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Prescribing · UK

B12 injections, only if you actually need them.

The evidence-based case for hydroxocobalamin is narrow and well defined. If you have pernicious anaemia or another cause of malabsorption we prescribe the correct regimen for life. If you do not, we say so, and we test properly before anyone injects anything.

Our position

Test first. Treat the deficiency, not the marketing.

B12 injections are extensively marketed for energy, anti-ageing and immunity in patients whose B12 is normal. There is no good evidence they help in people who are not deficient. Repeat shots at £30 to £80 each add up quickly and buy no measurable benefit.

When B12 injections help

The narrow list of proven indications.

  • Pernicious anaemia

    Autoimmune destruction of parietal cells with positive intrinsic factor antibodies. Lifelong intramuscular hydroxocobalamin is the standard of care.

  • Post-gastrectomy or bariatric surgery

    Loss of intrinsic factor production means oral absorption is unreliable. IM replacement is usually needed indefinitely.

  • Terminal ileal Crohn’s or resection

    The terminal ileum is the sole site of active B12 absorption. Resection or active disease requires parenteral replacement.

  • Subacute combined degeneration of the cord

    Neurological B12 deficiency needs an intensified loading regimen (1 mg IM on alternate days until improvement) then quarterly maintenance.

  • Long-term strict vegan diet

    Dietary insufficiency confirmed on serum B12, active B12 or MMA. High-dose oral cyanocobalamin is often first line; IM is reserved for symptomatic or severe cases.

  • Chronic PPI, metformin or nitrous oxide exposure

    These reduce B12 absorption or oxidise stored cobalamin. Deficiency should be confirmed biochemically before treatment.

Assessment

What we test before anyone injects anything.

  • First-line bloods

    Serum B12, folate, ferritin, full blood count, TFTs, and coeliac serology if the presenting complaint is unexplained fatigue. Rules the common causes in or out.

  • Borderline serum B12 (150 to 250 ng/L)

    Reflex to active B12 (holotranscobalamin), methylmalonic acid and homocysteine. These clarify whether true tissue deficiency is present.

  • Suspected pernicious anaemia

    Anti-intrinsic factor antibodies (specific, less sensitive) and anti-parietal cell antibodies. A positive IF antibody confirms the diagnosis in the right clinical context.

  • Neurology and history

    Paraesthesia, gait disturbance or cognitive change with a low B12 warrants urgent IM loading and neurology review, not a monthly cosmetic shot.

Indicative pricing

What testing and prescribing costs privately.

If you are eligible for NHS treatment, hydroxocobalamin is prescribed free. Private cost only applies to the workup, the consultation and the injection administration.

Item Indicative range
B12 assessment panel (serum B12, folate, ferritin, FBC, TFT) £140–£210
Active B12 (holotranscobalamin) + MMA + homocysteine £180–£260
Pernicious anaemia antibody panel (IF + parietal cell) £120–£180
Single hydroxocobalamin 1 mg IM injection £30–£80
Loading course (6 injections over 2 weeks) £180–£320
Comprehensive fatigue workup + prescribed regimen £280–£550

Safety and evidence

What the evidence says, honestly.

  • Oral vs intramuscular

    For dietary deficiency without malabsorption, oral cyanocobalamin 1000 mcg daily is as effective as IM in randomised trials. Around 1 per cent is absorbed by passive diffusion, enough at that dose.

  • Injection side effects

    Local site pain, transient rash, and (rarely) anaphylaxis to cobalt or preservative. Cyanocobalamin should be avoided in Leber’s optic neuropathy.

  • The “energy boost” claim

    There is no good evidence that B12 injections improve energy, mood, cognition, weight or immunity in people who are not deficient. Repeat injections at £30 to £80 a time in a normal-B12 patient are hard to justify.

  • False reassurance

    Injecting B12 without a diagnosis can mask pernicious anaemia (by partially treating it) and delay the antibody testing that would confirm the true condition.

Frequently asked

Everything we get asked about B12 injections.

  • Should I be tested before I have a B12 injection?

    Yes. Serum B12 with folate, ferritin, full blood count and thyroid function is the sensible starting point. If serum B12 is borderline (150 to 250 ng/L), active B12 and methylmalonic acid clarify whether tissue deficiency is real. Intrinsic factor antibodies are added if pernicious anaemia is suspected. Injecting first, testing later, means you never know what you were treating.

  • Oral or intramuscular B12: which is better?

    For pernicious anaemia, post-gastrectomy and terminal ileal disease, IM hydroxocobalamin is standard because oral absorption is unreliable. For dietary deficiency in a vegan or a metformin user with an intact gut, oral cyanocobalamin 1000 mcg daily works as well as IM in randomised trials, and is cheaper and easier.

  • Does private health insurance cover B12 injections?

    Cover depends on documented deficiency and a specialist recommendation. Bupa, AXA and Vitality typically fund investigation and treatment where pernicious anaemia or another recognised cause is confirmed. Injections given for fatigue or wellness in a normal-B12 patient are almost never covered.

  • What are the signs of genuine B12 deficiency?

    Fatigue, breathlessness, glossitis, angular cheilitis, macrocytic anaemia, paraesthesia in the hands and feet, gait unsteadiness, cognitive slowing, and (in severe cases) subacute combined degeneration of the spinal cord. These need biochemical confirmation, not a trial of injections.

  • Do B12 injections give a genuine energy boost in normal people?

    No. Randomised evidence does not support B12 injections improving energy, mood or performance in people with normal B12 levels. The perceived lift is best explained by placebo, expectation and the ritual of the clinic visit. Save your money for a proper workup if you are tired.

  • What is the standard regimen for pernicious anaemia?

    Hydroxocobalamin 1 mg intramuscularly three times a week for two weeks (six loading doses), then 1 mg IM every three months for life. If neurological symptoms are present, loading is given on alternate days until no further improvement, and maintenance is every two months.

Ready to be tested properly?

Book the assessment, not the injection.

We confirm deficiency, identify the cause, and prescribe the right regimen. If you do not need injections, we will tell you.

Related

Related tests and treatments.

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