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Hydroxocobalamin Side Effects

Not all side effects for hydroxocobalamin may be reported. You should always consult a doctor or healthcare professional for medical advice. Side effects can be reported to the FDA here.

For the Consumer

Applies to hydroxocobalamin: kit

Check with your doctor if any of these most COMMON side effects persist or become bothersome:

Acne-like rash; headache; nausea; red-colored urine; skin redness.

Seek medical attention right away if any of these SEVERE side effects occur while taking hydroxocobalamin:

Severe allergic reactions (rash; hives; itching; difficulty breathing; tightness in the chest; swelling of the mouth, face, lips, or tongue; unusual hoarseness); bloody stools; chest discomfort; dizziness; dryness or tightness of the throat; eye irritation, redness, or swelling; fast or irregular heartbeat; flushing; memory problems; pain or redness at the injection site; restlessness; severe or persistent diarrhea, nausea, vomiting, or stomach pain; severe or persistent headache; shortness of breath; swelling of the ankles or feet; trouble swallowing.

For Healthcare Professionals

Applies to hydroxocobalamin: compounding powder, injectable solution, intravenous powder for injection


Gastrointestinal side effects have included mild transient diarrhea and nausea.[Ref]


Other side effects have included itching and feeling of swelling of the entire body.[Ref]


Dermatologic side effects have included transitory exanthema and erythema.[Ref]


Hypersensitivity side effects have rarely included anaphylactic reactions.[Ref]


Local side effects have included infusion site reaction and pain with injection.[Ref]


Renal side effects have included chromaturia.


Cardiovascular side effects, following intravenous administration, have included increased blood pressure.[Ref]


1. "Product Information. Hydro-Cobex (hydroxocobalamin)." Major Pharmaceuticals Inc, Rosemont, IL.

2. "Product Information. Cyanokit (hydroxocobalamin)." Meridian Medical Technologies Inc, Columbia, MD.

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