Medically reviewed on February 27, 2018
What is Vitamin B-12 ?
Vitamin B-12 is a man-made form of vitamin B12. Vitamin B12 is important for growth, cell reproduction, blood formation, and protein and tissue synthesis.
Vitamin B-12 may also be used for purposes not listed in this medication guide.
You should not use Vitamin B-12 if you are allergic to cobalt, or if you have Leber's disease.
Before taking this medicine
You should not use this medicine if you are allergic to Vitamin B-12 or cobalt, or if you have Leber's disease (an inherited form of vision loss). This medicine can lead to optic nerve damage (and possibly blindness) in people with Leber's disease.
To make sure Vitamin B-12 is safe for you, tell your doctor if you have:
cold or allergy symptoms that affect your nose (sinus congestion, sneezing);
kidney or liver disease;
iron or folic acid deficiency;
any type of infection; or
if you are receiving any medication or treatment that affects bone marrow.
FDA pregnancy category C. It is not known whether Vitamin B-12 will harm an unborn baby. Tell your doctor if you are pregnant or plan to become pregnant while using this medicine.
Cyanocobalamin can pass into breast milk and may harm a nursing baby. Tell your doctor if you are breast-feeding a baby.
How is Vitamin B-12 given?
Follow all directions on your prescription label. Do not use Vitamin B-12 in larger or smaller amounts or for longer than recommended.
Vitamin B-12 is injected into a muscle or under the skin. You may be shown how to use injections at home. Do not self-inject this medicine if you do not understand how to give the injection and properly dispose of used needles and syringes.
Use a disposable needle only once. Follow any state or local laws about throwing away used needles and syringes. Use a puncture-proof "sharps" disposal container (ask your pharmacist where to get one and how to throw it away). Keep this container out of the reach of children and pets.
Your dose needs may change if you become pregnant, if you breast-feed, or if you eat a vegetarian diet. Tell your doctor about any changes in your diet or medical condition.
While using Vitamin B-12, you may need frequent blood tests.
Use Vitamin B-12 regularly to get the most benefit. Get your prescription refilled before you run out of medicine completely.
Pernicious anemia is also treated with folic acid to help maintain red blood cells. However, folic acid will not treat Vitamin B12 deficiency and will not prevent possible damage to the spinal cord. Use all of your medications as directed.
To treat pernicious anemia, you may have to use Vitamin B-12 for the rest of your life. Do not stop using the medicine unless your doctor tells you to. Untreated vitamin B12 deficiency can lead to a recurrence of anemia and irreversible nerve damage.
Store this medication at room temperature away from moisture, heat, and light.
What happens if I miss a dose?
Call your doctor for instructions if you miss a dose.
What happens if I overdose?
Seek emergency medical attention or call the Poison Help line at 1-800-222-1222.
What should I avoid while using Vitamin B-12?
Avoid drinking large amounts of alcohol while you are being treated with Vitamin B-12.
Vitamin B-12 side effects
Get emergency medical help if you have any of these signs of an allergic reaction: hives; difficulty breathing; swelling of your face, lips, tongue, or throat.
Call your doctor at once if you have:
numbness or tingling in your hands or feet;
signs of fluid build-up around your lungs--anxiety, sweating, pale skin, severe shortness of breath, wheezing, gasping for breath, cough with foamy mucus, chest pain; or
signs of low potassium--confusion, uneven heart rate, extreme thirst, increased urination, leg discomfort, muscle weakness or limp feeling.
Common side effects may include:
swelling, rapid weight gain;
itching or mild rash.
This is not a complete list of side effects and others may occur. Call your doctor for medical advice about side effects. You may report side effects to FDA at 1-800-FDA-1088.
See also: Side effects (in more detail)
What other drugs will affect Vitamin B-12?
Other drugs may interact with cyanocobalamin, including prescription and over-the-counter medicines, vitamins, and herbal products. Tell each of your health care providers about all medicines you use now and any medicine you start or stop using.
Remember, keep this and all other medicines out of the reach of children, never share your medicines with others, and use this medication only for the indication prescribed.
Always consult your healthcare provider to ensure the information displayed on this page applies to your personal circumstances.
Copyright 1996-2018 Cerner Multum, Inc. Version: 2.01.
More about Vitamin B12 (cyanocobalamin)
- Vitamin B12 Side Effects
- During Pregnancy
- Dosage Information
- Drug Interactions
- Compare Alternatives
- Support Group
- 11 Reviews
- Drug class: vitamins