Vitamin B12 Deficiency
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.
A deficiency in vitamin B12 can result in a wide range of symptoms affecting the nervous system, blood, and brain.
Key facts at a glance
- ICD-10
- E53.8, D50-D53
- ICD-11
- 5A00.0
- Body system
- hematologic
- Severity
- moderate
- Chronic
- true
Signs and symptoms
Common signs and symptoms that may indicate this condition.
Fatigue
(hematologic)Generalized symptoms
(hematologic)Noticeable symptoms that may vary in intensity over time.
Frequency: Common at all stages
Pallor
(hematologic)Paresthesias
(hematologic)Glossitis
(hematologic)Diagnosis and tests
How this condition is diagnosed and what test results mean.
Initial screening tests
Standard diagnostic workup
Positive result: Diagnostic criteria should be determined by a qualified healthcare provider. [Content pending medical review.]
Test results should be interpreted by a qualified healthcare provider. [Content pending medical review.]
Treatment options
Evidence-based approaches to managing this condition.
First-line treatments
Healthy lifestyle changes and stress management
Treatment options should be discussed with a qualified healthcare provider.
Parenteral Vitamin B12 Replacement
Intramuscular or subcutaneous cyanocobalamin or hydroxocobalamin bypasses absorption defects to rapidly replenish depleted B12 stores and correct hematological manifestations.
B12-Rich Dietary Sources
Increasing intake of animal products including meat, fish, eggs, and dairy provides bioavailable B12; fortified cereals offer alternatives for plant-based diets.
Additional treatment options
High-Dose Oral B12 Supplementation
Oral methylcobalamin or cyanocobalamin at pharmacological doses (1-2mg daily) can overcome absorption limitations through passive diffusion when intrinsic factor deficiency is present.
complementaryRegular B12 and Methylmalonic Acid Monitoring
Serial measurement of serum B12 and methylmalonic acid levels confirms treatment adequacy and guides maintenance dosing frequency to prevent both under- and over-treatment.
monitoringVegetarian/Vegan Dietary Planning
Structured meal planning with adequate B12-fortified foods and discussion of supplementation needs prevents deficiency in those following plant-based diets.
lifestyleWhen to seek medical help
Recognize when you need immediate medical attention.
Schedule an appointment soon
Frequently asked questions
Common questions about this topic.
What is Vitamin B12 Deficiency?
Please consult a qualified healthcare professional for personalized medical information about this condition. [Content pending medical review.]
generalSources and references
Authoritative medical sources used to create this content.
Langan RC, Zawistoski KJ. Update on vitamin B12 deficiency. Am Fam Physician. 2021.
Green R, Allen LH, Bjorke-Monsen AL, et al. Vitamin B12 deficiency. Nat Rev Dis Primers. 2017.
Wang H, Li L, Zhang Y. Efficacy of oral versus intramuscular vitamin B12 supplementation: a systematic review and meta-analysis. J Clin Endocrinol Metab. 2020.
Gironde C, Rigal A, Cougoul A. Oral cobalamin treatment in patients with food-cobalamin malabsorption: a prospective study. Blood. 2019.
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.
Complications
Problems that can arise from this condition or its treatment.
| Complication | Severity | Frequency | Detail |
|---|---|---|---|
| — | — | — | |
| — | — | — | |
| — | — | — | |
| — | — | — | |
| — | — | — |
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 ComparisonsFrequently 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?
Sources
- 1Mayo ClinicSource
- 2National Institutes of HealthSource
- 3World 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.
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