Hydroxocobalamin (Vitamin B12 injection)
Pronunciation: hy-DROX-oh-koh-BAL-a-min.
- Generic name
- hydroxocobalamin
- Drug class
- Water-soluble vitamin (B-complex); haematinic/neurotrophic agent
- Form
- Solution for injection, typically 1 mg/mL (1000 mcg/mL)
- Route
- Intramuscular injection, given by a healthcare professional (the intravenous route is avoided for this specific low-dose B12-deficiency product)
- Legal status
- Prescription-only medicine in every market where it is currently authorised
Availability and supply rules vary by country
Trade names by country: United States · United Kingdom · Canada · Australia · New Zealand
Australia: HYDROXO-B12 / VITA-B12 / COBAL-B12 / NEO-B12 injection (generic hydroxocobalamin) (5) · Full directory
What hydroxocobalamin is and how it works
Hydroxocobalamin is a form of vitamin B12 given as an intramuscular injection to treat diagnosed vitamin B12 deficiency, most importantly pernicious anaemia (a condition where the body cannot absorb B12 from food due to a lack of intrinsic factor, a protein made in the stomach). It works faster than oral B12 and bypasses any gut-absorption problem. (1) (2)
If your clinician has diagnosed you with vitamin B12 deficiency or pernicious anaemia, you may be prescribed this injectable form of vitamin B12. It requires a diagnosis, a prescription, and ongoing follow-up, and in true pernicious anaemia it is usually needed for the rest of your life to prevent the anaemia and nerve damage from returning.
Mechanism of action: how hydroxocobalamin works
Hydroxocobalamin is a cobalamin (vitamin B12) form used therapeutically as an essential cofactor for methionine synthase and L-methylmalonyl-CoA mutase, required for DNA synthesis, red blood cell maturation, and myelin maintenance. Intramuscular administration bypasses the intrinsic-factor-dependent gut absorption step that fails in pernicious anaemia. (1) (2)
What hydroxocobalamin is used for
Pernicious anaemia and diagnosed vitamin B12 deficiency
Used to treat pernicious anaemia (with or without neurological involvement) and other causes of diagnosed vitamin B12 deficiency, including dietary deficiency (e.g. strict vegetarian/vegan diets), malabsorption syndromes, reduced intrinsic factor, and other absorption problems. (1) (2) (5) (6)
Tobacco amblyopia and Leber's hereditary optic atrophy (UK-specific use)
In the UK, hydroxocobalamin injection is also indicated for tobacco amblyopia (a specific type of vision loss) and Leber's hereditary optic atrophy -- note this is the opposite of cyanocobalamin, which must not be used in Leber's disease because it can worsen it. (2)
Schilling Test (United States)
A flushing dose of hydroxocobalamin is used as part of the Schilling Test, a diagnostic test for vitamin B12 absorption. (1)
Before taking hydroxocobalamin
Do not take / not appropriate for
- Do not receive this injection if you have had an allergic (hypersensitivity) reaction to hydroxocobalamin or any ingredient in the product. (all countries) (1) (2)
Tell your clinician about
- Whether you have been diagnosed with pernicious anaemia or another confirmed cause of vitamin B12 deficiency.
- Any history of allergic reaction to vitamin B12 or related compounds.
- Whether you take chloramphenicol (an antibiotic) or have iron or folic acid deficiency, as these can affect how well treatment works.
- Whether you are or could be pregnant, or are breastfeeding.
- Any history of polycythaemia vera (a blood disorder), as treatment may unmask this condition.
- Any other supplements or medicines you take, including folic acid.
How to take hydroxocobalamin
- This injection is given only by a healthcare professional, by intramuscular injection -- the intravenous route is avoided for this specific product.
- Do not switch yourself from a prescribed injectable regimen to an oral supplement, or ask the prescriber about stopping it, without talking to your prescriber -- in true pernicious anaemia, stopping treatment allows the anaemia and nerve damage to return.
- The product should be protected from light.
Procedures and treatment changes
Tell the treating team before surgery, procedures, or any medicine change. Do not alter treatment without the responsible clinician. (1) (2) (3) (4) (5) (6)
Missed dose
Contact your prescriber's clinic for guidance on rescheduling a missed injection appointment -- do not attempt to make up for a missed dose yourself.
Overdose
Because this injection is only given under medical supervision, seek urgent medical attention for any signs of an allergic reaction, unusual swelling, or feeling unwell after a dose. (1)
Side effects
Side effects and their urgency vary; report severe, persistent, or concerning symptoms.
Injection-site pain.
What to notice: Injection-site pain.
What to do: Discuss persistent or troublesome symptoms with the treating clinician or pharmacist. (1)
Mild, transient itching, feeling of body swelling, or diarrhoea.
What to notice: Mild, transient itching, feeling of body swelling, or diarrhoea.
What to do: Discuss persistent or troublesome symptoms with the treating clinician or pharmacist. (1) (2)
Transitory skin rash.
What to notice: Transitory skin rash.
What to do: Discuss persistent or troublesome symptoms with the treating clinician or pharmacist. (1)
Serious warnings
Signs of a serious allergic reaction — emergency
Symptoms: Swelling of the face, lips, tongue, or throat; difficulty breathing; widespread rash or hives; sudden collapse.
Action: Seek emergency medical help immediately -- anaphylaxis has been reported, though it is rare. (1)
Low blood potassium (hypokalaemia) during early treatment — high caution
Symptoms: Palpitations, muscle weakness, or an irregular heartbeat, especially in the first 48 hours of treatment for severe anaemia.
Action: Rapid correction of severe megaloblastic anaemia can cause a sudden drop in blood potassium, which has been linked to dangerous heart rhythm problems; your prescriber will monitor your potassium levels closely during this period. (1) (2)
Untreated pernicious anaemia (stopping treatment) — high caution
Symptoms: Return of tiredness/anaemia symptoms, or new numbness, tingling, balance problems, or memory/thinking changes.
Action: Do not stop prescribed injections on your own -- in true pernicious anaemia, stopping treatment allows the anaemia to return and can lead to irreversible spinal cord and nerve damage. Contact your prescriber with any concerns about your treatment. (1)
Unmasking of polycythaemia vera — high caution
Symptoms: New symptoms such as headache, dizziness, or unusual flushing during treatment.
Action: Vitamin B12 treatment can occasionally unmask an underlying blood condition called polycythaemia vera. Report any new or unusual symptoms to your prescriber. (1)
Interactions
- Chloramphenicol (an antibiotic) and other bone-marrow suppressants may reduce the effectiveness of hydroxocobalamin's response in treating anaemia. (1) (2)
- Concurrent iron or folic acid deficiency can impede the therapeutic response to treatment -- your clinician may check and treat these together. (1)
- Oral contraceptives can modestly lower serum vitamin B12 concentrations, though this is generally not considered clinically significant. (2)
- High-dose folic acid cannot substitute for vitamin B12 treatment -- using folic acid alone in a B12-deficient patient can correct the blood count while allowing irreversible neurological damage to progress unrecognised. (1)
Pregnancy, breastfeeding, kidney/liver function, age
Pregnancy
Should not be used to treat megaloblastic anaemia of pregnancy specifically, as a different underlying mechanism applies there -- any diagnosed B12 deficiency in pregnancy should be discussed with your prescriber. (1) (2) (3) (4) (5) (6)
Breastfeeding
Considered safe at normal therapeutic doses -- unlikely to harm a nursing infant. (1) (2) (3) (4) (5) (6)
Children
Paediatric dosing (e.g. 1-5 mg total over 2 or more weeks in 100 mcg doses, then 30-50 mcg every 4 weeks) should be managed by a paediatric specialist. (1) (2) (3) (4) (5) (6)
Elderly
Older adults are at higher risk of vitamin B12 deficiency due to reduced stomach acid production (atrophic gastritis) impairing absorption from food, even without pernicious anaemia. (1) (2) (3) (4) (5) (6)
Hepatic_impairment
No specific dose adjustment is described in the sources reviewed for liver impairment. (1) (2) (3) (4) (5) (6)
Renal_impairment
No specific dose adjustment is described in the sources reviewed for kidney impairment. (1) (2) (3) (4) (5) (6)
Source_ids
US-DAILYMED-HYDROXOCOBALAMIN-INJ-2026,UK-EMC-HYDROXOCOBALAMIN-2026 (1) (2) (3) (4) (5) (6)
Monitoring
Before starting
- Confirmation of the diagnosis (vitamin B12 deficiency or pernicious anaemia) before starting treatment -- not simply assumed
- Baseline full blood count
- Baseline potassium level in patients with severe anaemia
During treatment
- Serum potassium monitoring during the first 48 hours of treatment, especially for severe anaemia.
- Full blood count monitoring until values normalise, then periodically during lifelong maintenance treatment for pernicious anaemia.
- Watch for signs of an emerging blood disorder (polycythaemia vera) during treatment.
Storage
Stored and handled by healthcare professionals according to the product's labelling -- commonly protected from light.
Professional information
Clinician-facing context only, sourced from the current US FDA DailyMed hydroxocobalamin injection label and the UK emc hydroxocobalamin SmPC; verify against the current full label in the relevant jurisdiction before prescribing. This product is distinct from Cyanokit (high-dose IV hydroxocobalamin for cyanide poisoning).
United States
Indication: Pernicious anaemia and other B12-deficiency malabsorption states; Schilling Test
Dose summary: 30 mcg daily x5-10 days then 100-200 mcg monthly maintenance; higher doses for serious illness/neurological involvement; IM only, avoid IV route for this product.
Renal context: Not specifically established in the source reviewed for this dossier. (1)
United Kingdom
Indication: Pernicious/macrocytic anaemia, tobacco amblyopia, Leber's optic atrophy
Dose summary: Without neurological involvement: 250-1000 mcg IM alternate days x1-2 weeks, then weekly until normalised, then 1000 mcg every 2-3 months maintenance. With neurological involvement: 1000 mcg alternate days initially, same maintenance.
Renal context: Not specifically established in the source reviewed for this dossier. (2)
Hepatic guidance
No specific hepatic dose adjustment described in the sources reviewed.
Overdose note
Vitamin B12 injectables have a wide margin of safety at these low, replacement-range doses; overdose experience is limited and management is supportive. This is entirely separate from the very different high-dose IV Cyanokit product's own dosing and toxicity profile. (1) (2)
Frequently asked questions
Is this the same as the hydroxocobalamin used for cyanide poisoning (Cyanokit)?
No. This page covers the low-dose (micrograms) intramuscular injection used to treat diagnosed vitamin B12 deficiency and pernicious anaemia. Cyanokit is a completely different product: a very high dose (grams) given rapidly by intravenous infusion as an emergency antidote for cyanide poisoning. The dose, route, and use are entirely different -- do not confuse the two. (1) (4)
Why do I need this injection instead of an oral B12 tablet?
People with pernicious anaemia lack intrinsic factor, a stomach protein needed to absorb B12 from food or oral tablets, so an injection that bypasses the gut is used instead. People with certain gut surgeries or malabsorption conditions may also need injections for the same reason. (1) (2)
Is hydroxocobalamin safe if I have Leber's hereditary optic atrophy?
Hydroxocobalamin is actually the UK-indicated treatment for Leber's optic atrophy, unlike cyanocobalamin (a different B12 form used in some countries, including the US), which must not be used in this condition because it can cause severe, swift optic nerve damage. Always confirm which form of B12 you are being given. (2)
Is this injection available everywhere?
It is currently authorised in the United States, United Kingdom, European Union, Australia, and New Zealand. In Canada, live regulator data shows no vitamin-B12-context hydroxocobalamin injectable is currently marketed (older products are dormant or cancelled) -- other forms of injectable vitamin B12 remain available there instead. Ask your local pharmacist or prescriber about what is currently available in your country. (4)
What is the mechanism of action of hydroxocobalamin?
Hydroxocobalamin is a cobalamin (vitamin B12) form used therapeutically as an essential cofactor for methionine synthase and L-methylmalonyl-CoA mutase, required for DNA synthesis, red blood cell maturation, and myelin maintenance. Intramuscular administration bypasses the intrinsic-factor-dependent gut absorption step that fails in pernicious anaemia. (1) (2)
What is the generic name of Hydroxocobalamin (Vitamin B12 injection)?
References
- HYDROXOCOBALAMIN injection, solution -- prescribing information (vitamin B12 deficiency product, distinct from Cyanokit)U.S. Food and Drug Administration / DailyMed (NIH) · United States · accessed 2026-07-31 · source 1
- Hydroxocobalamin 1mg/ml Solution for Injection -- Summary of Product Characteristicselectronic medicines compendium (emc), United Kingdom · United Kingdom · accessed 2026-07-31 · source 2
- Injectable hydroxocobalamin/cyanocobalamin medicinal products -- national marketing authorisation across EU member statesEuropean Union medicines regulation (Directive 2001/83/EC, national marketing authorisation route) · European Union · accessed 2026-07-31 · source 3
- Hydroxocobalamin products in the Health Canada Drug Product Database (live API)Health Canada Drug Product Database (live API query) · Canada · accessed 2026-07-31 · source 4
- HYDROXO-B12, VITA-B12, COBAL-B12, NEO-B12 injection -- ARTG entriesTherapeutic Goods Administration (TGA), Australia -- Australian Register of Therapeutic Goods (ARTG) · Australia · accessed 2026-07-31 · source 5
- Neo-B12 Injection and Hydroxocobalamin Panpharma -- New Zealand Data SheetsMedsafe (New Zealand Medicines and Medical Devices Safety Authority) · New Zealand · accessed 2026-07-31 · source 6
Brand names by country
Single-ingredient hydroxocobalamin names are shown separately by country. Product availability, strengths, and supply rules can change; combination products are not included here.
Priority countries
United States
- Cyanokit5 g/250mL · btg international inc.
United Kingdom
- Cobalin-H / hydroxocobalamin injection (generic) (2)MHRA licensed emc smpc confirmed prescription injectable · 1 mg/mL · multiple UK marketing authorisation holders
Canada
- HYDRO COBEX INJ
- CYANOKIT
Australia
- HYDROXO-B12 / VITA-B12 / COBAL-B12 / NEO-B12 injection (generic hydroxocobalamin) (5)TGA ARTG registered confirmed prescription injectable · 1 mg/mL · Aspen Pharmacare Australia Pty Ltd; Amdipharm Mercury Australia Pty Ltd; Pfizer Australia Pty Ltd
New Zealand
- Neo-B12 Injection / Hydroxocobalamin Panpharma (6)Medsafe approved confirmed prescription injectable · 1 mg/mL (1000 microgram/mL) · multiple Medsafe-approved sponsors, e.g. Panpharma
View brands in additional countries.
European Union
Hydroxocobalamin injection (nationally authorised generics, various EU brand names) (3)