Has your brain been feeling ‘foggy’? Do you feel fatigued a lot for no particular reason? These symptoms, along with feeling weak and having pins and needles, are signs that you may have a B12 vitamin deficiency. Want to be sure? We don’t blame you!

Here’s some information about how to test your B12 levels and why it’s so important.

What happens when your vitamin B12 is low?

Low levels of vitamin B12 can be difficult to spot until it’s too late and you are dangerously lacking, and a surprisingly high percentage of people are deficient.

In the United Kingdom 6% of adults younger than 60 years have a vitamin B12 deficiency and that figure rises close to 20% of those older than 60.

Vitamin B12 also tends to drop in pregnancy, but usually return to normal levels after giving birth.¹

Your body needs vitamin B12 for the following functions:^2,3

Releasing energy from food
Producing red blood cells
Normal immune function
Maintaining healthy psychological function
Normal nervous system function
Cell division

When your body is low in vitamin B12, it can show in a variety of ways, including:⁴

Extreme fatigue
A lack of energy
Feeling weak
A sore and red ‘Foggy’ brain
Confusion
Problems with understanding, judgement and memory
Disturbed vision

What causes a B12 deficiency?

There are several factors that can contribute to a vitamin B12 deficiency, including:⁵

Pernicious anaemia

This is the most common cause of vitamin B12 deficiency in the UK.

Pernicious anaemia is an autoimmune condition – which means your body’s natural defence system is attacking healthy body cells. It affects the stomach, attacking the cells that help the body absorb vitamin B12.

The cause of pernicious anaemia is unknown, but it’s most common in women around 60 years old, those with a family history of this condition, or people with another autoimmune condition, like vitiligo or Addison’s disease.

Diet

People can develop a vitamin B12 deficiency by not getting enough from the food and drinks they consume.

A diet including fish, meat and dairy products normally provides an adequate amount of vitamin B12, but people who exclude some or all of these foods, like vegans. Also, a diet with these foods but poor nutrition may also cause deficiency.

It’s worth noting that vitamin B12 stores in the body can last for around 2-4 years without being replenished. This means that a dietary change can take place a long time before any deficiency occurs.

Some stomach conditions

Some conditions concerning the stomach or stomach operations can affect how our bodies absorb vitamin B12.

One example of this is a gastrectomy – a surgical procedure where some of the stomach is removed, which can then lower or prevent vitamin B12, thereby increasing your risk of developing a vitamin B12 deficiency.

Some medicines

Some medication types can decrease the amount of vitamin B12 in your body.

For example, a medicine sometimes used to treat indigestion called proton pump inhibitors (PPIs) can worsen a vitamin B12 deficiency. This is because they inhibit the production of stomach acid, which our bodies need to release vitamin B12 from the food we eat.

Functional vitamin B12 deficiency

Functional vitamin B12 deficiency occurs when people have vitamin B12 deficiency symptoms yet appear to have normal vitamin B12 levels in their blood.

This can happen if there’s a problem with proteins that help transport vitamin B12 between bodily cells, which results in neurological complications involving the spinal cord.

What is a vitamin B12 blood test?

If you went to your GP with a suspected low vitamin B12 level, a B12 deficiency, or pernicious anaemia (a condition where you are unable to absorb vitamin B12 from the foods you eat) one of the first things they would do is book you in for a blood test.⁶

These vitamin B12 deficiency tests check:

The level of vitamin B12 in your blood
Whether your red blood cells are larger than the norm
If you have a lower-than-normal level of haemoglobin – a substance that transports oxygen around the body

But nowadays, you don’t necessarily have to go straight to the doctor. In fact, you can do B12 home tests first – if that’s what you feel more comfortable with.

Why do I need a B12 blood test?

A blood test is essential, as this is the only way to check your vitamin B12 levels. However, thanks to modern technology, going to the GP isn’t your only option if you want to test your vitamin B12 levels as we’ve just mentioned, thanks to test-at-home kits. We’ll explain the benefits of both options below.

Home B12 test kit vs a blood test from your doctor

So, why you would want to test your vitamin B12 levels at home instead of the usual route? Well, first of all, you get to choose what sort of blood test you’re getting.

The NHS has stated that there is a bit of a flaw with the current way B12 is tested. The most widely used blood test only measures the total amount of vitamin B12 in your blood.

This means that it tests both the ‘active’ (can be used by your body) and the ‘inactive’ levels of vitamin B12 (can’t be used by your body).⁷

One problem with lumping active and inactive vitamin B12 levels into the same test result is that you may be showing ‘normal’ B12 levels, even if most of it is inactive and your body can’t use it.

When you can choose your own test, you choose a test that measures only the active B12 levels, so you get a better picture of your actual vitamin B12 status.

Top benefits of home vitamin B12 test kits include:

No doctor’s appointment necessary
Don’t need to book off work/use holiday
Do it whenever is best for you
Quick and easy
You have more choice over what is tested

However, it is important to keep in mind that these sorts of tests are no substitute for seeing your doctor, especially if you are experiencing symptoms, as these companies will not be able to diagnose, consult or provide any treatment.

But, if you just want to know for peace of mind or if you should be upping the vitamin B12 in your life, they can provide very useful.

How do home B12 blood tests work?

It depends on the brand, but generally a home test for B12 will work a little like this:

You order a test online or pick up a test kit from a store/clinic.
It will likely contain a finger prick and corresponding vial to collect blood from your finger so that it can be tested for vitamin B12.
You will have to send it to a lab/return address or arrange for somebody to collect it for you.
It will get tested (hopefully by an accredited laboratory), and the service provider should communicate your results to you.

Do home B12 blood tests work?

If you go with a reputable home blood test brand that sends out clear instructions, good kit, uses accredited laboratories to test your blood samples, and details/communicates your results clearly, then yes, they should work.

Obviously, you have to take ownership of following instructions correctly and completing ‘your part’ at home, as this is key!

How to choose a home B12 test at home kit:

As we touched on above, the most important things you need to consider when choosing an at-home testing kit for vitamin B12 include:

Check if they measure active B12 levels or total B12 levels - choose which you would prefer. Remember total vitamin B12 levels tests are not always suitable for diagnosing a deficiency.
Do they use accredited UKAS laboratories (or equivalent) to test your samples? You don’t want just any old lab testing your results, make sure they are the real deal.
Do they have doctors on hand to help interpret your results? Some aftercare is sometimes necessary, especially if you have confusing results, so check if they have a doctor on board to help if needed.
Do they have good reviews? Check their brand website and the reviews they have received to see what other people think of their service.

How to get the best results from a home B12 kit

Here are a few tips on how to get the best results from any home blood test kit:⁸

To accurately determine deficiency or low levels of vitamin B12 you must stop taking any vitamin B12 supplements a few weeks before your test. Ask your doctor about this if it is prescribed to you.
You should also avoid taking biotin supplements for at least 2 days before you test – again, check with your doctor if it’s prescribed to you.
Follow instructions accurately for your specific blood test kit.

Another great option is our Vitamin B12 Testing Kit, processed by London Medical Laboratories.

Key benefits:

An easy and affordable way to check if your vitamin B12 levels are normal or you are deficient
Simple finger-prick sample method, which is sent off and checked by London Medical Laboratories with a doctor’s interpretation
Results should arrive in the next working day
Suitable for vegans and vegetarians

How to keep your vitamin B12 levels healthy

If you do discover you have a vitamin B12 deficiency or low amounts in your body, you should always seek the advice of your GP, who can help you get to the root of the cause and advise treatment.

Vitamin B12 supplements are widely available if you worry that your diet or other lifestyle factors may eventually lead to depleted vitamin B12 levels.

Most multivitamins contain vitamin B12 too, and it doesn’t hurt to pre-empt any potential vitamin B12 issues by supplementing, especially if you don’t eat many B12-rich foods.

You can also easily increase the B12 in your body by eating some or all of the following:

Meat
Fish
Dairy
Some fortified mock meats
Some fortified plant milks
Some fortified breakfast cereals
Some fortified nutritional yeast

Click here for more advice on vitamin B12, what it does, and how to keep your levels up.

The final say

A vitamin B12 deficiency can severely impact your life, and could even be irreversible, so it’s important that you get tested if you start to experience symptoms
Vitamin B12 helps release energy from food, make red blood cells, support the immune system, and more
You usually find vitamin B12 in meat, fish, dairy and fortified milks / breakfast cereals / mock meats
Vegans, vegetarians, and people aged 60 and older are more at risk than others, so should be more vigilant
A blood test is usually used to check vitamin B12 levels, which you can get from your doctor or order to complete at home from private companies
Blood tests for vitamin B12 usually measure either ‘total’ or ‘active’ vitamin B12, with active tests proving more relevant and useful to find out how your body is using vitamin B12
If you opt for an at-home vitamin B12 test, make sure they are reputable and used professionally accredited laboratories to test your sample
Always consult your doctor if you suspect or discover you are deficient in vitamin B12, as they can help find the cause and the best treatment for you

Last updated: 10 January 2023

Disclaimer

The advice in this article is for information only and should not replace medical care. Please check with your GP or healthcare professional before trying any supplements, treatments or remedies. Food supplements must not be used as a substitute for a varied and balanced diet and a healthy lifestyle.

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How to test your B12 levels

Summary

1What happens when your vitamin B12 is low?

2What causes a B12 deficiency?

3What is a vitamin B12 blood test?