Vitamin B12 deficiency: who's at risk and why it matters

Vitamin B12 is important for our overall health but you may be getting less than you need without realising it. 

It can be harder to absorb as you age, and those on vegan diets may find it trickier to get enough too. 

We explain why it's important to ensure you're getting enough, possible symptoms of deficiency, and how to top up levels if needed.

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Symptoms of vitamin B12 deficiency

According to the NHS, low B12 levels can cause a range of symptoms, including those that affect your brain and nervous system, such as confusion and memory issues. These include:

• Pale or jaundiced skin
• Extreme tiredness and lack of energy
• Pins and needles, muscle weakness, cramping, impaired balance
• Cognitive issues such as anxiety, depression, 'brain fog', psychosis and dementia
• Red, inflamed tongue 
• Blurred vision

What does vitamin B12 do?

Vitamin B12 is needed to keep the nervous system healthy and is a key component in the upkeep of the insulating myelin sheath that coats our nerve cells.

It is also vital for red blood cell health, energy production and DNA replication and repair and has a role to play in breaking down the amino acid homocysteine, high levels of which have been linked to an increased risk of heart disease, stroke and dementia.

Which foods contain vitamin B12?

Vitamin B12 is found in animal produce including meat, fish, milk, cheese and eggs plus fortified foods such as some breakfast cereals and plant milks.

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Who is most at risk of vitamin B12 deficiency and why?

Certain people are more prone to having low B12 levels than others. These are:

Older people

Vitamin B12 deficiency is more common in older people, affecting around 1 in 20 aged from 65-74 and 1 in 10 over the age of 75.

As we age, our levels of stomach acid start to decline and these reduced levels can make it harder for B12 to be absorbed from food.

Vegans 

Research shows that vegans are at higher risk of vitamin B12 deficiency and the British Nutrition Foundation recommends they eat fortified foods as well as considering a B12 supplement to make up any shortfall. 

You can find out more about the vitamins and minerals that are harder to get from a plant-based diet in our guide to nutrient deficiencies vegans need to watch out for.

Medications that may impact B12 levels

• Proton pump inhibitors (PPIs). Used by nearly a quarter of adults globally, meds such as omeprazole are used to reduce stomach acid levels, but consistent use for 12 months or more can lower B12 absorption.
• H2-blockers. Also known as histamine H2-receptor antagonists (H2RAs), these are used to treat duodenal ulcers and gastric ulcers and can reduce circulating B12 concentrations with prolonged use.
• Anticonvulsants/anti-seizure medication. For example, phenobarbital, pregabalin, primidone and topiramate.
• Metformin. Used for type 2 diabetes, this is known to block B12 absorption and the MHRA (Medicines and Healthcare Products Regulatory Agency) suggests that the B12 levels of metformin users should be monitored if they develop deficiency symptoms.

If you are on any of these medications and think you have symptoms of B12 deficiency, speak to your pharmacist or GP for advice.

Coeliacs or other autoimmune condition sufferers

Some pre-existing health conditions, including autoimmune diseases like coeliac disease, autoimmune gastritis, thyroid disease and type 1 diabetes where the body's immune system attacks its own tissues, can increase B12 deficiency risk. 

Not to be confused with iron deficiency anaemia, where there aren't enough healthy red blood cells, pernicious anaemia is an autoimmune disease that prevents your body from absorbing B12 and is the most common cause of vitamin B12 deficiency in the UK.

Gastric surgery patients

People who've had bariatric surgery procedures have reduced B12 absorption and increased risk of deficiency.

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How to find out if you have low vitamin B12

It's important to see your GP if you have concerns. You should be able to access a test for free on the NHS if you qualify for NHS care. Your GP can check for B12 deficiency by carrying out a blood test and looking at your symptoms and medical history. 

NICE guidelines say you should be offered a test if you have at least one symptom or sign and one or more risk factors for the condition.

It is possible to buy a private vitamin B12 self-test, which will either be in the form of bloods being taken by a professional or as finger-prick blood sample to do yourself via post. These typically cost from around £35 upwards. 

However, we have concerns about self-test kits not giving the full picture, and it is generally best to talk to your GP first.

If you do opt for a self-test, make sure you check for the following:

• Check the test covers 'active B12' (the amount available for your body to use) rather than 'total B12' levels
• Check the blood testing laboratories used to test them are accredited by UKAS.
• A health professional will interpret / advise on the results.

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Vitamin B12 supplements

If you have any risk factors, it's worth aiming to include more B12-rich foods in your diet. But you may need supplements too, especially if you have one of the risk factors for deficiency and are diagnosed with low levels.

B12 injections and nasal sprays are available on prescription for those with diagnosed deficiencies, and oral supplements are also available to buy without prescription. 

Your GP or pharmacist can advise the best options for you depending on your needs.

Are B12 tablets, sprays or injections most effective?

When it comes to what type of supplement you should opt for, a 2024 systematic review and meta-analysis looked at oral, intramuscular and sublingual (e.g. under the tongue) supplements and found that they were all effective at increasing B12 levels without significant differences between them. However, what's best for you will depend on the reason you have a deficiency and should be decided with your GP.

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Where to buy vitamin B12 supplements

If you have a dietary deficiency the NHS Vitamin B12 guide says you should have 50-150mcg daily, or for a deficiency not caused by diet its one to two 1000mcg tablets once or twice a day. 

As B12 is a water-soluble vitamin, it's generally considered safe (because any not used will be excreted via your urine), but even so you shouldn't take more than the recommended doses unless recommended to do so by your GP, as some studies have shown possible negative impacts of overdoing it.

Over the counter B12 supplements come in strengths from 10-1200mcg daily. Higher doses and more palatable formulations, such as sprays, are typically pricier.

Here are the cheapest options we found:

Lower dose vitamin B12 tablets (10mcg)

• Vitamin Store Vitamin B12 (£2 for 180 tablets) at Savers and Wilko = 1p per daily dose
• Superdrug Energy vitamin B12 (£2.99 for 60 tablets, 5p per tablet, Superdrug) = 5p per daily dose
• Boots Vitamin B12 (£3.20 for 60 tablets, 5p per tablet, Boots) = 5p per daily dose

There is also a spray which gives 10mcg per two sprays (VitSpritz vitamin B12 oral spray, £9.95 for 30ml, Sainsbury's) but it costs more per dose = 8.6p per daily dose

Higher dose vitamin B12 (1200mcg)

Many of these are spray formats:

• Better You B12 Boost oral spray 1200mcg (£9.90 for 25ml, Tesco) Four sprays gives 1200mcg of B12 = 20p per daily dose.

• One Nutrition Vitamin B12-Max oral spray 1200mcg (£13.30 for 30ml, Morrisons) Six sprays gives 1200mcg of B12 = 36p per daily dose.  

You can also opt for a combination B-complex supplement, which gives you a wider range of options and prices and includes other B-vitamins.

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Which? tips for buying B12 supplements

Tablets tend to be cheapest

Basic tablets are by far the cheapest, especially if they are generic rather than branded.

For example, you can get 100mcg vitamin B12 tablets for 5p each at a supermarket (£2.80 for 60, Sainsbury's) compared to a branded version from Solgar which, at 85p a tablet, makes them 17 times more expensive. 

Check dosage info to avoid being caught out

Check the levels of B12 included and how many tablets or sprays make up the recommended daily dose so that you're comparing like with like. For example, 60 tablets will only mean a month's supply if the guidance says to take two a day.

Sprays and drops are most expensive

You'll pay more for novel 'sublingual' formulations, including Solgar's vitamin B12 sublingual chewable 1000mcg 'nuggets' (£17 for 100, 17p per dose, Boots) which dissolve under the tongue.

Make the most of retailer deals

If you need to take B12 supplements regularly, look out for multi-buy offers which can bring the cost down. Many of the big retailers including Boots and Holland and Barrett run regular deals, but check against budget retailers which may be cheaper still.

There are also economies of scale so buying a bigger bottle of supplements will usually bring the cost down (though always check).

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