Author: MAI Medical Information Team ·
Updated: 2026-04-15 ·
Reviewed by: Medical Information Team ·
Sources: WHO, UpToDate, PubMed
Vitamin B12 Deficiency: Symptoms, Normal Levels & Diagnosis
What Is Vitamin B12?
Vitamin B12 (cobalamin) is essential for nerve function, red blood cell production, and DNA synthesis. Your body cannot produce it — you must get it from food or supplements.
B12 Normal Ranges
| Level | Value (pmol/L) | Interpretation |
|---|---|---|
| Low | <148 | B12 deficiency — treatment needed |
| Borderline | 148–221 | Possible deficiency — monitor |
| Normal | 221–700 | Sufficient level |
Deficiency Symptoms
Common signs include fatigue and weakness, tingling in hands or feet (nerve damage), memory problems, pale or yellowish skin (megaloblastic anemia), and glossitis (tongue inflammation). Risk groups include vegans, people over 60, those with Crohn's disease or celiac disease, and long-term users of metformin or PPIs.
MAI Tip: Feeling fatigued or experiencing tingling? Check your B12 levels. Upload your blood test to MAI and find out if your level is sufficient.
⚠️ Important: This article is for informational purposes only and does not constitute medical advice.
Always consult your doctor before making health decisions.
Sources: World Health Organization (WHO), UpToDate Clinical Reference, PubMed Medical Research Database.
Sources: World Health Organization (WHO), UpToDate Clinical Reference, PubMed Medical Research Database.
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