Are B12 injections harmful?
Christopher Davis
Updated on May 30, 2026
Vitamin B12 injections are generally considered to be very safe. They have no major side effects. However, in very rare cases, some people can experience side effects caused by allergic reactions or sensitivity ( 29 , 30 ).
What are the side effects of having B12 injections?
Vitamin B-12 side effectsGet emergency medical help if you have signs of an allergic reaction: hives; difficulty breathing; swelling of your face, lips, tongue, or throat. Vitamin B-12 may cause serious side effects.
Are B12 injections healthy?
People who are deficient in vitamin B12 are often prescribed B12 shots. This method is a very effective way of reversing or preventing a deficiency because it allows for 100% absorption directly into the tissues. These days, vitamin B12 shots have even become popular in people without the vitamin deficiency.Are there negative side effects to B12?
High doses of vitamin B-12, such as those used to treat a deficiency, might cause: Headache. Nausea and vomiting. Diarrhea.Can B12 injections cause heart problems?
B12 injections may contribute to low potassium levels in your body. Though rare, this reaction can cause muscle cramping, extreme fatigue, and an irregular heartbeat.Are Vitamin B12 Injections Worth Your Money?
What medications should not be taken with B12?
Certain medications can decrease the absorption of vitamin B12, including: colchicine, metformin, extended-release potassium products, antibiotics (such as gentamicin, neomycin, tobramycin), anti-seizure medications (such as phenobarbital, phenytoin, primidone), medications to treat heartburn (such as H2 blockers ...Is the NHS stopping B12 injections?
Nationally, all NHS organisations will be stopping B12 injections. Some will offer oral on a script, other areas have stopped and asked patients to purchase it.What are the symptoms of low B12?
Symptoms of vitamin B12 deficiency
- a pale yellow tinge to your skin.
- a sore and red tongue (glossitis)
- mouth ulcers.
- pins and needles (paraesthesia)
- changes in the way that you walk and move around.
- disturbed vision.
- irritability.
- depression.