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Vitamin B12 Deficiency

Published: August 5, 2026Updated: August 20, 2026

Vitamin B12 deficiency is a condition in which the body lacks sufficient vitamin B12 to function properly. It is commonly caused by inadequate intake or absorption of the vitamin.

Quick summary

A deficiency in vitamin B12 can result in a wide range of symptoms affecting the nervous system, blood, and brain.

Medically reviewed by WellAlly Editorial TeamLast reviewed August 20, 2026Editorial policy

Key facts at a glance

ICD-10
E53.8, D50-D53
ICD-11
5A00.0
Body system
hematologic
Severity
moderate
Chronic
true

Risk factors

Factors that raise the chance of developing this condition. Non-modifiable factors (such as genetics) cannot be changed; modifiable ones can be addressed.

Vegetarian or vegan diet
Pernicious anemia
Gastrointestinal surgery or disease
Older age
Medications that affect stomach acid production

Complications

Problems that can arise from this condition or its treatment.

ComplicationSeverityFrequencyDetail
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When to seek medical help

Consult a healthcare provider if experiencing symptoms such as fatigue, weakness, or neurological issues.

Prevention

Steps that may lower risk, enable early detection, or reduce impact.

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Medication Comparisons

Compare medications used to treat Vitamin B12 Deficiency. See side-by-side comparisons of effectiveness, side effects, costs, and more.

View Medication Comparisons

Frequently asked questions

What are the symptoms of vitamin B12 deficiency?
Can vitamin B12 deficiency be prevented?
Are there any dietary sources of vitamin B12?
What is the recommended daily intake of vitamin B12?
Who is at risk for developing vitamin B12 deficiency?
  1. 1
    Mayo ClinicSource
  2. 2
    National Institutes of HealthSource
  3. 3
    World Health OrganizationSource

Click any link to access the full source. PubMed Central (PMC) links provide free full-text access.

This information is for educational purposes only and is not a substitute for professional medical advice, diagnosis, or treatment.

Medical Disclaimer

This content is for general informational and educational purposes only and is not a substitute for professional medical advice, diagnosis, or treatment. Always seek the guidance of a qualified healthcare provider with any questions you have about a medical condition, and never disregard professional medical advice or delay seeking it because of something you read here.

If you think you may have a medical emergency, call your local emergency number or go to the nearest emergency department immediately.

Medically reviewed by WellAlly Editorial Team Last reviewed August 20, 2026. · Read our editorial policy