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Cyanocobalamin Side Effects Center
Medical Editor: John P. Cunha, DO, FACOEP
Cyanocobalamin (vitamin B12) is a man-made form of vitamin B12 used to treat low levels (deficiency) of Vitamin B12. A B12 deficiency may occur in certain health conditions (e.g., poor nutrition, stomach/intestinal problems, infection, cancer) and may result in anemia, stomach problems, and nerve damage. Cyanocobalamin is available in generic form. Common side effects of Cyanocobalamin include injection site reactions (pain, redness, swelling, irritation), diarrhea, nausea, upset stomach, itching, rash, headache, dizziness, weakness, numbness or tingling, fever, joint pain, or a feeling of swelling all over the body.
To treat pernicious anemia a dose of 100 mcg daily of Cyanocobalamin for 6 or 7 days should be administered by intramuscular or deep subcutaneous injection. Cyanocobalamin may interact with drugs that may affect blood cell production (e.g., chloramphenicol, anti-cancer drugs, HIV drugs), or supplements such as folic acid. Tell your doctor all medications and supplements you use. During pregnancy, Cyanocobalamin should be used only when prescribed. This medication may pass into breast milk. Consult your doctor before breastfeeding.
Our Cyanocobalamin (vitamin B12) Side Effects Drug Center provides a comprehensive view of available drug information on the potential side effects when taking this medication.
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.
What is Patient Information in Detail?
Easy-to-read and understand detailed drug information and pill images for the patient or caregiver from Cerner Multum.
Cyanocobalamin in Detail - Patient Information: 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 a serious side effect such as:
- chest pain;
- feeling short of breath, even with mild exertion;
- swelling, rapid weight gain; or
- unusual warmth, redness, or pain in an arm or leg.
Less serious side effects may include:
- headache, dizziness, weakness;
- nausea, upset stomach, diarrhea;
- numbness or tingling;
- pain, swelling, redness, or irritation where the injection was given;
- joint pain; or
- itching or rash.
This is not a complete list of side effects and others may occur. Tell your doctor about any unusual or bothersome side effect. You may report side effects to FDA at 1-800-FDA-1088.
Read the entire detailed patient monograph for Cyanocobalamin (Cyanocobalamin)
What is Patient Information Overview?
A concise overview of the drug for the patient or caregiver from First DataBank.
Cyanocobalamin Overview - Patient Information: Side Effects
Remember that your doctor has prescribed this medication because he or she has judged that the benefit to you is greater than the risk of side effects. Many people using this medication do not have serious side effects.
This medication may cause low potassium levels in the blood (hypokalemia). Tell your doctor immediately if any of these unlikely but serious side effects occur: muscle cramps, weakness, irregular heartbeat.
People who have a rare blood disorder (polycythemia vera) may infrequently have symptoms related to this disorder while taking cyanocobalamin. Seek immediate medical attention if any of these rare but very serious symptoms occur: chest pain (especially with shortness of breath), weakness on one side of the body, sudden vision changes, slurred speech.
Get medical help right away if you have any very serious side effects, including: swelling ankles/feet, trouble breathing, unusual tiredness.
A very serious allergic reaction to this drug is rare. However, seek immediate medical attention if you notice any symptoms of a serious allergic reaction, including: rash, itching/swelling (especially of the face/tongue/throat), severe dizziness, trouble breathing.
This is not a complete list of possible side effects. If you notice other effects not listed above, contact your doctor or pharmacist.
In the US -
Call your doctor for medical advice about side effects. You may report side effects to FDA at 1-800-FDA-1088.
In Canada - Call your doctor for medical advice about side effects. You may report side effects to Health Canada at 1-866-234-2345.
Read the entire patient information overview for Cyanocobalamin (Cyanocobalamin)
What is Prescribing information?
The FDA package insert formatted in easy-to-find categories for health professionals and clinicians.
Cyanocobalamin FDA Prescribing Information: Side Effects
Hematological: Polycythemia vera
Gastrointestinal: Mild transient diarrhea
Dermatological: Itching; transitory exanthema
Miscellaneous: Feeling of swelling of entire body
Read the entire FDA prescribing information for Cyanocobalamin (Cyanocobalamin)
Additional Cyanocobalamin Information
Cyanocobalamin - User Reviews
Cyanocobalamin User Reviews
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Report Problems to the Food and Drug Administration
You are encouraged to report negative side effects of prescription drugs to the FDA. Visit the FDA MedWatch website or call 1-800-FDA-1088.
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