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( Vitamin B 12 )

Pronunciation: SYE-an-oh-koe-BAL-a-min
Class: Water-soluble vitamin

Trade Names

- Injection, solution 1,000 mcg/mL

- Spray, intranasal 500 mcg per 0.1 mL

Rapid B-12 Energy
- Spray, sublingual 200 mcg/spray

Twelve Resin-K
- Tablets, oral 1,000 mcg

Vitamin B 12
- Tablets, oral 50 mcg
- Tablets, oral 100 mcg
- Tablets, oral 500 mcg
- Tablets, oral 1,000 mcg
- Tablets, sublingual 500 mcg
- Tablets, sublingual 1,000 mcg
- Tablets, sublingual 2,500 mcg
- Tablets, sublingual 5,000 mcg
- Tablets, sublingual 6,000 mcg
- Lozenges, oral 50 mcg
- Lozenges, oral 100 mcg
- Lozenges, oral 250 mcg
- Lozenges, oral 500 mcg


Involved in protein synthesis; vitamin B 12 is essential to growth, cell reproduction, hematopoiesis, and nucleoprotein and myelin synthesis.



Rapidly absorbed. T max is 1 h (IM) and 1.25 h (intranasal). C max is approximately 757.96 pg/mL (intranasal).


Bound to intrinsic factor during transit through the stomach; separation occurs in the presence of calcium, and vitamin B 12 enters the mucosal cells for absorption. Bioavailability is approximately 25%.


Distributed and stored primarily in the liver and bone marrow. In the blood, it is bound to transcobalamin II.


Unbound vitamin B 12 is rapidly eliminated in the urine.


50% to 98% is excreted in the urine within 48 h.

Indications and Usage

Vitamin B 12 deficiency; malabsorption syndrome of various causes (eg, pernicious anemia; GI pathology dysfunction or surgery including gluten enteropathy, small bowel bacterial overgrowth, and total or partial gastrectomy; fish tapeworm infestation; malignancy of pancreas or bowel; folic acid deficiency); supplementation because of increased requirements (eg, associated with pregnancy, thyrotoxicosis, hemolytic anemia, hemorrhage, malignancy, hepatic and renal disease); vitamin B 12 absorption test (eg, Schilling test).


Hypersensitivity to cobalt, vitamin B 12 , or any component of these medications.

Dosage and Administration

Recommended Dietary Allowance
Adults and Children 14 y and older

PO or SL 2.4 mcg/day.

Children 9 to 13 y of age

PO or SL 1.8 mcg/day.

Children 4 to 8 y of age

PO or SL 1.2 mcg/day.

Children 1 to 3 y of age

PO or SL 0.9 mcg/day.

Pregnancy (14 to 50 y of age)

PO or SL 2.6 mcg/day.

Lactation (14 to 50 y of age)

PO or SL 2.8 mcg/day.

Adequate Intake for Children 7 to 12 mo of age

0.5 mcg/day.

Adequate Intake for Children 0 to 6 mo of age

0.4 mcg/day.

Dietary Supplement

PO or SL 50 to 6,000 mcg/day.

Vitamin B 12 Deficiency
Adults Intranasal

1 spray (500 mcg) in 1 nostril once weekly.

IM/deep subcutaneous

100 mcg/day for 6 to 7 days. If reticulocyte response occurs, give 100 mcg every other day for 7 doses, then give 100 mcg every 3 to 4 days for 2 to 3 wk. After this regimen, give 100 mcg/mo for life.

Children Intranasal

Dose should be in the amount recommended by the Food and Nutrition Board, National Academy of Sciences-National Research Council.

IM/deep subcutaneous

0.5 to 3 mcg/day.

Shilling Test Flushing Dose

IM 1,000 mcg.

General Advice

  • Injection
  • For IM or deep subcutaneous injection. Avoid using the IV route.
  • Coadminister with folic acid, if needed.
  • Contains benzyl alcohol. Benzyl alcohol has been associated with a fatal gasping syndrome in premature infants.
  • Oral
  • For sublingual tablets, place under tongue for 30 sec before swallowing or until dissolved.
  • For lozenges, let dissolve in mouth before swallowing; may also be swallowed whole.
  • Shake the spray well before using.
  • Administer tablets with a meal.
  • Twelve Resin-K tablets may be taken orally, sublingually, or buccally.
  • Intranasal
  • Administer at least 1 h before or 1 h after ingestion of a hot food or liquid.
  • Pump must be primed before each use.


Store between 59° and 86°F. Protect injection from light and freezing. Store the nasal spray upright covered in carton until ready to use. Discard nasal spray after the eighth dose.

Drug Interactions


Decreases hematologic effects of vitamin B 12 in patients with pernicious anemia.

Colchicine, excessive alcohol intake (more than 2 wk), para-aminosalicylic acid

Decreases GI absorption of vitamin B 12 .


Hot foods may cause nasal secretions, resulting in loss of medication administered intranasally; therefore, administer intranasal doseform at least 1 h before or after ingestion of hot foods or liquids.

Laboratory Test Interactions

Methotrexate, pyrimethamine, and most antibiotics

May invalidate vitamin B 12 or folic acid diagnostic microbiological blood assays. May mask the true diagnosis of megaloblastic anemia or folate deficiency.

Adverse Reactions


Peripheral vascular disorder (1%); CHF; peripheral vascular thrombosis; pulmonary edema.


Headache (11%); asthenia (4%); dizziness, nervousness (3%); incoordination (2%); abnormal gait, anxiety, hypoesthesia, paresthesia (1%).


Itching, transitory exanthema.


Rhinitis (2%).


Dyspepsia (2%); glossitis, nausea, nausea and vomiting, vomiting (1%); mild transient diarrhea.


Arthritis (2%); back pain, myalgia (1%).


Dyspnea (1%).


Infection (4%); generalized pain (3%); anaphylactic shock, death, feeling of swelling of entire body, polycythemia vera.



Obtain all hematologic parameters, including hematocrit, reticulocyte count, vitamin B 12 , folate, and iron levels, as well as potassium, prior to treatment. Monitor vitamin B 12 concentrations and CBC 1 mo after starting treatment and at 3- to 6-mo intervals thereafter. Monitor for carcinoma of the stomach as indicated. Carefully monitor serum potassium levels and platelet count during therapy.


Category A ( Category C in doses that exceed the RDA, intranasal, injection).


Excreted. The American Academy of Pediatrics classifies vitamin B 12 as compatible with breast-feeding.


Injection may contain benzyl alcohol, which has been associated with fatal “gasping syndrome” in premature infants.


Anaphylactic shock and death have been associated with parenteral use.

Special Risk Patients

Infection, uremia, concurrent iron or folic acid deficiency, and drugs with bone marrow–suppressant properties may blunt the therapeutic response to cyanocobalamin.


Parenteral form contains aluminum that may be toxic, especially in patients with renal impairment.

Folate deficiency

Treatment with vitamin B 12 may produce hematologic response in these patients, masking the true diagnosis.

Leber disease

Patients with early Leber disease (hereditary optic nerve atrophy) suffered severe and rapid optic atrophy when treated with cyanocobalamin.

Nasal conditions

Nasal administration has not been evaluated in patients with nasal congestion, allergic rhinitis, upper respiratory tract infections, or other nasal pathologies.

Polycythemia vera

May unmask the signs of suppressed polycythemia vera.

Severe megaloblastic anemia

Hypokalemia and thrombocytosis could occur upon conversion of severe megaloblastic to normal erythropoiesis with vitamin B 12 ; sudden death may occur with intense treatment.



Overdosage has not been reported.

Patient Information

  • Advise patients with pernicious anemia of the need to continue therapy throughout lifetime.
  • Instruct patients to administer the nasal spray at least 1 h before or 1 h after ingestion of hot foods or liquids.
  • Advise patient with nasal congestion, allergic rhinitis, or upper respiratory tract infection to defer treatment with intranasal spray until symptoms have subsided.
  • Teach patient of need to maintain well-balanced diet. Remind patient of the following good sources of vitamin B 12 : seafood, egg yolks, organ meats, fortified breakfast cereals, meat, cheeses, milk, or other dairy products.
  • Advise patient that folic acid is not a substitute for vitamin B 12 but may be taken concurrently.
  • Apprise vegetarians who do not consume animal products of the need for daily oral vitamin B 12 .
  • Instruct patients using intranasal form on the method for priming the pump.
  • Inform patient with pernicious anemia of need to have periodic GI evaluations.
  • Instruct patient to report the following symptoms to their health care provider: irregular heartbeat, muscle weakness, shortness of breath, vision disturbances.

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