Vitamin B12 deficiency symptoms: the signs, the causes and the tests

Questions people ask

• What are the first signs of vitamin B12 deficiency?

  Often tiredness and low energy come first, then breathlessness, a sore red tongue or mouth ulcers. Some people first notice pins and needles or numbness in their hands or feet, sometimes before any anaemia. Because symptoms build slowly over months, they're easy to put down to stress or age. A blood test is the way to know.

• What does low vitamin B12 do to the body?

  B12 is needed to make red blood cells and to keep the nerves and brain healthy. When it runs low, you can develop anaemia, with tiredness and breathlessness, and nerve problems such as tingling, numbness, weakness and poor balance. It can also affect memory and mood. Anaemia usually recovers with treatment; nerve damage may not if treatment is late.

• What is a normal vitamin B12 level?

  Labs differ. NICE in the UK treats a total B12 below 180 ng/L as confirmed deficiency, 180 to 350 as possible deficiency needing more checks, and above 350 as deficiency unlikely. MedlinePlus lists about 299 to 1054 pg/mL as a normal range (1 ng/L equals 1 pg/mL). Always compare with the range on your own report.

• Can B12 deficiency cause tingling in the hands and feet?

  Yes. Pins and needles, numbness or a burning feeling in the hands and feet are common nerve symptoms of low B12, and they can appear before any anaemia. Because nerve damage can become permanent if treatment is delayed, tingling or numbness is a reason to see a doctor and ask for a B12 test within a week or so.

• Can low B12 cause anxiety, depression or memory loss?

  It can contribute. Low B12 is linked to low mood, irritability, poor memory and difficulty thinking clearly, and in severe cases confusion. These symptoms have many other causes too, so a B12 test is one sensible check, especially in older adults or vegetarians. If you have thoughts of harming yourself, get help now.

• Who is most likely to be low in vitamin B12?

  Vegans and vegetarians who eat little dairy, older adults, people with pernicious anaemia or other autoimmune conditions, people with coeliac or Crohn's disease or past stomach or bowel surgery, and people taking metformin or acid-reducing medicines long term. Pregnant and breastfeeding women with low intake are also at risk, and so are their babies.

• Does metformin cause vitamin B12 deficiency?

  Long-term metformin use can lower B12 levels in some people, and NICE lists it as a risk factor. Don't stop metformin because of this: it's an important diabetes medicine. Instead, ask your doctor whether a B12 test makes sense, especially if you notice tingling, numbness or tiredness. The same applies to long-term acid-reducing medicines.

• Which foods are high in vitamin B12?

  Milk, yoghurt, cheese, eggs, fish, meat and shellfish are natural sources. For vegans and people who eat little dairy, fortified foods such as some plant milks, breakfast cereals and nutritional yeast help, or a B12 supplement. A pharmacist can help you choose. If you already have a deficiency, diet alone may not be enough: your doctor will advise.

• How is vitamin B12 deficiency treated?

  Doctors treat it with B12 injections or tablets, depending on the cause and how severe it is. If the gut can't absorb B12, as in pernicious anaemia, injections are usually needed, often for life. Your doctor decides the form and schedule. Nerve symptoms are treated promptly, and blood tests are repeated to check it's working.

• How long does it take to recover from B12 deficiency?

  Many people feel more energetic within days to weeks of starting treatment, and the blood count usually recovers over a couple of months. Nerve symptoms can take longer, often months, and may not fully recover if they were present for a long time before treatment. That's why it's worth getting tested early.

• Is B12 deficiency the same as low iron?

  No, though both cause anaemia, so both can make you tired, breathless and pale. Low B12 tends to make red cells large (high MCV) and can cause nerve and mouth symptoms; low iron makes red cells small (low MCV) and can cause brittle nails or craving ice. Some people have both. Blood tests tell them apart.

• Can I take folic acid instead of B12?

  Not without a B12 test first. Folic acid can correct the blood count in B12 deficiency while nerve damage carries on unnoticed. That's why doctors check B12 and folate together and treat B12 deficiency before or alongside folate deficiency. Ask your doctor or pharmacist before starting either.

• Does vitamin B12 deficiency matter in pregnancy?

  Yes. A mother low in B12 can pass the shortage to her baby, and babies low in B12 can become unwell, with poor feeding or slow development. If you're pregnant or breastfeeding and vegetarian or vegan, or have other risk factors, tell your doctor or midwife and ask about B12. Don't start or change supplements without advice.