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Signs and symptoms

These lists of signs and symptoms below give you an idea of just how essential this vitamin is to all body systems. Our Apps can you help to monitor your symptoms and determine your risk.


When B12 deficiency attacks the nerves it takes many guises depending on the age and genetic vulnerabilities of the patient and the length and severity of the deficiency. B12 deficiency is progressive, signs and symptoms may take years to develop.

Please note: these signs and symptoms are THE most commonly reported, you might find that once B12 treatment begins, other symptoms may alleviate which are not listed here.

Whilst B12 deficiency may not always be the culprit (these signs and symptoms can stem from other causes) it is essential that your doctor rules this condition out due to the potential for misdiagnosis.

If you think you may be B12 deficient please head straight to the What to do next page. If you need personalised help please see the contact page for more information.

Folate and iron deficiency often go hand in hand with B12 deficiency. It is important to have folate and Ferritin (iron storage) levels checked alongside B12.

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.

You can view a 90 minute broadcast on B12 deficiency with me, from the Academy of Physical Medicine here. There is a small charge. 

On the case study page you will see how different collections of symptoms afflict each  person.

If you only suffer from a handful of the symptoms below, particularly neurological, it is advisable to get yourself tested and educate yourself about this deficiency.

Please note hypo-thyroidismhyper-thyroidismcoeliac disease and pyroluria manifest with similar symptoms, and are common co-existing conditions.


Neurological - Neurological symptoms must be treated with B12 injections every other day until the symptoms stop improving.

  • Tinnitus
  • Tremor
  • Paresthesia - numbness, tingling and pain
  • Confusion / disorientation
  • Weakness of legs, arms, trunk
  • Impaired vibration - position sense
  • Abnormal reflexes
  • Unsteady or abnormal gait / falls
  • Ataxia (Neurological disorder affecting balance, coordination and speech)
  • Balance problems
  • Difficulty walking
  • Dizziness
  • Restless legs
  • Visual disturbances / decreased-blurred vision / damage of optic nerve
  • Forgetfulness, memory loss
  • Dementia / intellectual deterioration
  • Impotence
  • Paralysis
  • Impaired fine motor coordination
  • Muscular spasticity
  • Bladder or bowel incontinence
  • Impaired pain perception
  • Nocturnal cramping
  • Disturbance in taste and smell
  • Optic atrophy


  • Confusion/disorientation
  • Psychosis
  • Post natal depression
  • Hallucinations
  • Memory loss
  • Delusion
  • Depression
  • Suicidal ideation
  • Mania
  • Anxiety
  • Paranoia
  • Irritability
  • Apathy
  • Personality changes
  • Inappropriate sexual behaviour
  • Violent/aggressive behaviour
  • Schizophrenic symptoms
  • Sleep disturbances
  • Insomnia
  • Changes in taste, smell, vision, and sensory/motor function which can be mistaken for psychiatric problems

Haematological signs and symptoms

  • Anaemia
  • Macrocytosis (large red blood cells)
  • Hyper segmented neutrophils
  • Generalised weakness, fatigue
  • Breathlessness
  • Pallor / jaundice
  • Chronic fatigue

Vascular Problems

  • Orthostatic hypotension/ Postural hypotension (low blood pressure when standing, which can cause fainting and falls)
  • Postural orthostatic tachycardia
  • palpitations
  • Occlusive vascular disorder
  • Transient ischemic attacks (TIAs, or 'mini stroke')
  • Cerebral vascular accident (CVA or 'stroke')
  • Myocardial infarction ('heart attack')
  • DVT - Deep vein thrombosis (blood clot to the leg or arm)
  • PE - Pulmonary embolism



Gastrointestinal - signs and risk factors

  • Loss of appetite/weight loss or anorexia
  • Epigastric pain (poor digestion, bloated feeling after eating small or normal sized meals)
  • IBS - Irritable bowel syndrome
  • Constipation
  • GERD - Gastric reflux disease - ulcers / mouth ulcers
  • Giardiasis
  • Pancreatitis, pancreatic exocrine insufficiency
  • Decreased stomach acid
  • Gastropareisis
  • Helicobactor pylori infection
  • SIBO Small intestinal bacterial overgrowth
  • Gastrectomy (partial or complete) - bariatric surgery
  • Illeal resection (partial or complete)
  • Malabsorption syndromes - Crohn's disease, coeliac disease etc)
  • Liver disease
  • Diphyllobothrium latum (fish tapeworm)

Additional Signs and Symptoms

  • Dry cracked corners of the mouth
  • Premature greying
  • Glossitis - swollen / sore tongue, geographic tongue
  • Fainting/light headedness
  • Osteoporosis
  • Fractures
  • Suppressed activity of osteoblasts (cells that build bone)
  • Symptoms mimicking Parkinson's and MS
  • Nominal aphasia - difficulty recalling names or words
  • Radiculopathy - chronic pain disorder
  • Increased susceptibility to infections
  • Poor wound healing
  • Malnutrition
  • Seizure
  • Enlarged spleen (splenomegaly)
  • Enlarged liver (hepatomegaly)
  • Skin hyper pigmentation or hypo pigmentation
  • Poor antibody production following vaccines
  • MTHFR Gene mutation

List Information provided with kind permission of Sally M. Pacholok R.N. & Dr. Jeffrey J. Stuart.

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