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.
Hydroxocobalamin is usually given in an emergency, so you may not have time to tell your caregivers about any drugs you take or medical conditions you have. However, you will need follow-up medical care after receiving this medication. Tell your doctor if you have high blood pressure, heart disease, or congestive heart failure.
You may develop an acne-like skin rash from 1 week to as late as 4 weeks after you are treated with hydroxocobalamin. This rash should go away without treatment. Call your doctor if you have a rash that does not clear up on its own.
This medication can cause you to have unusual results with certain medical tests. Tell any doctor who treats you that you have recently received a hydroxocobalamin injection.