The short answer
Vitamin B12 keeps your nerves and red blood cells healthy, and you can only get it from animal foods, fortified foods or supplements.1,7 Under 180 pg/mL, guidelines treat a shortage as confirmed.1
- A good result
- Over 350 pg/mL. Labcorp flags results under 232, but anything from 180 to 350 is a gray zone that can hide a shortage.1,7
- If yours is low
- It’s very treatable, with tablets or injections. Finding the cause matters too, such as your diet, an absorption problem or a medicine like metformin.1
- Should you test?
- Yes, if you have symptoms such as tiredness, pins and needles or memory problems, plus a risk factor such as a vegan diet, metformin, acid-reducers or stomach surgery.1
Check your result
Type the number from your report. It stays on this page.
- Low Under 180
- Borderline 180 to 350
- Normal 351 to 1,245
- High 1,246 or more
Enter your result to see what it means and what to do next.
Got a result from another lab? Ask Picardo about it. The app explains your results, and a physician can follow up.
Cutoffs from the 2024 UK guideline from NICE.1 Labcorp flags results under 232 and over 1,245.7 The bar isn’t to scale.
Low: you’re short of B12
Below 180, guidelines count B12 deficiency as confirmed.1 Left untreated, it can cause anemia and damage your nerves.1,7
Very treatable, but don’t leave it. See a clinician in the next few weeks, and within days if you have numbness, tingling or trouble with balance or walking. Those shouldn’t wait for more tests.1
- 1 Ask about treatment. Tablets work for many causes; injections are used when your gut can’t absorb B12.1
- 2 Find the cause. Ask whether to test for autoimmune gastritis (pernicious anemia), where your immune system stops your stomach absorbing B12.1
- 3 Check your blood count for anemia.1
Borderline: a second test can tell
Results here can go either way. Labcorp flags anything under 232 as low, but guidelines call the whole range from 180 to 350 indeterminate: some people in it are short of B12 and some aren’t.1,7 A second test, methylmalonic acid (MMA), rises when your cells lack B12, and is the most specific check.1,2 If you’re Black, your normal range may run higher, so a result here may matter more.1
Not urgent. It matters most if you have symptoms.
- 1 If you have symptoms, such as tiredness, numbness or memory problems, ask about an MMA test.1
- 2 Without symptoms, guidelines don’t suggest treatment. Get checked again if symptoms start.1
- 3 If you’re pregnant or breastfeeding, have autoimmune gastritis or have had stomach or bowel surgery, ask about treating it anyway. With anemia or balance problems, ask about starting treatment now.1
Normal
A B12 shortage is unlikely at this level.1
Nothing to worry about.
- 1 If you take B12, it may be lifting this number. Supplements can raise a result without fully fixing a shortage.1
- 2 If you use nitrous oxide, this test can look normal even when you’re short. Ask for MMA or homocysteine instead.1
- 3 If you have symptoms, look for other causes. If they last 3 to 6 months, guidelines suggest testing again.1
Higher than the lab range
B12 tablets and injections raise your level.1 If you don’t take any, a high level is worth looking into, because liver disease and some blood disorders can raise it.7
Not urgent. If you take B12, it’s expected.
- 1 If you take B12 for a shortage, carry on as your clinician advised.
- 2 If you don’t take B12, ask a clinician about checking your liver and blood count.7
What is a normal vitamin B12 level?
Labcorp’s range is 232 to 1,245 pg/mL.7 But B12 tests vary from lab to lab, and many low results turn out to be false alarms.2 So rather than one cutoff, the UK’s NICE guideline uses a gray zone:1
Low: you’re short of B12
Below 180, guidelines count B12 deficiency as confirmed.1 Left untreated, it can cause anemia and damage your nerves.1,7
Very treatable, but don’t leave it. See a clinician in the next few weeks, and within days if you have numbness, tingling or trouble with balance or walking. Those shouldn’t wait for more tests.1
Borderline: a second test can tell
Results here can go either way. Labcorp flags anything under 232 as low, but guidelines call the whole range from 180 to 350 indeterminate: some people in it are short of B12 and some aren’t.1,7 A second test, methylmalonic acid (MMA), rises when your cells lack B12, and is the most specific check.1,2 If you’re Black, your normal range may run higher, so a result here may matter more.1
Not urgent. It matters most if you have symptoms.
- 1 If you have symptoms, such as tiredness, numbness or memory problems, ask about an MMA test.1
- 2 Without symptoms, guidelines don’t suggest treatment. Get checked again if symptoms start.1
- 3 If you’re pregnant or breastfeeding, have autoimmune gastritis or have had stomach or bowel surgery, ask about treating it anyway. With anemia or balance problems, ask about starting treatment now.1
Normal
A B12 shortage is unlikely at this level.1
Nothing to worry about.
- 1 If you take B12, it may be lifting this number. Supplements can raise a result without fully fixing a shortage.1
- 2 If you use nitrous oxide, this test can look normal even when you’re short. Ask for MMA or homocysteine instead.1
- 3 If you have symptoms, look for other causes. If they last 3 to 6 months, guidelines suggest testing again.1
Higher than the lab range
B12 tablets and injections raise your level.1 If you don’t take any, a high level is worth looking into, because liver disease and some blood disorders can raise it.7
Not urgent. If you take B12, it’s expected.
- 1 If you take B12 for a shortage, carry on as your clinician advised.
- 2 If you don’t take B12, ask a clinician about checking your liver and blood count.7
What is vitamin B12?
Think of B12 as a package that needs an escort. Your stomach makes a protein, intrinsic factor, that carries B12 from your food into your blood. If the escort goes missing, you can run short however well you eat.
Your body needs B12 to make red blood cells and to keep the coating on your nerves healthy. Your liver stores it and recycles it carefully, which is why a shortage usually builds slowly.7
When B12 runs low, your bone marrow makes fewer, larger red blood cells, and nerves can start to misfire.7
What causes low B12?
- A diet with little or no meat, fish, eggs or dairy, such as a vegan diet without fortified foods or a supplement1
- Autoimmune gastritis, also called pernicious anemia, where your immune system stops your stomach absorbing B121
- Metformin, the diabetes medicine, over years3,4
- Acid-reducers taken for 2 years or more, such as omeprazole or famotidine5
- Stomach or bowel surgery, including many weight-loss operations, and celiac disease1
- Inhaling nitrous oxide (“laughing gas” or whippets) as a drug, which inactivates B121,8
- Some other medicines, including colchicine and the seizure medicines phenobarbital, primidone and topiramate1
What are the symptoms of low B12?
Symptoms creep up slowly, and you can have them without anemia:1
- Tiredness that has no other explanation
- Trouble concentrating or remembering (“brain fog”)
- Pins and needles, numbness or problems with balance and walking
- A sore, red tongue
- Low mood or anxiety
- Anemia, or large red blood cells, on a blood count
Does metformin lower B12?
Yes, slowly. In the Diabetes Prevention Program, 19.1% of people on metformin had low or borderline B12 after 5 years, against 9.5% on a placebo. The odds rose with every year of use.4
US diabetes guidelines suggest checking B12 from time to time on long-term metformin, especially with anemia or nerve symptoms, and yearly after more than 4 years.3 If yours is low, the usual fix is B12 alongside the medicine, with a review of whether you still need it.1
Acid-reducers are linked to low B12 too. In a study of over 200,000 people, 2 years or more of proton pump inhibitors, such as omeprazole, went with 65% higher odds of B12 deficiency, and H2 blockers, such as famotidine, with 25% higher odds. That’s an association, not proof that the drugs caused it.5
How to raise vitamin B12
- B12 tablets
At least 1 mg a day works for many causes, including some absorption problems.1 In small trials, tablets raised levels about as well as injections.6
- How much it helps
- A lot
- How sure we are
- Fairly sure
- B12 injections
Needed for life if autoimmune gastritis is the cause, or after your stomach or the end of your small bowel has been removed.1
- How much it helps
- A lot
- How sure we are
- Very sure
- More B12 in your food
Meat, eggs and milk contain it.7 If you eat little or none, fortified foods or a supplement fill the gap.1
- How much it helps
- Some
- How sure we are
- Fairly sure
- Stopping nitrous oxide
Inhaling it as a recreational drug inactivates B12, and stopping is part of treatment.1,8
- How much it helps
- A lot
- How sure we are
- Very sure
Don’t retest while you’re having injections. The number won’t show how well treatment is working, so clinicians judge progress by your symptoms instead.1
Which B12 test do you need?
Total B12, the test on this page, is the usual first test. When it’s borderline, a second test helps:
| Test | What it shows | When it’s used |
|---|---|---|
| Total B12 | All the B12 in your blood | The usual first test |
| Methylmalonic acid (MMA) | Whether your cells are short of B12 | To settle a borderline result, and as a first test after nitrous oxide use |
| Active B12 (holotranscobalamin) | The share of B12 your cells can take up | The preferred first test in pregnancy |
| Homocysteine | Rises when B12 or folate runs low | An alternative to MMA, including after nitrous oxide use. Low folate and kidney disease raise it too. |
Who should get a B12 test?
Guidelines suggest testing if you have at least one symptom and at least one risk factor:1
- You eat a vegan diet, or little animal food.
- You’ve taken metformin or an acid-reducer for a long time.
- You’ve had stomach or bowel surgery, including weight-loss surgery.
- You have celiac disease, or an autoimmune condition such as thyroid disease or type 1 diabetes.
- A close relative has had B12 deficiency or an autoimmune condition.
- You’ve used nitrous oxide recreationally. Ask for MMA or homocysteine, which can show a shortage that total B12 misses.1
Without symptoms, a borderline result usually doesn’t need treatment.1
How to get a vitamin B12 test, and what it costs
A vitamin B12 test costs $5.00 through Picardo.
- Results in 2 to 3 days, in the app
- Physician follow-up if you want one
- Free Labcorp draw, or $75 at home
- No other fees. HSA and FSA eligible.
It’s also part of the Base Core Annual – Men, Base Core Annual – Women, Heart Health, Brain Health Screening, Postpartum and Celiac / GI panels, if you’d rather test more at once.
Already have a result? Ask Picardo about itQuestions people ask
Can you have low B12 with a normal blood count?
Yes. Low B12 can affect your nerves, memory and mood before it causes anemia, so a normal blood count doesn’t rule it out.1
Are B12 tablets as good as injections?
For many people, yes. In small trials, high-dose tablets raised B12 about as well as injections, though the evidence is low in certainty.6 Injections are still the rule when your stomach can’t absorb B12, as with autoimmune gastritis or after stomach removal.1
Should I stop B12 supplements before the test?
Test before you start them if you can, and tell whoever orders the test if you already take B12. It can raise the number without fully fixing a shortage.1 Stop biotin, common in hair and nail supplements, for 3 days before, because it can upset the test.7
How long does B12 treatment take to work?
Symptoms can start to improve within 2 weeks, but it may take up to 3 months, and longer for them to clear completely.1
Often checked alongside
Test details
Sources
- 1 National Institute for Health and Care Excellence. Vitamin B12 deficiency in over 16s: diagnosis and management. NICE guideline NG239. London: NICE; 2024. Updated December 2024. www.nice.org.uk/guidance/ng239
- 2 Guéant JL, Alpers DH, Allen LH, et al. Expert perspectives on diagnosis and management of vitamin B12 deficiency in adults. Adv Nutr. 2026;17(10):100726. doi.org/10.1016/j.advnut.2026.100726
- 3 American Diabetes Association Professional Practice Committee for Diabetes. 3. Prevention or delay of diabetes and associated comorbidities: Standards of Care in Diabetes—2026. Diabetes Care. 2026;49(Suppl 1):S50–S60. doi.org/10.2337/dc26-S003
- 4 Aroda VR, Edelstein SL, Goldberg RB, et al. Long-term metformin use and vitamin B12 deficiency in the Diabetes Prevention Program Outcomes Study. J Clin Endocrinol Metab. 2016;101(4):1754–1761. doi.org/10.1210/jc.2015-3754
- 5 Lam JR, Schneider JL, Zhao W, Corley DA. Proton pump inhibitor and histamine 2 receptor antagonist use and vitamin B12 deficiency. JAMA. 2013;310(22):2435–2442. doi.org/10.1001/jama.2013.280490
- 6 Wang H, Li L, Qin LL, et al. Oral vitamin B12 versus intramuscular vitamin B12 for vitamin B12 deficiency. Cochrane Database Syst Rev. 2018;3(3):CD004655. doi.org/10.1002/14651858.CD004655.pub3
- 7 Labcorp. Vitamin B12, test 001503. Labcorp test menu. Accessed October 28, 2026. www.labcorp.com/tests/001503/vitamin-b12
- 8 U.S. Food and Drug Administration. FDA advises consumers not to inhale nitrous oxide products. Updated June 4, 2025. www.fda.gov/food/alerts-advisories-safety-information/fda-advises-consumers-not-inhale-nitrous-oxide-products
Updated 28 Oct 2026.
This is general health information, not medical advice: talk to your clinician about your results and before changing any treatment.