Vitamin B12 · low result
What does a low Vitamin B12 mean?
Short answer
Low vitamin B12 causes fatigue, tingling, memory problems and eventually anemia, and it develops slowly — often from poor absorption rather than diet. Autoimmune pernicious anemia, metformin, long-term acid suppressants, gastric surgery, celiac disease and vegan diets are the common causes. Borderline results (roughly 200–300 pg/mL) can be functionally low; methylmalonic acid clarifies.
Medically reviewed by Youmna DiStefano, MD · Last reviewed September 2026
What is the normal range for Vitamin B12?
- age 18+: 200 – 1100 pg/mL
Common in vegetarians/vegans, older adults, and people on metformin or acid-suppressing medications. Can cause anemia and neurological symptoms.
Full reference table, citations and testing options: Vitamin B12 biomarker page.
What are the common causes of low Vitamin B12?
- Pernicious anemia (autoimmune loss of intrinsic factor)
- Metformin, proton-pump inhibitors and H2 blockers with long-term use
- Gastric bypass or other stomach surgery; atrophic gastritis in older adults
- Celiac disease, Crohn's, small-bowel overgrowth
- Vegan or strict vegetarian diet without supplementation
- Nitrous oxide exposure
What symptoms go with low Vitamin B12?
- Fatigue, weakness, pale skin
- Numbness or tingling in hands and feet, unsteady walking
- Memory problems, low mood, irritability
- Sore tongue, mouth ulcers
What do clinicians usually check next?
- Methylmalonic acid (and sometimes homocysteine) for borderline values
- CBC with MCV — macrocytosis supports deficiency
- Intrinsic factor antibodies when pernicious anemia is suspected
- Folate, since the two deficiencies travel together
Follow-up tests available at TestWell: CBC with Differential ($21.99), CBC (Complete Blood Count) ($21.99), Homocysteine ($27.99), Methylmalonic Acid (MMA) ($49.99), Folate (Vitamin B9) ($32.99).
How do you recheck Vitamin B12?
Prices are cash-pay; every order adds one $6 lab processing fee. Physician authorization is included; no insurance or referral needed.
| Test or panel | Type | Price | Fasting | Results |
|---|---|---|---|---|
| Basic Vitamin Deficiency Panel | Panel · 3 tests | $89.99 | No | 1–3 business days |
| Comprehensive B12 Deficiency Panel | Panel · 3 tests | $79.99 | Yes | 5–12 business days |
| Baseline Anemia Panel | Panel · 5 tests | $74.99 | Yes | 2–4 business days |
| Vitamin B12 | Test | $25.99 | No | 2–4 business days |
Common questions
Is a B12 of 250 low?
It's in the gray zone. Some people at that level have a true functional deficiency, which methylmalonic acid can reveal. Symptoms count — tingling or memory changes at 250 warrant follow-up.
How long does it take to fix low B12?
Blood levels rise within weeks of replacement; nerve symptoms can take months to improve and may not fully reverse if long-standing, which is why early detection matters.
Sources
Educational content, not a diagnosis. Lab results are one input; a clinician interprets them with your history and exam.