Vitamin B12 Deficiency: Symptoms, Causes and Treatment

Vitamin B12 deficiency can be easy to miss. You may first notice that ordinary tasks feel harder, your concentration is slipping or your feet keep tingling. Because the body stores vitamin B12, a problem with intake or absorption can continue for some time before clear symptoms develop.

What is vitamin B12?

Vitamin B12, also called cobalamin, is needed for normal red blood-cell formation, DNA synthesis and nervous-system function. The National Institutes of Health Office of Dietary Supplements explains that vitamin B12 occurs naturally in some foods, is added to fortified foods and is also available in supplements and prescription treatments.The body has to obtain vitamin B12 from dietary or supplemental sources, and absorbing it requires several steps involving the stomach and small intestine. This is why digestive conditions or surgery can sometimes lead to deficiency even when someone appears to consume enough B12.

What is vitamin B12 deficiency?

Vitamin B12 deficiency occurs when the body does not have enough available vitamin B12 to support normal blood-cell and nerve function. It can cause megaloblastic anaemia, but anaemia is not required for neurological symptoms to develop. The NICE guideline on vitamin B12 deficiency specifically advises clinicians not to rule out vitamin B12 deficiency simply because anaemia or unusually large red blood cells are absent. That matters when symptoms such as pins and needles, balance problems or cognitive changes are present.

Symptoms of vitamin B12 deficiency

Symptoms can develop gradually and vary from person to person.

Blood-related and general symptoms

• Persistent tiredness or weakness

• Breathlessness or palpitations when anaemia is present

• Pale or slightly yellow skin

• A sore or red tongue

• Reduced appetite or unexplained weight loss

Nervous-system and cognitive symptoms

• Pins and needles or numbness

• Problems with balance or walking

• Memory, concentration or thinking changes

• Visual symptoms

• Mood or psychological changes

These symptoms are not unique to vitamin B12 deficiency, so they cannot confirm the diagnosis on their own. However, new neurological symptoms deserve prompt assessment because prolonged deficiency can sometimes cause nerve damage that does not fully reverse. The NHS lists problems including pins and needles, memory changes, visual problems and impaired coordination among possible neurological complications.

Also read: 7 Everyday Habits That May Be Affecting Your Health

What causes vitamin B12 deficiency?

• Autoimmune gastritis: The immune system damages cells in the stomach involved in vitamin B12 absorption. NICE uses the term autoimmune gastritis for the underlying stomach condition rather than using pernicious anaemia as its name.

• Low dietary intake: Vitamin B12 occurs naturally mainly in animal-derived foods. People following vegan diets need a reliable source from fortified foods or supplements.

• Digestive conditions: Coeliac disease, Crohn’s disease and other conditions affecting the stomach or small intestine can reduce absorption.

• Gastrointestinal surgery: Bariatric surgery and operations involving the stomach or terminal ileum can interfere with vitamin B12 absorption.

• Medicines: Long-term metformin and some acid-reducing medicines can increase the risk of low vitamin B12 in some people.

• Recreational nitrous oxide: Nitrous oxide can inactivate vitamin B12 and cause neurological problems, even when a standard serum B12 result is not clearly low.

These causes matter because correcting a deficiency is not always as simple as eating more B12-rich foods. Someone who cannot absorb vitamin B12 properly may need a different treatment approach from someone whose intake is low.

Who is more likely to develop vitamin B12 deficiency?

Risk is higher in older adults, people following vegan diets without reliable fortified foods or supplements, people with autoimmune gastritis, coeliac disease or Crohn’s disease, and those who have had stomach or intestinal surgery. Long-term use of metformin or certain acid-reducing medicines can also increase risk, as can recreational nitrous oxide use. Vitamin B12 can become particularly relevant with age because absorbing it from food may become more difficult for some older adults. For a wider look at nutrients worth paying attention to later in life, see Aora’s guide to foods and nutrients to prioritise after 50.

How is vitamin B12 deficiency diagnosed?

A clinician may start with a total vitamin B12 or active B12 blood test, interpreted alongside symptoms and risk factors. When the first result is unclear, a methylmalonic acid test may help determine whether deficiency is more likely. Homocysteine can also be useful in some situations, although other factors such as folate deficiency can affect the result. When recreational nitrous oxide use is suspected, NICE recommends testing methylmalonic acid or homocysteine rather than relying on a standard serum B12 result alone. Treatment also should not always wait for every test result when there is a risk that neurological or haematological problems could deteriorate rapidly.

How is vitamin B12 deficiency treated?

Treatment depends on why the deficiency developed. Oral vitamin B12 may be suitable when dietary intake is the main problem and can also be used in some cases involving malabsorption. Intramuscular injections may be preferred when absorption is significantly impaired or when reliable oral treatment is unlikely. Some people need long-term or lifelong replacement. NICE recommends lifelong intramuscular vitamin B12 when autoimmune gastritis is the cause or suspected cause, and after a total gastrectomy or complete terminal ileal resection. Follow-up should consider whether symptoms are improving, whether treatment is being taken correctly and whether the underlying cause has been addressed.

Foods that contain vitamin B12

Vitamin B12 is naturally present in foods such as fish, meat, poultry, eggs, milk and other dairy products. Fortified breakfast cereals, some plant drinks and nutritional yeast can provide B12 for people who avoid animal foods, but the label should be checked because fortification varies between products. Diet can help prevent deficiency caused by inadequate intake, but it may not correct a deficiency caused by poor absorption. Someone with autoimmune gastritis, significant gastrointestinal surgery or another absorption problem may still need clinician-directed replacement.

Can vitamin B12 deficiency be prevented?

A varied diet can help prevent dietary deficiency when it includes reliable sources of vitamin B12. People following vegan diets generally need appropriately fortified foods or a regular B12 supplement because unfortified plant foods are not dependable sources. Prevention is different when absorption is the problem. People with autoimmune gastritis, significant malabsorption or certain forms of gastrointestinal surgery may need long-term or lifelong replacement regardless of how much B12 their diet contains.

Support your daily nutrition

Aora Nutrivit Plus provides 19 essential nutrients and grape seed extract to complement everyday nutrition when meals do not consistently cover nutritional needs. It is not a treatment for confirmed vitamin B12 deficiency, autoimmune gastritis or neurological symptoms, and it should not replace clinician-directed oral or injectable vitamin B12.

When should you see a doctor?

Seek prompt medical advice if you develop new pins and needles, numbness, balance or walking problems, visual changes, confusion or progressive weakness. Arrange an assessment if persistent fatigue or other possible symptoms occur alongside a recognised risk factor, such as a vegan diet without a reliable source of B12, a digestive condition, previous gastrointestinal surgery, long-term metformin or acid-reducing medicine use, or recreational nitrous oxide use. Early assessment matters because some neurological complications of prolonged vitamin B12 deficiency may not completely reverse even after the deficiency is treated.

Also read: 7 Best Foods to Eat After 50 for Strength and Healthy Ageing

Medical Disclaimer: This article is for general educational purposes only and should not replace professional medical advice, diagnosis or treatment. Seek prompt medical assessment for pins and needles, numbness, balance or walking problems, visual changes, confusion or progressive weakness. Do not delay clinician-directed treatment while trying general supplements.