Vitamin B12 Injections London: Symptoms, Testing, and Same-Day Treatment From a Private GP
Last updated: March 2026
The Online GP by The Wellness
If you are experiencing fatigue, brain fog, numbness, or tingling and suspect a vitamin B12 deficiency, The Online GP by The Wellness provides same-day blood testing and B12 injections at our Marylebone clinic. A consultation with blood test starts from £295. B12 injections start from £95 per injection as part of a consultation. All treatment is based on confirmed blood test results and clinical assessment. B12 injections are not administered without a clinical indication. All clinical decisions are at the sole discretion of the assessing doctor. All cases are accepted at the complete discretion of the clinic.
WhatsApp us for a same-day B12 consultation | Call 020 3951 3428 | Email team@thewellnesslondon.com
What are the symptoms of vitamin B12 deficiency?
Vitamin B12 deficiency is more common than most people realise. According to the British Society for Haematology, it affects approximately 6% of people under 60 and nearly 20% of people over 60 in the UK. Deficiency develops slowly, and symptoms are often attributed to other causes before the correct diagnosis is made.
Symptoms of B12 deficiency include persistent fatigue and low energy that does not improve with rest, cognitive difficulties including poor concentration, memory problems, and mental fog, numbness and tingling in the hands and feet (peripheral neuropathy), muscle weakness and difficulty with balance, a sore or unusually smooth tongue (glossitis), mouth ulcers, mood changes including irritability, depression, and anxiety, breathlessness and dizziness (due to anaemia), pale or yellowish skin, and heart palpitations.
If left untreated, severe B12 deficiency can cause permanent neurological damage. The peripheral neuropathy (numbness, tingling, and weakness) caused by B12 deficiency can become irreversible if the deficiency is prolonged. This is why early testing and treatment matter.
Experiencing these symptoms? WhatsApp us for a same-day blood test.
Who is at risk of B12 deficiency?
Certain groups are at significantly higher risk. Vegans and vegetarians are at risk because B12 is found almost exclusively in animal products (meat, fish, dairy, eggs). Without supplementation, vegans are highly likely to become deficient over time. The Vegan Society recommends that all vegans supplement B12. People over 50 are at increased risk because the ability to absorb B12 from food decreases with age due to declining stomach acid production. People with pernicious anaemia have an autoimmune condition that destroys the cells in the stomach that produce intrinsic factor, the protein needed to absorb B12. This is the most common cause of severe B12 deficiency in the UK. People taking certain medications are also at risk, as metformin (for diabetes), proton pump inhibitors (omeprazole, lansoprazole), and H2 receptor antagonists (ranitidine) all reduce B12 absorption. People with gastrointestinal conditions including Crohn's disease, coeliac disease, and those who have had gastric bypass surgery may have impaired absorption.
What blood tests diagnose B12 deficiency?
The Online GP offers a B12 assessment blood panel from £195 which includes serum vitamin B12 (the primary screening test), active B12 (holotranscobalamin, a more sensitive marker that detects deficiency earlier than serum B12), folate (deficiency often coexists with B12 deficiency and must be corrected simultaneously), full blood count (to check for macrocytic anaemia, the characteristic large red blood cells caused by B12 deficiency), and ferritin (iron stores, to exclude concurrent iron deficiency as a cause of symptoms).
If pernicious anaemia is suspected, additional testing includes intrinsic factor antibodies (positive in approximately 50-70% of pernicious anaemia cases) and gastric parietal cell antibodies.
Results are typically available within 24 to 48 hours. The doctor reviews the results with you, explains what they mean, and recommends the appropriate treatment. Not everyone with low-normal B12 needs injections. The doctor will determine whether supplementation, oral B12, or intramuscular injections are the right approach for your specific situation.
Do I need B12 injections or can I take tablets?
This is an important clinical question that depends on the cause and severity of the deficiency.
When injections are needed. Intramuscular B12 injections (hydroxocobalamin) are the standard treatment for pernicious anaemia (because the absorption pathway is impaired, oral supplements are insufficient), neurological symptoms (numbness, tingling, balance problems), and severe deficiency with significantly low serum B12. The standard NHS treatment protocol for B12 deficiency with neurological symptoms is hydroxocobalamin 1mg intramuscularly on alternate days until symptoms stop improving, then every two months for life.
When oral supplementation is sufficient. For dietary deficiency (vegans, vegetarians) without neurological symptoms, high-dose oral B12 (1000-2000mcg daily of cyanocobalamin) is effective. For mild deficiency without neurological involvement, oral supplementation is often the first-line approach. For maintenance after an initial loading course of injections.
The clinical decision. The doctor will determine the appropriate treatment based on your blood results, symptoms, and the likely cause of deficiency. Injections are not administered without a clinical indication. The Online GP does not offer B12 injections as a wellness or energy boost service for patients with normal B12 levels.
How much do B12 injections cost at a private GP in London?
Consultation and B12 blood panel from £295. Includes a video or in-person consultation with a GMC-registered doctor and the blood tests described above. This is the recommended starting point for any patient who suspects B12 deficiency.
B12 injection (hydroxocobalamin 1mg intramuscular) from £195 per injection. Administered at our Marylebone clinic. Injections are only administered following a clinical assessment and confirmed blood test results indicating deficiency.
Loading course of B12 injections (typically 6 injections over 2-3 weeks for neurological symptoms) from £450 for the course. The doctor determines the loading schedule based on clinical need.
Maintenance injections from £195 per injection. For patients with pernicious anaemia or other conditions requiring ongoing B12 replacement, maintenance injections are typically administered every 8-12 weeks. Regular blood monitoring is recommended.
Follow-up blood test from £195. Recommended 8-12 weeks after starting treatment to confirm B12 levels have normalised and to adjust the treatment plan if needed.
The clinic reserves complete discretion over whether treatment is clinically appropriate and over the final charge.
WhatsApp us for B12 testing and treatment
Can I get B12 injections without a blood test?
At The Online GP, no. We do not administer B12 injections without first establishing a clinical indication through a blood test and GP assessment. This is for your safety.
Administering B12 to a patient with normal levels provides no clinical benefit and may mask an underlying condition. Fatigue has dozens of causes, and assuming it is B12 deficiency without testing risks missing treatable conditions including thyroid disorders, iron deficiency, diabetes, and depression. A responsible GP investigates first and treats based on evidence.
If you have recent blood test results from another provider showing confirmed B12 deficiency, bring them to your consultation and the doctor can review them. A new blood test may not be needed if the results are recent and from an accredited laboratory.
The process
1. Contact us.WhatsApp, call 020 3951 3428, or email team@thewellnesslondon.com.
2. Consultation and blood test. A GMC-registered doctor conducts a clinical assessment and arranges the B12 blood panel. Blood is drawn at our Marylebone clinic.
3. Results review. Within 24-48 hours, the doctor contacts you with results and explains the findings. If B12 deficiency is confirmed, the doctor recommends the appropriate treatment.
4. Treatment. If injections are indicated, these are administered at our clinic. If oral supplementation is sufficient, the doctor advises on the correct product and dose.
5. Follow-up. Blood tests are repeated 8-12 weeks after starting treatment to confirm levels have normalised. The doctor adjusts the treatment plan accordingly.
Important information
B12 injections are a medical treatment, not a wellness service. The Online GP administers B12 injections based on confirmed clinical need. We do not offer B12 injections for general energy boosting or as part of a wellness menu for patients with normal B12 levels.
All clinical decisions are at the sole discretion of the assessing doctor.
Acceptance of cases is at the complete discretion of the clinic. Final charges are determined by clinical complexity.
All doctors are GMC-registered. The Online GP operates as part of The Wellness, a private medical clinic at 10 Portman Square, Marylebone, London.
Frequently asked questions about B12 injections
How quickly will I feel better after a B12 injection? Many patients notice an improvement in energy within a few days of starting treatment. Neurological symptoms (numbness, tingling) may take weeks to months to improve, and some damage may be permanent if the deficiency was prolonged. This is why early testing is important.
Can I self-inject B12 at home? Some patients with pernicious anaemia self-inject after training from a healthcare professional. The doctor can discuss this option and provide guidance if appropriate.
Are B12 injections painful? The injection is intramuscular, typically given into the upper arm or thigh. Most patients describe mild discomfort lasting a few seconds. The injection site may be slightly sore for a day.
Can vegans get enough B12 without injections? For dietary deficiency without neurological symptoms, high-dose oral B12 supplementation (1000-2000mcg daily) is usually effective. Injections are typically reserved for absorption problems or neurological involvement.
The Online GP by The Wellness 10 Portman Square, Marylebone, London Phone: 020 3951 3428 WhatsApp to book | Book online: thewellness.co.uk
Consultation and B12 blood panel from £295. B12 injections from £95. Loading course from £450. All treatment based on confirmed clinical need. Injections not administered without blood test results. All cases accepted at the discretion of the clinic. Final charges determined by clinical complexity.
