Signs & 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.

Vitamin B12 deficiency results in damage to the fatty tissue, myelin, surrounding the nerves. B12 deficiency is progressive and symptoms may take years to develop. But, correct and timely B12 treatment can mean reversal of all of your symptoms.

The symptoms listed are the most common that are reported as a result of B12 deficiency. These are taken from Could it be B12? with the kind permission of Sally Pacholok. Even if you only suffer from a handful of the symptoms below, particularly neurological symptoms, it is advisable to get yourself tested and educate yourself about this deficiency. On our case study page. you can see how different collections of symptoms show up differently for each person. 

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 think you’d benefit from personalised help, please see the Work with me page for more information on how you can gain a tailored advice.


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

  • Tinnitus (ringing in the ears)
  • Tremor (involuntary trembling – shaking)
  • Paresthesia – numbness, tingling and pain
  • Confusion / disorientation
  • Weakness of legs, arms, trunk
  • Impaired vibration and position sense (affected awareness of joint position when eyes are closed
  • 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 – erectile dysfunction 
  • Paralysis – inability to move all or part of your body
  • Impaired fine motor coordination – inability to perform a precise movement with fingers/toes/wrists etc.
  • Muscular spasticity – where the muscles stiffen and become rigid
  • Bladder or bowel incontinence 
  • Impaired pain perception- inability to feel pain normally. 
  • Night time cramping 
  • Disturbance in taste and smell
  • Optic atrophy – degeneration/damage of the eye.
  • Neuropsychiatric (Mental health)...

    • Confusion/disorientation
    • Psychosis  
    • Postnatal depression
    • Hallucinations
    • Memory loss
    • Delusion
    • Depression
    • Suicidal thoughts
    • Mania – abnormally elated mental state
    • Anxiety
    • Paranoia – unfounded or exaggerated distrust of others 
    • Irritability
    • Apathy – lack of feelings or emotions
    • Personality changes
    • Inappropriate sexual behaviour
    • Violent/aggressive behaviour
    • Schizophrenic symptoms
    • Sleep disturbances – disruption of sleep patterns outside of environmental factors
    • Insomnia – inability to sleep
    • Changes in taste, smell, vision, and sensory/motor function which can be mistaken for psychiatric problems

    Haematological signs and symptoms...

    • Anaemia – decrease in red cells or haemoglobin 
    • 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 – increase in heart rate when going from lying or sitting to standing
    • Palpitations – rapid or irregular beating of the heart
    • Occlusive vascular disorder – limited or blocked blood flow
    • 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 – obstruction of blood vessel in the lungs

    Female specific problems...

    Male specific problems...

    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 – intestinal parasite caused by Giardia
    • Pancreatitis, pancreatic exocrine insufficiency
    • Decreased stomach acid
    • Gastropareisis – chronic condition where the stomach cannot empty in the normal way
    • Helicobactor pylori infection – bacterial infection in the stomach 
    • SIBO – Small intestinal bacterial overgrowth 
    • Gastrectomy – bariatric surgery (surgical removal of the stomach – partial or complete)  
    • Ileal resection – removal of the last part of the small intestine (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 – weakened bones
    • Fractures 
    • Suppressed activity of osteoblasts (cells that build bone)
    • Symptoms mimicking Parkinson’s and MS (multiple sclerosis)
    • Nominal aphasia – difficulty recalling names or words
    • Radiculopathy – chronic pain disorder
    • Increased susceptibility to infections
    • Poor wound healing
    • Malnutrition
    • Seizure – fits
    • Enlarged spleen (splenomegaly)
    • Enlarged liver (hepatomegaly)
    • Skin hyper pigmentation or hypo pigmentation – lighter or darker patches on the skin
    • Poor antibody production following vaccines
    • MTHFR Gene mutation

    Signs & symptoms in infants and children...

    • If your child exhibits any of the following signs or symptoms, insist that your doctor tests for B12 deficiency make sure to get a copy of the results. Please see the Children’s page for more information.

    • Developmental delay or regression
    • Apathy – Irritability
    • Hypotonia (decreased muscle tone)
    • Weakness
    • Tremortrembling/shaking
    • Involuntary movements
    • Seizures (fits)
    • Ataxia (Neurological disorder affecting balance, coordination and speech)
    • Anorexia and other eating disorders
    • Failure to thrive
    • Poor weight gain
    • Poor head growth
    • Poor socialisation
    • Poor motor skills
    • Language delay
    • Speech problems
    • Lower IQ – Intellectual disability
    • Anaemia – decrease in red cells or haemoglobin 
    • Macrocytosis (large red blood cells) Note – need not be present!

    Red flags of B12 deficiency in infants, children and teenagers...

    If your child exhibits any of the following signs or symptoms, insist that your doctor tests for B12 deficiency make sure to get a copy of the results. Please see the Children’s page for more information.

        • Movement problems, including difficulty in walking or writing
        • Mental changes – irritability, altered mood, poor memory, “flat” emotional tone, autistic-like withdrawal
        • Vision problems/abnormalities
        • Slowed weight and height gain
        • Leg pains or other abnormal sensations
        • Fatigue
        • Loss of appetite
        • An abnormally small head circumference in infants or toddlers
        • Apathy, lethargy, or irritability
        • Involuntary movements, such as arm waving in infants or toddlers
        • Tics
        • Grey hairs / premature greying
        • Areas of hypo pigmented skin in a Caucasian child and/or vitiligo, or areas of hyper pigmented skin in a black or Asian child
        • A rooting reflex after eight months of age (this reflex is usually absent after six months of age)
        • A history of any surgery (including dental surgeries) involving nitrous oxide. This anaesthetic agent is often administered during dental work or surgeries such as insertion of ear tubes in children with chronic ear infections, can inactivate the body’s stores of B12 and cause severe neurological damage
        • Failure to thrive (poor appetite, poor growth and/or weight gain, general poor health)
        • Chronic constipation
        • A diagnosis of developmental delay, autism, cerebral palsy, Intellectual disability, or other neurological disorder
        • Severe food allergies or sensitivities
        • A diagnosis of coeliac disease or gluten enteropathy
        • A thyroid disorder or other autoimmune disorder
        • A history of stroke or a diagnosis of arteriosclerosis – thickening, hardening or loss of elasticity of the walls of blood vessels
        • A diagnosis of any psychiatric or behavioural disorder including ADHD
        • A diagnosis of Down’s Syndrome

    Co-existing conditions

    Please note: Folate and iron deficiency often go hand in hand with B12 deficiency so it is important to have your folate and Ferritin (iron storage) levels checked alongside B12. Hypo-thyroidism, hyper-thyroidism, coeliac disease and pyroluria manifest with similar symptoms, and are common co-existing conditions

    There is a downloadable poster (with hyperlinks to journals behind each image) 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 and others on our posters page. 

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