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Hello, you may have just been diagnosed with B12 deficiency or you may have had this condition for a while. Sometimes our doctors do not tell us all we need to understand, so please use this page as your 'crash course' in B12 deficiency.

Please remember, if you are undiagnosed DO NOT SUPPLEMENT BEFORE TESTING - This could skew results and make diagnosis difficult.

Let your doctor (and the lab) know if you have been taking multi-vitamins and B12 supplements and you still have symptoms. You still require testing. 

This page provides a step by step guide but for ease you can click on the pink headings in the contents below to jump to a particular point. 

If you are struggling to achieve a diagnosis and need personalised help please see the contact page for more information.


1. Make a note of your symptoms.

Click here to check your symptoms or click here to check your child's symptoms. We have recently developed a smart phone app to test your risk of B12 deficiency. 

(Please note that hypo-thyroidismhyper-thyroidism Pyroluria and coeliac disease have overlapping symptoms and can be co-existing conditions.) 

Click here to read about causes of B12 deficiency. 

Have you been exposed to toxic gas or moulds? Please see B12 the antidote page.

Note anything that relates to you. Your doctor may not understand that certain drugs including metformin and Omeprazole cause B12 deficiency. There are also many drugs which deplete folate

Please use this page which will help with writing to your doctor and this blog post for further help. 

There is a downloadable poster which demonstrates some of the conditions which can occur with low B12 or indeed may be misdiagnosed in place of B12 deficiency. You will find this on our Very useful Links page.

2. Ask your doctor to test serum B12, folate (B9), ferritin (iron storage), and a full blood count (FBC).
Although not routinely tested on the NHS, MMA (Methylmalonic acid) and Homocysteine (tHCY) are good indicators of B12 deficiency. 

The importance of testing ferritin and folate cannot be stressed enough, folate and B12 need each other and a healthy level of ferritin (iron stores) is essential. These should be fasting tests so ask for an early appointment.

Sometimes doctors are reluctant to carry out these tests, however they can be done privately via home test kits, through online labs or private hospitals. For more information on testing please click here.

3. Once your results are back it is very important to obtain a copy.

Unfortunately many of us are incorrectly told that our results are 'normal' when in fact this is not the case. You are legally entitled to copies of your results but some practices may charge.

4. Learn to interpret your test results.

If you are symptomatic your serum B12 level could still show as ‘within range’ this test is known to be inaccurate. Click here to see the NEQAS B12 alert which explains about 'false normal' results and warns not to delay treatment. “In the event of any discordance between clinical findings of B12 deficiency and a normal B12 laboratory result, then treatment should not be delayed".

It is important to understand that the B12 serum test records both active B12 which can be used by the body and inactive B12 which can't. The test may record as much as 80% of inactive B12 otherwise known as B12 analogues.

Read here from the NHS website -

'A particular drawback of testing vitamin B12 levels is that the current widely-used blood test only measures the total amount of vitamin B12 in your blood. This means it measures forms of vitamin B12 that are "active" and can be used by your body, as well as the "inactive" forms, which can't. If a significant amount of the vitamin B12 in your blood is "inactive", a blood test may show that you have normal B12 levels, even though your body cannot use much of it. There are some types of blood test that may help determine if the vitamin B12 in your blood can be used by your body, but these are not yet widely available.'

This Clinical Review from the BMJ on B12 deficiency states:

"There is no ideal test to define deficiency and therefore the clinical condition of patients is of the utmost importance."


"If the clinical features suggest deficiency then it is important to treat patients to avoid neurological impairment even if there may be discordance between the results and clinical features"

A 'normal' serum B12 level can indicate a Functional B12 deficiency,  this is a genetic  condition which your doctor should investigate;

'Some people can experience problems related to a vitamin B12 deficiency, despite appearing to have normal levels of vitamin B12 in their blood. This can occur due to a problem known as functional vitamin B12 deficiency - where there is a problem with the proteins that help transport vitamin B12 between cells. This results in neurological complications involving the spinal cord'.

'We describe a case of functional vitamin B12 deficiency where the repeated measurement of a serum B12 level within the normal range led to delay in the diagnosis of subacute combined degeneration of the spinal cord, and possibly permanent neurological damage as a result....'

Symptomatic patients may be suffering from B12 deficiency caused by parasites or infections such as SIBO, this can lead to misdiagnosis since serum B12 levels will often be within range despite a possible severe deficiency.

Please note that if you suffer psychiatric symptoms of B12 deficiency, they too are reversible with correct B12 treatment. Psychiatric symptoms can manifest at higher levels than the lower reference ranges of the B12 serum test. In these cases it would be entirely appropriate for your doctor to carry out a therapeutic trial of B12 injections to confirm a deficiency. Folate deficiency can also have a huge impact on your mental health.

An extremely high B12 level without supplementation requires investigation.

These particular test results from an FBC (Full blood count) are important in B12 deficiency:

  • Ferritin
  • Folate
  • Red cell folate
  • MCV
  • MCH
  • MCHC
  • RDW
  • WBC

Click here for information on optimum levels

It is important to remember that B12 deficiency cannot be ruled out in the absence of anaemia and / or high MCV. Click here for more information compiled by @b12unme.

5. If you have results which confirm a deficiency, do not accept cyanocobalamin tablets

...unless you know that your deficiency is due to a dietary lack of B12. Remember B12 is only available from animal products, fortified foods and supplements! 

Oral supplements may effect serum levels but may not repair damage, deterioration may continue undetected if the symptoms of the patient are ignored whilst blood levels are relied upon.
This case of SACD went undetected in a 22 year old who had been given oral supplements which had 'corrected' her serum level.

This BMJ article discusses how ineffective oral B12 is, stating; '......a minority of patients respond clinically to oral therapy'.

A deficiency, even if caused through a vegan or vegetarian diet, should still be treated by injections in the first instance, in order to build levels fast.

See the new haematological guidelines.

Urge your family members to check the symptoms and causes page too, this deficiency could also be affecting your loved ones.

6. You should be given loading doses by injection. (six injections over two weeks)

If you have neurological symptoms then your doctor must treat you as per NICE and BNF guidelines, these both state that you must stay on loading dose frequency (every other day injections) until symptoms stop improving, see NICE Guidelines here. (Page 17 is about treatment, if you are going to print.)

Many of us are severely affected neurologically, and will have to remain on intensive B12 treatment for life. There are many reasons why patients cannot cope on quarterly or even monthly injections. (Incidentally this frequency was arrived at through GP audits and not clinical evidence!

You may have to remind your doctor that there is no known toxicity of hydroxocobalamin and that it is used in huge quantities to treat cyanide poisoning.

Once treatment starts you may notice certain reactions (for example spots) during or soon after the loading doses. 

During early intensive B12 treatment potassium levels may fall, causing hypokalemia, so please increase your intake of potassium rich foods.

Many people are not treated adequately enough for B12 deficiency, hence the reason I started a petition which asks for us to be allowed to buy injectable B12 OTC in the UK. 

7. Your doctor should adhere to these guidelines but sometimes this doesn’t happen.

The BNF (British National Formulary) Guidelines (9.1.2.) state how Hydroxocobalamin should be administered and each practice has a copy of this book. If you register you can print the page to show your doctor if they are non compliant.

Nerve damage takes a long time to heal that is why there is no limit on the administration of B12 injections in those suffering neurological symptoms. Four injections per year will not heal nerve damage, they will keep you alive but deterioration will continue!

There is an NHS Constitution which may help UK residents to gain access to correct treatment, this sets out the rights of patients and pledges of the NHS.

Please use this page which will help with writing to your doctor

For more help with accessing correct treatment please read here.

8. Ask your doctor/nurse to teach you how to self inject.

This will save you and your practice time and money, if you have neurological symptoms you could be injecting every other day for months. Please click here for the NHS injection guide.

9. If you are B12 deficient and it is NOT due to a dietary lack of B12 or due to a parasite or other curable forms, you will require injections for life.

In these cases, ask your doctor to write this in your notes. Some patients experience a complete withdrawal of treatment when changing doctors. 

10. If your results show that you are low in folate (B9) this will require supplementation, Vitamin B12 and folate need each other!

Your serum level should be at the upper end of the range see here. Please note: folic acid is widely prescribed but it may be that you require supplementation of the forms of folate more recognisable to the body: please click here for more information on this.

11. If you are low in ferritin (iron storage) you will require supplementation.

Iron supplements come in tablet and liquid form and as an infusion. Your doctor should advise what is best for you here and monitor levels accordingly. Please see here.

Please note doctors do not routinely test for haemachromatosis (iron overload). My local lab has a reference range of 10 - 450, the optimum level here would be around 60 -100. To read more on folate and ferritin levels please click here.

12. A good B complex will be required alongside your injections.

All B vitamins work together but please note; Vitamin B6 can cause neuropathy if taken daily for long periods in high doses

Please note, the folate contained in B complexes and multivitamins is commonly folic acid and this may not be the best form for you. Please see point 10 above.

13. In some patients potassium levels can drop (hypokalemia) with frequent B12 injections. 

Low potassium can cause symptoms such as severe headaches, palpitations and dehydration. Your doctor should keep an eye on this and you can help yourself by eating potassium rich foods. Magnesium is also a crucial nutrient that many of us are deficient in. 

14. If you doctor feels that you are not B12 deficient based on ‘within range’ results you must push for further tests.

If you have neurological symptoms and a doctor who is non compliant you must assert yourself or take someone with you who can support you. This page has been useful to many patients - 'Writing to your doctor' and you can also access personalised help here.

Click here for more information on B12 testing
. This NEQAS link will help your doctor to understand the inaccuracy of the B12 serum test. 

15. Your ferritin and folate levels will require periodic monitoring.

Iron must be kept at an optimum level and not become too high.

It would be pertinent for your B12 level to be monitored in the beginning but only in order to confirm that you are able to metabolise your injections. This testing should not be used to stop your treatment.

Once B12 treatment has commenced your B12 levels may remain high but it is the symptoms which are the marker for your treatment not the number on a test result.

Do not let your doctor stop your injections, there is a mistaken belief that your levels are replete once above range. This is a common and distressing practice which many patients contend with.

It is advisable to monitor your symptoms, you can do this with pen and paper but it may be helpful to use our NHS approved App  

If you value this website, consider donating. Donations support the free information provided on and its blog, which help those with B12 deficiency world wide.

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