Feeling drained by mid-afternoon is so common that GPs have a shorthand for it: TATT, or “tired all the time”. Often the explanation is ordinary enough, such as poor sleep, stress or the long, dark run into winter. For some people, though, persistent fatigue is an early sign of something that can be measured and treated, and vitamin B12 deficiency is one of the most frequently overlooked causes.
Interest in B12 has grown alongside the wider wellness market, and vitamin injections are now offered by many private clinics as well as through GP surgeries. Used for the right reasons, they are a well-established and effective treatment. Used without a clear reason, they are unlikely to fix tiredness that has another cause. Knowing which group you fall into is the key to getting real value from them.
Why B12 matters
Vitamin B12 helps the body make healthy red blood cells and keeps the nervous system working properly. The NHS says adults need around 1.5 micrograms a day, which most people get from meat, fish, eggs, dairy and fortified foods. Because the liver stores a sizeable reserve, a deficiency usually develops slowly, sometimes over several years, and can go unnoticed for a long time.
Who is most at risk?
Low B12 is more common than many people assume. Figures cited alongside the 2024 NICE guideline suggest up to 6% of people under 60 in the UK have low levels, rising to around 20% in the over-60s.
The most common cause in the UK is an autoimmune condition, long known as pernicious anaemia and now described by NICE as autoimmune gastritis, in which the stomach can no longer absorb B12 from food. Eating more B12 will not help in these cases, which is why injections are the standard treatment and are often needed every two to three months for life.
Other groups to be aware of include:
- Vegans and some vegetarians, as B12 occurs naturally almost only in animal products. Studies report a very wide range of deficiency rates among vegans, so fortified foods or a supplement matter.
- People taking metformin. In 2022 the Medicines and Healthcare products Regulatory Agency (MHRA) classified low B12 as a common side effect of the diabetes medicine, potentially affecting up to one in ten users.
- Anyone on long-term acid-reducing medication, or who has had stomach or bowel surgery or a condition such as Crohn’s disease.
Signs worth taking seriously
Tiredness is only one symptom. The NHS also lists a sore or red tongue, mouth ulcers, pins and needles, muscle weakness, problems with vision, and changes in memory, concentration or mood. These can appear even before anaemia shows up in a blood count. The NHS warns that some problems caused by a long-term deficiency can become irreversible if left untreated, so symptoms like these are worth investigating rather than putting up with.
Practical steps before you book
If you are considering an injection, a little preparation goes a long way:
- Get tested first. A blood test gives a baseline. Results are not always clear-cut, so a good clinician will look at your symptoms as well as the number.
- Share your full picture. Mention your diet, any medication and relevant health conditions, as these help explain why your levels might be low.
- Check who is prescribing. B12 injections are prescription-only medicines in the UK, so a reputable provider should have a prescriber review your medical history before treatment, not simply book you in.
- Keep your GP informed. An injection may ease symptoms, but if an underlying condition such as autoimmune gastritis is driving the deficiency, it needs proper diagnosis and ongoing care.
Expectations matter too. Julian Owen, an Addenbrooke’s consultant and co-author of a BMJ summary of the NICE guidance, has noted that injections can restore normal metabolism and reverse complications, but that some symptoms may take months or even years to resolve fully.
The bottom line
Vitamin B12 injections are neither a miracle cure nor a gimmick. For people who are genuinely deficient, they can be life-changing, restoring energy and protecting long-term nerve health. For those whose levels are already healthy, they are unlikely to be the answer to feeling run down. The sensible route is to test, understand the cause and choose a properly regulated provider, so that any treatment you have is based on evidence rather than guesswork.
