Also Known As
Cobalamin Test, B12 Serum Test, Cyanocobalamin Test
What Is a Vitamin B12 Blood Test?
A Vitamin B12 blood test measures the level of cobalamin in your blood. B12 is an essential nutrient your body can’t produce on its own — it must come from food or supplements. It plays a critical role in red blood cell formation, neurological function, and DNA synthesis.
B12 deficiency is one of the most common and underdiagnosed nutritional deficiencies, particularly in older adults, vegetarians, vegans, and people taking certain medications. Because symptoms develop gradually and overlap with many other conditions — fatigue, brain fog, numbness — deficiency often goes undetected for years. A simple blood test is the only reliable way to know your B12 status.
What Does the Vitamin B12 Test Measure?
This test measures the concentration of Vitamin B12 (cobalamin) in your serum. B12 is stored primarily in the liver and is involved in:
- Red blood cell production — B12 deficiency causes megaloblastic anemia, where red blood cells become abnormally large and dysfunctional
- Nervous system health — B12 is essential for maintaining the myelin sheath that protects nerve fibers; deficiency can cause irreversible nerve damage
- DNA synthesis — every cell in your body requires B12 for proper replication
- Homocysteine regulation — low B12 elevates homocysteine, a marker associated with increased cardiovascular risk
Vitamin B12 Normal Range
| Level | Status | What It May Indicate |
|---|---|---|
| Below 200 pg/mL | Deficient | Supplementation or treatment needed |
| 200–300 pg/mL | Borderline low | May cause symptoms; retest or supplement |
| 300–900 pg/mL | Normal | Adequate B12 status |
| Above 900 pg/mL | Elevated | May indicate liver disease or certain blood disorders |
Reference ranges vary slightly by laboratory. Always review results with a qualified healthcare provider.
Note: Some people with levels in the “normal” range still experience B12 deficiency symptoms. If your level is below 400 pg/mL and you have symptoms, discuss further testing (MMA, homocysteine) with your provider.
Who Should Get a Vitamin B12 Blood Test?
High-risk groups who should test regularly:
- Vegans are also at elevated risk for low iron — consider pairing with a ferritin test for a complete nutritional picture.
- Adults over 50 — stomach acid production declines with age, reducing B12 absorption from food
- People taking metformin (diabetes medication) — long-term use depletes B12
- People taking proton pump inhibitors (PPIs) like omeprazole — reduce stomach acid needed for B12 absorption
- Anyone with Crohn’s disease, celiac disease, or other GI conditions affecting absorption
- People who have had gastric bypass or stomach surgery
- Pregnant or breastfeeding women — B12 needs increase significantly
Symptoms that warrant testing:
- Persistent fatigue or low energy
- Brain fog, difficulty concentrating, or memory issues
- Tingling or numbness in hands and feet
- Balance problems or difficulty walking
- Mood changes, depression, or irritability
- Inflamed or sore tongue (glossitis)
- Pale or yellowish skin
- Shortness of breath
If you’re experiencing several of these symptoms, a complete blood count (CBC) alongside your B12 test can help rule out anemia as a contributing cause.
Vitamin B12 Test Preparation
Fasting is preferred but not strictly required. For the most accurate baseline, avoid eating for 8 hours before your draw if possible. Do not stop taking B12 supplements before testing unless instructed — if you’re supplementing, your provider needs to know this when interpreting results, as supplements will raise your serum level even if tissue stores are depleted.
How Much Does a Vitamin B12 Blood Test Cost?
A Vitamin B12 blood test at Personalabs costs $81 — physician lab order included. No insurance required.
| Where You Get Tested | Typical Cost | Notes |
|---|---|---|
| Personalabs | $81 | Physician order included |
| Doctor’s office visit + lab | $150–$300+ | Office copay + separate lab bill |
| Hospital outpatient lab | $150–$350+ | Facility fees apply |
| At-home finger-prick kit | $30–$60 | Less reliable than venous draw |
HSA and FSA eligible. Vitamin B12 testing qualifies as a reimbursable medical expense.
Where Can I Get a Vitamin B12 Blood Test Near Me?
After ordering online, visit any of our 4,000+ partner patient service centers nationwide — at Labcorp locations.
Step 1: Order online — your physician-approved lab order is ready within 2–4 hours. Step 2: Find a lab near you using our Lab Locator. Step 3: Walk in for your blood draw — no appointment needed at most locations. Step 4: Get results in your secure Personalabs account within 24–48 hours.
Frequently Asked Questions About the Vitamin B12 Blood Test
Can I order a Vitamin B12 blood test without a doctor?
Yes — in most states. Personalabs provides a physician-approved lab order with your purchase. No referral needed. Our network physician approves your order within 2–4 hours. A small number of states restrict direct-to-consumer lab testing; contact us to confirm availability in your state.
What is a normal Vitamin B12 level?
Most labs consider 300–900 pg/mL to be normal for adults. Levels below 200 pg/mL are considered deficient. Many functional medicine providers target 400–700 pg/mL as optimal. Levels below 300 pg/mL with symptoms may still warrant treatment even if technically “normal” by standard ranges.
Do I need to fast before a Vitamin B12 blood test?
Fasting is preferred for the most accurate result, but not strictly required. If you’re testing alongside a lipid panel or CMP, the fasting requirement for those tests covers your B12 draw too.
What causes Vitamin B12 deficiency?
The most common causes are inadequate dietary intake (strict vegan or vegetarian diet), impaired absorption (low stomach acid, Crohn’s, celiac, gastric surgery), and medication interference (metformin, PPIs). Pernicious anemia — an autoimmune condition where the body can’t produce intrinsic factor needed for B12 absorption — is another significant cause, particularly in older adults.
Can B12 deficiency cause permanent damage?
Yes — if left untreated long enough. Neurological damage from B12 deficiency, including nerve damage causing tingling, numbness, and balance problems, can become permanent if the deficiency is severe and prolonged. This is why early detection matters. Anemia from B12 deficiency is reversible with treatment; nerve damage may only partially recover depending on how advanced it was.
What is the difference between a B12 test and a B12 and Folates test?
The standalone B12 test measures only cobalamin. The Vitamin B12 and Folates test adds folate (B9), which works closely with B12 in red blood cell production and DNA synthesis. Folate deficiency can mask B12 deficiency on a standard CBC, so testing both together gives a more complete picture — especially important for vegans, pregnant women, and people with anemia.
How long does it take to correct a B12 deficiency?
With supplementation or injections, serum B12 levels typically normalize within 4–8 weeks. However, neurological symptoms may take months to improve, and in severe cases may not fully resolve. Follow-up testing at 3 months confirms whether your levels have responded.
How long does it take to get Vitamin B12 blood test results?
Results are typically available in your Personalabs account within 24–48 hours of your blood draw.
