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Nascobal Side Effects

Generic name: cyanocobalamin

Medically reviewed by Last updated on Apr 1, 2024.

Note: This document contains side effect information about cyanocobalamin. Some dosage forms listed on this page may not apply to the brand name Nascobal.

Applies to cyanocobalamin: intramuscular solution. Other dosage forms:

Serious side effects of Nascobal

Along with its needed effects, cyanocobalamin (the active ingredient contained in Nascobal) may cause some unwanted effects. Although not all of these side effects may occur, if they do occur they may need medical attention.

Check with your doctor or nurse immediately if any of the following side effects occur while taking cyanocobalamin:

Incidence not known

Other side effects of Nascobal

Some side effects of cyanocobalamin may occur that usually do not need medical attention. These side effects may go away during treatment as your body adjusts to the medicine. Also, your health care professional may be able to tell you about ways to prevent or reduce some of these side effects.

Check with your health care professional if any of the following side effects continue or are bothersome or if you have any questions about them:

Incidence not known

For Healthcare Professionals

Applies to cyanocobalamin: compounding powder, injectable solution, intramuscular solution, nasal gel, nasal spray, oral liquid, oral tablet, oral tablet chewable, oral tablet disintegrating, oral tablet extended release, sublingual liquid, sublingual lozenge, sublingual tablet.


Frequency not reported: Congestive heart failure, peripheral vascular thrombosis, cardiac arrest, low blood pressure[Ref]


Frequency not reported: Anaphylactic shock and death, allergic hypersensitivity reactions[Ref]

Patients sensitized to the injectable product are often able to tolerate the oral route without problems.[Ref]


Frequency not reported: Mild transient diarrhea, prolonged abdominal pain, prolonged nausea or vomiting[Ref]

Nervous system

Frequency not reported: Severe dizziness, drowsiness, muscular paralysis, loss of consciousness[Ref]


Frequency not reported: Itching, transitory exanthema, acneiform eruptions, bullous eruptions[Ref]


Frequency not reported: Pulmonary edema[Ref]


Frequency not reported: Hypokalemia[Ref]


Frequency not reported: Polycythemia vera[Ref]


Frequency not reported: Vision problems[Ref]


Frequency not reported: Feeling of swelling of entire body[Ref]


1. Cerner Multum, Inc. "Australian Product Information."

2. (2017) "Product Information. Cyanocobalamin (cyanocobalamin)." West Ward Pharmaceutical Corporation

3. Cerner Multum, Inc. "UK Summary of Product Characteristics."

Further information

Always consult your healthcare provider to ensure the information displayed on this page applies to your personal circumstances.

Some side effects may not be reported. You may report them to the FDA.