Low Vitamin B12: Causes, Treatment and Prevention

Low vitamin B12 is fairly common in Australia, especially in older adults, vegans and people with some stomach or bowel conditions. It often comes on slowly, with tiredness, pins and needles or a sore tongue that are easy to put down to a busy life. This guide covers what B12 does, the signs of a deficiency, who should be checked, and how low vitamin B12 is treated and prevented.

Key takeaways

• Vitamin B12 keeps your blood cells and nerves healthy, and your body can't make it, so it has to come from food.
• An autoimmune stomach condition, a vegan diet, older age, bowel conditions and some long-term medicines are the usual causes.
• A blood test confirms it, and tablets or injections bring the level back up once the cause is known.
• Nerve damage can become permanent if a deficiency goes untreated for a long time, so see a doctor early.

What Vitamin B12 Does in Your Body

Vitamin B12, also called cobalamin, helps your bone marrow make healthy red blood cells, keeps your nerves working and helps turn food into energy. That is what vitamin B12 does for the body day to day. Your body stores several years' worth in the liver, so low vitamin B12 usually develops slowly.

Autoimmune disorders, such as pernicious anaemia, are a common cause in Australia, and B12 supplements or injections can correct the level once a doctor finds why it's low.

Benefits of Correcting a B12 Deficiency

Correcting a B12 deficiency usually brings your energy back within a few weeks, as your body starts making healthy red blood cells again and the anaemia clears. Treating the deficiency early also gives your nerves the best chance to recover, so pins and needles, numbness and balance problems often settle, although nerve damage from a long deficiency may not fully heal. Many people notice their memory, concentration and mood improve as well, and treatment brings down raised homocysteine, which is linked with blood vessel disease. In pregnancy, fixing a deficiency helps protect the baby's growing brain and nerves. If low vitamin B12 comes from your diet, B12-rich or fortified foods and a regular supplement help stop the deficiency coming back. If it comes from poor absorption, regular treatment keeps your level where it should be.

How a Lack of B12 Affects Blood and Nerves

Without enough B12, your bone marrow makes fewer red blood cells, and the ones it does make are large and immature, a pattern called megaloblastic anaemia. With fewer working red cells, less oxygen reaches your body, so you feel tired, short of breath and pale, often with muscle weakness. B12 also protects the fatty coating around your nerves, so when you're deficient, nerve signals slow down: pins and needles and numbness usually start in the feet and hands, and walking and balance can suffer. Low vitamin B12 can affect the brain too, with poor memory, low mood or confusion, and nerve problems can start before any anaemia shows. Because B12 is needed to clear homocysteine and methylmalonic acid, both build up in the blood, which a test can pick up. Many cases come from malabsorption, where the gut can't take B12 in, rather than a purely nutritional cause such as a vegan diet.

Regular B12 Checks for People at Higher Risk

Some people are more likely to become deficient and may need a B12 check from time to time, even before anything feels wrong. They include people over 65, vegans and some vegetarians, people with pernicious anaemia in the family or another autoimmune condition such as thyroid disease or type 1 diabetes, and people with autoimmune gastritis, coeliac disease or Crohn's disease. Weight loss surgery or other stomach surgery, chronic heavy drinking and some long-term medicines for diabetes or reflux also lower B12. Your doctor may check your cobalamin level, often alongside folate and a blood count, if you have fatigue that won't lift or numbness and tingling, and more regularly if you're at high risk. If you already have B12 injections, your doctor will tell you how often you still need a blood test.

Skin, Hair and Mouth Signs of Low B12

Low B12 often shows in the mouth first. The tongue can become sore, red and smooth, and some people get mouth ulcers, cracks at the corners of the lips or a burning feeling when they eat. The skin may look pale, or slightly lemon yellow, because of anaemia and the breakdown of fragile red cells. Less often, patches of darker skin appear, especially over the knuckles, and pernicious anaemia is linked with vitiligo, white patches where the skin loses its colour. Early greying and thinning hair have been reported, but both have many other causes. These signs usually fade once cobalamin levels are back to normal with supplements or injections. Older people who make less stomach acid, and people with coeliac disease or Crohn's disease, absorb B12 poorly, so skin and mouth changes alongside fatigue are a good reason for a blood test.

Vitamin B12 in Pregnancy and Breastfeeding

Your body needs a little more B12 when you're pregnant or breastfeeding: about 2.6 micrograms a day in pregnancy and 2.8 while breastfeeding, compared with 2.4 for other adults. Your baby's brain and nerves depend on it, and a fully breastfed baby gets B12 only from your milk, so a mother who is low can pass that on. A low level in pregnancy is linked with a higher chance of problems with the baby's spine and brain, and raised homocysteine is linked with some pregnancy complications.

Dietary sources of vitamin B12 include meat, fish, eggs, milk, cheese and yoghurt, and foods fortified with B12, such as some plant milks, breakfast cereals and yeast spreads. If you eat no animal foods, you'll need supplementation, and your doctor or midwife can advise on the dose; most pregnancy multivitamins contain some B12. Women with pernicious anaemia or a chronic bowel condition need their levels watched closely, because tiredness in pregnancy is common and the symptoms of lack of vitamin B12 are easy to miss. If a blood test in pregnancy shows a megaloblastic anaemia, your doctor checks for low B12 and other dietary causes.

If you're worried your baby isn't feeding, growing or developing as expected, see a GP in person or your child health nurse, as Medio's doctors see adults 18 and over.

Long Term Effects of Untreated B12 Deficiency

Left untreated, a B12 deficiency can impact your health in lasting ways. The longer the deficiency goes on, the more likely nerve damage is to become permanent: ongoing numbness, pain or weakness in the legs, unsteady walking and, rarely, damage to the spinal cord. Memory loss, depression and confusion can follow, and in older people the deficiency can look like dementia. Severe anaemia strains the heart, and raised homocysteine is linked with blood clots and blood vessel disease. People with pernicious anaemia also have a slightly higher risk of stomach cancer, so their doctor may suggest a look at the stomach lining.

How long does it take to correct B12 deficiency? Most people feel more energetic within a few days to a few weeks of starting treatment, and the blood count is usually back to normal within about two months. Nerves recover more slowly, over months, and may not fully recover if the deficiency was long or severe. That's why the symptoms of lack of vitamin B12 are worth taking seriously early, even when they seem mild.

Common Symptoms of a B12 Deficiency

The most common signs and symptoms of vitamin B12 deficiency are tiredness, lack of energy, breathlessness, a racing heart with effort and pale skin, mostly from anaemia. Nerve symptoms include pins and needles, numbness, a burning feeling in the feet, clumsiness, trouble with balance and, sometimes, changes in vision. Mental symptoms include poor memory, irritability, low mood and, when it's severe, confusion.

Symptoms can come on so slowly that you get used to them. Many of them also fit iron deficiency, thyroid problems, depression or simply being run down, which is why a blood test is the only way to know. Your doctor will usually check B12 with folate, because a folate deficiency causes the same kind of anaemia, and may add a homocysteine test if the result is borderline. Taking high-dose folic acid alone can hide the anaemia of a B12 deficiency while nerve damage carries on, so ask your doctor before you start it. Call 000 or go to an emergency department for chest pain, fainting, severe breathlessness or sudden confusion.

Summary

This guide covered what B12 does, the signs and long-term effects of low vitamin B12, who should be checked and how it's treated. If you're worried about low vitamin B12, a Medio GP can talk through your symptoms by phone, request a blood test if they think you need one, and advise on treatment or send an eScript if it's right for you.

Frequently asked questions

What do you do if you are low in B12?

If you have low vitamin B12, see your doctor, who will look for the cause, because how B12 deficiency is treated depends on it. If it's your diet, B12 tablets and more B12-rich or fortified foods usually fix it. If your body can't absorb B12, you'll usually need injections, which need a prescription in Australia, or high-dose tablets your doctor advises. Are there other ways to get vitamin B12? A tablet that dissolves under the tongue works about as well as one you swallow.

What are the symptoms of a vitamin B12 deficiency?

The main ones are tiredness, breathlessness, pale skin, a sore red tongue, pins and needles or numbness in the hands and feet, poor balance, and changes in memory or mood. What does a B12 deficiency look like? Often like ordinary exhaustion at first, which is why a blood test is needed to confirm it.

How long does it take to correct B12 deficiency?

Energy often picks up within a few days to two weeks of starting treatment, and blood counts usually return to normal within about eight weeks. Pins and needles and numbness can take six to twelve months to improve, and some may stay if the damage was long-standing. Your doctor will repeat your blood test to check the treatment is working.

What are the four stages of vitamin B12 deficiency?

Doctors sometimes describe four stages. First, B12 levels in the blood fall. Second, the body's stores run down. Third, the cells run short and homocysteine builds up in the blood. Fourth, anaemia and nerve problems appear. Treating it at an earlier stage helps protect your long-term health and prevent lasting nerve damage.

What do you crave when your B12 is low?

Low B12 doesn't cause a particular craving, and many people lose their appetite instead. Craving ice or other things that aren't food is more often linked with low iron. If you feel tired and have unusual cravings, ask your doctor about a blood test that checks for both, so you know which one you're short of.

What are the facial signs of B12 deficiency?

Facial signs include pale or slightly yellow skin, a sore, smooth, red tongue, cracks at the corners of the mouth and mouth ulcers. What causes vitamin B12 deficiency? Most often a stomach condition that stops B12 being absorbed, a vegan diet, older age, bowel conditions, stomach surgery or some long-term medicines, so your doctor looks for the cause as well as the signs.