Cyanocobalamin injection is used to treat and prevent a lack of vitamin B₁₂ that may be caused by any of the following: pernicious anemia (lack of a natural substance needed to absorb vitamin B₁₂ from the intestine); certain diseases, infections, or medications that decrease the amount of vitamin B₁₂ absorbed from food; or a vegan diet (strict vegetarian diet that does not allow any animal products, including dairy products and eggs). Lack of vitamin B₁₂ may cause anemia (condition in which the red blood cells do not bring enough oxygen to the organs) and permanent damage to the nerves. Cyanocobalamin injection also may be given as a test to see how well the body can absorb vitamin B₁₂. Cyanocobalamin injection is in a class of medications called vitamins. Because it is injected straight into the bloodstream, it can be used to supply vitamin B₁₂ to people who cannot absorb this vitamin through the intestine.

Cyanocobalamin comes as a solution (liquid) to be injected into a muscle or just under the skin. It is usually injected by a healthcare provider in an office or clinic. You will probably receive cyanocobalamin injection once a day for the first 6-7 days of your treatment. As your red blood cells return to normal, you will probably receive the medication every other day for 2 weeks, and then every 3-4 days for 2-3 weeks. After your anemia has been treated, you will probably receive the medication once a month to prevent your symptoms from coming back.

Cyanocobalamin injection will supply you with enough vitamin B₁₂ only as long as you receive injections regularly. You may receive cyanocobalamin injections every month for the rest of your life. Keep all appointments to receive cyanocobalamin injections even if you feel well. If you stop receiving cyanocobalamin injections, your anemia may return and your nerves may be damaged.

Before using cyanocobalamin injection,

• tell your doctor and pharmacist if you are allergic to cyanocobalamin injection, nasal gel, or tablets; hydroxocobalamin; multi-vitamins; any other medications or vitamins; or cobalt.
• tell your doctor and pharmacist what prescription and nonprescription medications, vitamins, nutritional supplements, and herbal products you are taking. Be sure to mention any of the following: antibiotics such as chloramphenicol; colchicine; folic acid; methotrexate (Rheumatrex, Trexall); para-aminosalicylic acid (Paser); and pyrimethamine (Daraprim). Your doctor may need to change the doses of your medications or monitor you carefully for side effects.
• tell your doctor if you drink or have ever drunk large amounts of alcohol and if you have or have ever had Leber's hereditary optic neuropathy (slow, painless loss of vision, first in one eye and then in the other) or kidney disease.
• tell your doctor if you are pregnant, plan to become pregnant, or are breast-feeding. If you become pregnant while using cyanocobalamin injection, call your doctor. Talk to your doctor about the amount of vitamin B₁₂ you should get every day when you are pregnant or breast-feeding.

If you miss an appointment to receive a cyanocobalamin injection, call your doctor as soon as possible.

In case of overdose, call the poison control helpline at 1-800-222-1222. Information is also available online at https://www.poisonhelp.org/help. If the victim has collapsed, had a seizure, has trouble breathing, or can't be awakened, immediately call emergency services at 911.

Your doctor will store this medication in his or her office.

Unless your doctor tells you otherwise, continue your normal diet.

Cyanocobalamin injection may cause side effects. Tell your doctor if either of these symptoms is severe or does not go away:

• diarrhea
• feeling as if your entire body as swollen

Some side effects can be serious. The following symptoms are uncommon, but if you experience any of them, call your doctor immediately:

• muscle weakness, cramps, or pain
• leg pain
• extreme thirst
• frequent urination
• confusion
• shortness of breath, especially when you exercise or lie down
• coughing or wheezing
• fast heartbeat
• extreme tiredness
• swelling of the arms, hands, feet, ankles or lower legs
• pain, warmth, redness, swelling or tenderness in one leg
• headache
• dizziness
• red skin color, especially on the face
• hives
• rash
• itching
• difficulty breathing or swallowing

Cyanocobalamin injection may cause other side effects. Call your doctor if you have any unusual problems while taking this medication.

If you experience a serious side effect, you or your doctor may send a report to the Food and Drug Administration's (FDA) MedWatch Adverse Event Reporting program online (http://www.fda.gov/Safety/MedWatch) or by phone (1-800-332-1088).

Cyanocobalamin injection is also sometimes used to treat inherited conditions that decrease the absorption of vitamin B₁₂ from the intestine. Cyanocobalamin injection is also sometimes used to treat methylmalonic aciduria (an inherited disease in which the body cannot break down protein) and is sometimes given to unborn babies to prevent methylmalonic aciduria after birth. Talk to your doctor about the possible risks of using this drug for your condition.

This medication may be prescribed for other uses; ask your doctor or pharmacist for more information.

Keep all appointments with your doctor and the laboratory. Your doctor will order certain lab tests to check your body's response to cyanocobalamin injection.

It is important for you to keep a written list of all of the prescription and nonprescription (over-the-counter) medicines you are taking, as well as any products such as vitamins, minerals, or other dietary supplements. You should bring this list with you each time you visit a doctor or if you are admitted to a hospital. It is also important information to carry with you in case of emergencies.

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