What You Should Know Before Taking B12 Injections

Vitamin B12 has very low toxicity even when taken in large doses, however as with all medications and supplements there are some risks associated with its use.

B12 warnings may range from mild side effects such as upset stomach to serious reactions such as heart failure.

Many B12 warnings are related to side effects from allergic reactions or interactions with other medications.

However, people with certain diseases such as Leber’s disease can also experience adverse reactions, causing rapid progress of the disease when receiving B12 treatment.

Patients may also experience side effects related to B12 injections at the site of the injection.

These symptoms are typically mild and include pain and redness or itching at the injection site.

Though serious side effects rarely occur, it is important to be aware of the potential risks and B12 warnings.

While direct allergies to vitamins are extremely rare, people who are allergic to cobalt (a key compound in cobalamin) should not take vitamin B12 injections or supplements.

Patient’s who are allergic to cobalt or have other allergies should inform their doctor and in some cases the doctor may recommend starting with smaller test dosages.  

In addition to cobalt, B12 injections or supplements may contain inactive ingredients such as benzyl alcohol that can produce allergic reactions.

Some allergic reactions associated with B12 supplementation may include difficulty breathing, chest pains or swelling of the face or tongue.

In addition to allergic reaction, some B12 warnings include side effects from ingredients such as aluminum.  

Aluminum may be found in vitamin B12 injections and over time can cause dangerous levels to build up in the body.

This occurrence is infrequent but the risk may be increased with extended use, especially in patients with kidney disease.

Some of the symptoms associated with too much aluminum are noticeable mental changes, muscle weakness and bone pain.

Perhaps the largest list of B12 warnings is in the drug interaction category so persons taking B12 should always inform their doctor of any medications or supplements they are taking.

In addition to adverse reactions and associated side effects, B12 may be ineffective when taken with other medications.

READ : Which Vegan Foods Contain the Most Vitamin B12?

Furthermore, taking B12 injections or supplements may also impact the effectiveness of medications or mask problems associated with health problems other than B12 deficiency.

The following list of B12 warnings is sampling of reported side effects but should not be considered complete.

Always consult your health professional for medical advise before starting a B12 regimen.

B12 Warnings – Side Effects

•Side effects may include pain or redness at the site of injection

•Mild Diarrhea


• The feeling of swelling over the entire body

• May cause low potassium levels (muscle cramps, weakness, irregular heartbeat)

• B12 injections containing aluminum may cause too much aluminum to build up in the body (mental changes, muscle weakness, bone pain)

• Inflammatory acne

B12 Warnings – Allergic Reaction

• Persons who are allergic to Cobalt should not take B12 supplements

• Benzyl Alcohol is a preservative that is used some B12 injections and has been

• Symptoms may include chest pain, difficulty breathing and swelling of face and tongue

B12 Warnings – Drug Interactions

Vitamin B12 injections and or supplements have reported adverse interaction with but not limited to:

• Medications that affect blood cell production such as chloramphenicol , Anti-Cancer and HIV drugs.

• Anti-infection drugs such as:  amoxicillin, erythromycin, pyrimethamine, methotrexate

B12 Warnings – Disease Adverse Reactions

• Lebers Disease is a hereditary optic nerve disease that progress rapidly with the use of Cyanocobalamin forms of B12.

• B12 treatment can obscure folate deficiency in megaloblastic anemia

• B12 supplementation may unmask and exacerbate a condition known as polycythemia vera, where the number of blood cells are too high.

If you experience any of these B12 warnings, consult your doctor before continuing use of B12 supplements.

Similar Posts

Leave a Reply

Your email address will not be published. Required fields are marked *