Add as bookmark

Vitamin B12 – Are You Deficient?

by Penny Crowther(more info)

listed in nutrition, originally published in issue 239 - July 2017

Severe B12 deficiency is known to cause pernicious anaemia, an illness which has clearly diagnosable symptoms.  However, there are a plethora of other symptoms which can be related to a milder shortage of B12 which often go unrecognised by GPs. Recently there has been more recognition amongst specialists that B12 deficiency can be responsible for more wide ranging symptoms, that it is a much more common issue than was previously thought and that it is very under diagnosed. 

Testing for B12 Deficiency

One of the major reasons for missing B12 deficiency is that the traditional serum test for B12 is wholly inadequate. The accepted reference range for ‘normal’ levels is very wide (180-1000pmol/ml) and most GPs won’t consider you have a deficiency unless you are outside this range. This policy may change as a recent paper in the British Journal of Haematology concluded that the reference range is inadequate and that patients should be treated with B12 if they have strong signs of deficiency, regardless of whether their B12 levels fall within the accepted parameters. It also suggested that patients whose B12 levels are in the lower half of ‘normal levels’ may in fact be deficient.  The paper mentions the value of testing serum holotranscobalamin, the active form of B12. Current testing of total B12 includes both the active and inactive (bound and unusable) forms of B12.

A further problem is that ‘normal’ levels of B12 vary from person to person. So, one individual can have low levels according to the reference values but be symptom-free and another individual can have ‘normal’ levels but have symptoms.  This points to the existence of different optimal levels for each person and means the individual symptom picture is probably more important than the reference values. Blood samples will be influenced by recent food intake too. So if a meal high in B12 has been consumed prior to the blood test this will skew results.

Crowther 239 Vitamin B12

Common Reasons for being Vitamin B12 Deficient

Testing aside, another major factor which makes B12 deficiency more common is that this vitamin suffers from problems with absorption, even though the average diet typically supplies enough. Vegan and vegetarian diets are more vulnerable to deficiency of B12 due to the fact that the best sources of this vitamin are animal derived foods. However there are vegetarians and vegans who are not B12 deficient which suggests that absorption of this vitamin is just as important a factor as dietary intake.

Vitamin B12 is unique amongst vitamins in that it needs a protein substance called Intrinsic Factor (IF) made by cells in the stomach, in order to be used by the body.  Chronic inflammatory conditions of the stomach lining mean that IF cannot be produced.  Inflammation can be caused by H pylori infection, advancing age or an autoimmune condition whereby the body attacks the stomach cells so that they cannot produce IF or destroys the IF itself (pernicious anaemia).

Even if Intrinsic Factor is normal, conditions affecting the small intestine will affect B12 absorption, such as Coeliac disease, Inflammatory bowel disease (such as Crohns or ulcerative colitis) or surgery that removes part of the small intestine such as gastric bypass for weight loss.

Another group of people vulnerable to B12 deficiency are those with dysbiosis, which is an overgrowth of unhealthy disease causing bacteria. Small intestine bacterial overgrowth (SIBO) is now a recognized condition by gastroenterologists.  Low stomach acid (hypochlorhydria) which becomes much more common as we age, is a significant contributing factor to dysbiosis.

Other reasons for B12 deficiency are heavy alcohol consumption and prolonged stress. Under stress, adrenaline is produced by the adrenal glands. This is part of the ‘fight or flight’ reaction and is meant to provide a short lived burst of energy to cope with a stressful situation.  In the case of chronic stress, demand on B vitamins such as B12 and B5 is greatly increased over a longer period. 

There are some commonly used medications which deplete vitamin B12. Proton pump inhibitors prescribed for stomach ulcers are the worst offenders. Stomach acid is vital for the breakdown of animal proteins containing vitamin B12. Metformin, a drug used to treat women with Polycystic ovary syndrome (PCOS) and diabetes also depletes B12 levels. The contraceptive pill may lower levels of B12 but studies are not conclusive.

How Will Deficiency of B12 Affect you?

Vitamin B12 affects the functioning of the brain and nervous system. It is needed for the conduction of nerve impulses and for the production of the protective myelin sheath around nerves.  It’s known that B12 deficiency becomes much more common in people over 60 (figures suggest 40% of this age group are affected).  It is interesting to note that symptoms of Alzheimer’s disease and those attributed to ageing in general such as cognitive decline, memory loss and dementia mimic those of B12 deficiency.  

B12  is also a key vitamin for energy as it is needed for making red blood cells. Red blood cells are produced regularly in the bone marrow and contain a substance called haemoglobin which carries oxygen all around the body. B12 (along with iron and folic acid) is essential for producing these red blood cells and haemoglobin. So, many deficiency signs of B12 are linked with anaemia, which is caused by the body producing reduced numbers of red blood cells or abnormally shaped red blood cells which carry less oxygen.

The most common symptoms of anaemia are extreme fatigue, lethargy, breathlessness, pale skin (sometimes with a yellow tinge due to fragile red blood cells leaking the yellow bile pigment, bilirubin), feeling faint, irregular heartbeat, headaches, sore tongue, mouth ulcers, loss of appetite and cold hands and feet.

Other symptoms associated with B12 deficiency are linked with the immune system and nervous system. For example;

  • Frequent infections;
  • Mouth ulcers;
  • Nerve problems such as a tingling sensation, numbness, pins and needles  (due to lack of oxygen to nervous system), muscle weakness, problems with balance;
  • Disturbed vision, blurred vision, double vision, light sensitivity;
  • Irritability, anxiety, depression (probably because B12 is needed to make neurotransmitters such as dopamine and serotonin);
  • Forgetfulness, absentmindedness, increased chance of getting psychosis and mania and dementia;
  • Weakness, tiredness, or light-headedness, dizziness.  

IBS symptoms, low blood pressure, a history of infertility and miscarriage, autism spectrum disorder, multiple sclerosis,  Graves’ disease and Lupus all warrant B12 investigation. 

Food Sources

Cheese, milk and yoghurt are the primary source of this vitamin, apart from meat or fish.  Eggs also contain B12. Fortified foods have some (for example, breakfast cereals) but these are often highly processed.


There is evidence that high dose oral supplements can be very effective. The Food Standards Agency recommend 2000 mcg (2mg) as the safe upper limit. When choosing a supplement make sure it contains B12 in the form of methylcobalamin, which is believed to be the most efficiently absorbed by the body.  More companies are making this form; however you will still have to search around as the most common form in usage is cyanocobalamin which is a synthetic form and cheap to produce. Hydroxycobalamin is fermented from bacteria and is second choice after methylcobalamin.

It’s also worth taking a probiotic to ensure a good balance of healthy flora.  Look for a high count of bacteria and the absence of  FOS (fructooligosaccharides) which can cause bloating in susceptible individuals.

Injections are available under prescription but after the initial booster they are only given once every 3 months and since B12 is water soluble, much of it is excreted within 24 hours. Some people find that their symptoms return long before the next injection is due.

Finally it is important to realize that all the above symptoms can related to issues other than B12 deficiency! Working with a GP and nutritional therapist is recommended.


Vinod Devalia et al. on behalf of the British Committee for Standards in Haematology. Guidelines for the diagnosis and treatment of cobalamin and folate disorders. June 2014.

Goodman M, Chen XH, Darwish D. Are U.S. lower normal B12 limits too low?. Journal of the American Geriatrics Society 44 (10): 1274–5. PMID 8856015. Oct 1996.

Mitsuyama Y, Kogoh H. Serum and cerebrospinal fluid vitamin B12 levels in demented patients with CH3-B12 treatment-preliminary study. The Japanese Journal of Psychiatry and Neurology 42 (1): 65–71. doi:10.1111/j.1440-1819.1988.tb01957.x.PMID 3398357. Mar 1988.


  1. No Article Comments available

Post Your Comments:

About Penny Crowther

Penny Crowther BANT CNHC qualified as a nutritional therapist in 1997 and has been in clinical practice ever since. She has seen several thousand clients over the years, at her practice in London and online. Penny now specializes in nutrition for women in their 40s and beyond, particularly around peri and post menopause. Mid Life for women can be a time when fluctuating hormones play havoc with your wellbeing. In the midst of all the publicity around HRT, it's easy to forget just how powerful diet and lifestyle changes can be when it comes to navigating the menopausal years.

Penny will guide and support you through specific changes to your diet, targeted to you specifically, in midlife. She provides practical, easy to follow menu plans with easy and delicious recipes. The food you eat affects every cell and system in your body. It optimizes how you look and feel, both mentally and physically.

To book an appointment view consultation options here >>

As well as being a regular columnist for Positive Health, Penny has written for Holland and Barrett, and contributed to articles for the Daily TelegraphThe Times Literary supplement, Pregnancy & Birth and Marie Claire. She has been featured in the Daily Express, Daily Mirror and on local radio.

Penny is a registered nutritional therapist with standards of training endorsed by BANT (British Association for Applied Nutrition and Nutritional Therapy) and CNHC. This includes completing 30 hours of continuing professional development, annually.

Penny’s approach to health is holistic, and takes into account emotional, mental and environmental factors as well as nutrition. She has trained in coaching and studied many complementary therapies before qualifying as a nutritionist, which provides a broad foundation of knowledge in her nutrition practice. Penny may be contacted on Tel: 07761 768 754;

  • Water for Health

    Specialist online health store focused on hydration, body pH balance and quality nutrition.

  • nutrition and cancer

    by Sandra Goodman PhD The latest scientific research regarding Nutrition and Cancer. Full details at

  • June Sayer Homeopathy

    Training Academy Homeopathy Nutrition Reiki, Distant Learning. Diet, Health Screening, Detox, Stress

  • Liposomal Nutrients

    Optimum system for nutrient delivery to cells - fully bioavailable vitamins absorbed and metabolised

  • mycology research MRL

    MRL markets mushroom products food grade US & Netherlands GMP standards. Health Professional Videos

  • College of Ayurveda UK

    Diploma in Āyurvedic Medicine, 4-year self-paced distant learning program in Āyurvedic medicine.

  • Seaweed as Superfood

    Comprehensive nutrient balance found in no other natural food but seaweed: colon health, weight loss

top of the page