Cyanocobalamin (Intramuscular)

As a man-made version of vitamin B12, Cyanocobalamin is used to treat and prevent low blood levels of the compound in patients who have undergone certain surgical procedures.


Cyanocobalamin is a synthetic version of vitamin B12, which is converted by the human body into an active B12 compound. It is typically prescribed in patients who have recently undergone a surgical procedure to remove part or all of the stomach or intestine, in order to ensure there are adequate serum levels of B12 in the body. Having some or all of their small intestine by-passed can make it difficult for the body to acquire B12 via vitamin supplements or food.

This medicine can also be used to treat patients who are suffering from vitamin B12 deficiency (due to low intake of the compound from food), pernicious anemia, or as part of a combined treatment for malignancy, liver disease, kidney disease, haemorrhage and/or thyrotoxicosis. It can also be used to perform the Schilling test, which is an examination designed to check the body's ability to absorb vitamin B12.

Poor absorption of vitamin B12 may also be related to coeliac disease. Before prescribing injections of Cyanocobalamin, a doctor should test for this condition.

Type of medicine

  • Vitamin

Conditions treated

  • Vitamin B12 deficiency
  • Pernicious anemia

Side effects

As with many medicines, Cyanocobalamin can cause unwanted side effects along with its desired effects. The most commonly reported side effects experienced by patients undergoing a course of treatment with this medicine include stomach pain, bleeding from the gums or nose, blue lips and fingernails, coughing, chest pain, decreased urination, difficulty swallowing, dizziness, dilated neck veins, extreme fatigue, fast heartbeat, headache, increased sweating, irregular heartbeat, pale skin, ringing in the ears, tightness in the chest, weight gain, diarrhea, skin rash and/or unusual tiredness or weakness.

As the patient continues to undergo treatment with Cyanocobalamin as prescribed, many (if not all) of the previously mentioned side effects should lessen. If they get worse or persist over time, the patient is advised to follow this up with their healthcare provider immediately. In some instances, a doctor may be able to recommend ways of alleviating uncomfortable side effects via natural or over the counter remedies and products.

Most patients will typically only experience minimal side effects while undergoing treatment with Cyanocobalamin. Most doctors agree that the benefits of treating vitamin B12 deficiency, which is a potentially serious condition, far outweigh the risks of experiencing minor side effects.

Because Cyanocobalamin has the propensity to cause dizziness and extreme fatigue, patients are advised to avoid driving or operating heavy machinery until it has been observed that they are safe to do so and not experiencing side effects which could affect motor skills or vision.


As with all drugs, it is imperative that patients only take Cyanocobalamin as directed by a doctor. This means that patients should avoid administering more of the vitamin than advised, either in terms of frequency or dose size. In addition to this, patients should stop taking this medicine if advised to do so by their doctor, even if they still have a supply of it remaining.

Although the manufacturers of Cyanocobalamin provide generalized dosage instructions, it should be reiterated that such recommendations can be altered at the discretion of the patient's doctor. A doctor will take into account a number of factors when determining a suitable dose, such as the weight, height, age, and condition of the patient, among any other factors pertinent to use of this medication.

Adult dosage for vitamin B12 deficiency:

Adults should be administered between 25 and 2000mcg daily to combat B12 deficiency. A doctor will be able to determine the precise dosage after conducting blood tests. Depending on the patient response, a doctor may decide to switch B12 intake from intramuscular to oral administration, unless there is a reason not to do so.

Adult dosage for pernicious anemia:

Adults with pernicious anemia should receive 1000mcg intramuscularly once per day for 6 to 7 days. If the patient responds positively to this treatment, then the following doses may be applied from thereon in:

  • style="font-weight: 400;">100mcg every second day, for a fortnight, followed by:
  • 100mcg every 3 to 4 days for a fortnight to 3 weeks, followed by:
  • A maintenance dose of 100 to 1000mcg, administered monthly.

Patients with this condition will require regular B12 administration for the rest of their lives. Failure to continue treatment with Cyanocobalamin will cause anemia to return, which can result in irreversible and incapacitating damage to the spinal cord and nerves. Taking folic acid can prevent anemia, but will not protect against degeneration of the spinal cord.

Schilling test:

In order to perform the Schilling test, which determines how well the body absorbs vitamin B12, 1000mcg should be administered intramuscularly.

Pediatric dosage for vitamin B12 deficiency:

Children with B12 deficiency should receive between 0.5mcg and 3mcg daily, with regular monitoring to track patient response to the condition.

Patients are warned against taking excessive doses of Cyanocobalamin. If a patient experiences signs of an overdose (difficulty breathing, slow or fast heartbeat, unconsciousness, seizures or loss of coordination) they are advised to contact their local poison control center on 1800-222-1222 or the emergency services on 911.


All drugs have the potential to interact with other chemicals or medicines in the human body. This can cause one or more medicines to become ineffective, or can even cause dangerous or potentially fatal reactions in the patient. Because of these possibilities, patients are advised to keep a fully detailed list of all drugs they are currently taking. This extends to herbal supplements, complementary medicines and over the counter remedies as well as prescription medications.

Below is a list of drugs known to interact majorly with Cyanocobalamin. Patients who are already taking any of these medicines should inform their doctor prior to undergoing treatment with Cyanocobalamin:

  • Arsenic trioxide
  • Aspirin
  • Aminosalicylic acid
  • Amoxicillin
  • Bisacodyl
  • Sodium bicarbonate
  • Calcium carbonate
  • Cimetidine
  • Chloramphenicol
  • Dexlansoprazole
  • Esomeprazole
  • Famotidine
  • Lansoprazole
  • Lidocaine
  • Nizatidine
  • Omeprazole
  • Pantoprazole
  • Potassium bicarbonate
  • Potassium chloride
  • Rabeprazole
  • Ranitidine bismuth citrate


Patients who have Leber's disease should not undergo treatment with Cyanocobalamin. This is because this medicine can cause optic nerve damage (and potentially blindness) in patients with Leber's disease. Patients who are allergic to cobalt should also avoid treatment with this medication.

Cyanocobalamin can cause complications if used on patients with certain other medical conditions. Before taking this medicine, patients should inform their doctor if they have any of the following:

  • Iron deficiency
  • Folic acid deficiency
  • Kidney disease
  • Liver disease
  • Bone marrow issues which require treatment
  • Any kind of infection

In some patients, hypokalemia resulting in death has occurred during Cyanocobalamin therapy due to increased red blood cell requirements during hematopoiesis. To avoid this, clinical monitoring and correction of potassium levels before and during therapy with Cyanocobalamin is vital.

It is not known whether this medication will cause harm to an unborn baby, as insufficient studies have taken place. Patients who are pregnant or intending on becoming pregnant soon are advised to discuss the benefits and risks of using Cyanocobalamin with their doctor.

Cyanocobalamin is known to be excreted into breast milk and may cause harm to nursing babies. Patients who are currently breastfeeding are advised to consult their doctor, who may suggest stopping breastfeeding while taking this medication.


Cyanocobalamin vials should be stored at room temperature, away from heat and moisture. This medicine is therefore not suitable for storage in a bathroom and should be kept in a dedicated medicine cabinet if possible. It should not be frozen and should be kept out of reach of children and pets.

Unwanted or unused Cyanocobalamin should be disposed of in a safe and hygienic manner, and in accordance with local and state laws. Patients who are unsure of how to dispose of this medicine are advised to contact their local pharmacy or waste disposal department who will be able to offer advice. Some pharmacies may offer a Ĺ“take back scheme, where unwanted or expired medicines can be disposed of or recycled.


Cyanocobalamin is converted to vitamin B12 in the body and is an essential compound required for humans to exist. Treatment with this synthetic form of the compound is greatly beneficial to patients with B12 deficiency or pernicious anemia however, those who do not discuss their existing health conditions, allergies or medical history with their doctor may put themselves at risk during treatment with this medicine. Some medications may interact with Cyanocobalamin and cause adverse reactions, which is why is it necessary for patients to be upfront and forthcoming with their healthcare providers.

When administered correctly, Cyanocobalamin can relieve symptoms of B12 deficiency and pernicious anemia conditions which are difficult to treat in patients who have had all or part of the small intestine removed, or have conditions which prevent them from absorbing the vitamin from food intake.

To achieve the best possible results from this medicine, patient and doctor are advised to work together to determine the most appropriate dosage and frequency of use.