low potassium levels (hypokalemia)

  • History of blood clots

Preparation Details

  • Avoid alcohol when receiving B12 shots.

B12 Shots FAQ

What does vitamin B12 do?

B12 supports a number of bodily functions that contribute to cognitive wellness, energy metabolism, and healthy blood cells.

Vitamin B12 is responsible for:

  • Supporting myelin, the protective covering that surrounds your nerves, so you can think clearly, recall information, and maintain a stable mood.

  • Converting the food you eat into energy that your body can use.

  • Making healthy red blood cells.

  • Helping your cells produce new DNA, which is necessary for cell division, tissue growth, and repair.

Who is at risk for Vitamin B12 deficiency?

You may not get enough B12 in your diet if you are:

  • Vegan

  • Vegetarian

  • Over 50

  • Living with digestive conditions that affect nutrient absorption, such as IBS, celiac, or Crohn’s disease

  • Taking certain medications like metformin or proton pump inhibitors (PPIs)

What are the symptoms of B12 deficiency?

Low B12 levels are associated with symptoms like:

  • Fatigue or low energy

  • Difficulty concentrating

  • Numbness or tingling in hands and feet

  • Swollen, inflamed tongue

  • Dizziness or unsteadiness

  • Muscle weakness

  • Vision problems like blurriness or double vision

What are the possible B12 injection side effects?

B12 injections are a safe, fast, and effective method to raise vitamin B12 levels in the body, especially for people with absorption problems. The most common side effects of B12 shots are minor and typically localized to the injection site. These include pain, swelling, itching, bruising, and redness. A small number of people are allergic to B12, but this is rare.

How long do B12 injections take to work?

Depending on your body and the severity of your deficiency, B12 injections can start to work in a matter of hours to a few days.

Some people, particularly those who were severely deficient, report a sudden improvement in energy, focus, or mood within 24 to 72 hours.

For others, it might take a few weeks of consistent injections before you notice a change if your symptoms are more complicated, such as numbness, exhaustion, or memory problems.

If your B12 levels were consistently low, it may take several months to restore your body’s levels.

B12 Shots Aftercare

  • Watch for rare side effects like dizziness, rash, or itching. Please report these side effects immediately to your provider—especially if it is your first time receiving B12 injections.  

  • Stay hydrated since drinking water can help your body process and disperse the vitamin efficiently.

  • Light movement helps disperse the injection and may prevent soreness.