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Vitamin B12 Blood Test

Updated on December 5, 2021
Medically Reviewed by
Dr. Dhingra
Written by
Kelly Jamrozy
7 sources cited
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Vitamin B12, also called cobalamin, is a very important B vitamin. It plays a major role in the health of nerve tissues and brain functions. 

Additionally, vitamin B12 works together with vitamin B9, also known as folic acid or folate. These two help each other in making red blood cells. Red blood cells are crucial for oxygen transport throughout the body and if deficient, can lead to heart and lung problems. 

Vitamin B12 and folate also produce S-adenosylmethionine (SAMe), a compound involved in mood regulation and immune function.

Vitamin B12 and folate also produce S-adenosylmethionine (SAMe), a compound involved in mood regulation and immune function.

Cobalamin deficiency is dangerous because it can lead to irreversible damage to the brain and nervous system. Inadequate levels of vitamin b12 are also linked to cognitive impairment, fatigue, memory loss, shortness of breath, loss of appetite, and impaired vision.

To ensure healthy Vitamin B12 levels in the body, a vitamin B12 blood test is very helpful.

How Much Vitamin B12 Does Your Body Need?

“Normal” vitamin B-12 levels vary depending on factors like age and sex. Pregnant and lactating women will also have different vitamin B12 needs. 

In the United States, the National Institutes of Health (NIH) has a Recommended Daily Allowance (RDA) of 2.4 micrograms of Vitamin B12 per day. 

There have been no toxic or harmful effects associated with excessive intake of vitamin B12. This is because vitamin B12 is water-soluble. It dissolves in water and goes through the bloodstream. The body excretes any unwanted or excess vitamin B12 through the urine.

In rare instances, usually only when someone has liver disease or myeloproliferative disorders, are vitamin B12 levels too high. Most people pass anything their body doesn't use through their urine.

Problems arise when the body fails to get enough vitamin B12.

If you have a vitamin B12 deficiency, it may be because of the following reasons:

  • Not eating enough foods high in vitamin B12 (usually only an issue for vegans or vegetarians)
  • Lack of the protein that helps your body absorb vitamin b12
  • Hyperthyroidism
  • Pregnancy

If you have only a mild vitamin B12 deficiency, dietary changes might be enough to resolve the problem.

To ensure a healthy vitamin B12 level, eat foods that are high in vitamin B12, which include:

  • Organ meat, especially liver and kidneys
  • Beef
  • Pork
  • Lamb
  • Poultry
  • Ham
  • Tuna
  • Haddock
  • Fortified cereals
  • Fortified nutritional yeast
  • Milk, yogurt, cheese, and other dairy products
  • Eggs

Symptoms of Vitamin B12 deficiency

If you're experiencing any of the following symptoms, it may be a sign that your body doesn't have enough vitamin B12.

  • A pale yellow hue to the skin 
  • Glossitis or inflammation of the tongue. The tongue may change color, swell in size and develop an unusual appearance on its surface.
  • Lethargy: a state of weariness that involves reduced mental capacity, energy, and motivation)
  • Feeling faint: a feeling of lightheadedness with the sensation that you may pass out without really losing consciousness.
  • Palpitations: a sensation that the heart is pounding, fluttering, racing, or skipping a beat. You may feel it in your throat, chest, or neck.
  • Weight loss and reduced appetite.

Why Would Your Doctor Order a Vitamin B12 Test?

If you're experiencing any of the following signs and symptoms, your doctor might order a vitamin B12 test.

This can happen before or after other issues are ruled out as causes.

  • Fatigue
  • Weight Loss
  • Numbness or Tingling
  • Irritability
  • Mood Changes
  • Depression
  • Skin Issues
  • Muscle Pain
  • Joint Pain
  • Brain Fog
  • Decline in cognitive function

It's also common to undergo a vitamin B12 test if your doctor suspects you have pernicious anemia. This occurs when your body isn't able to absorb vitamin b12 from the foods you eat. No matter how careful you are with your diet, it’s of no use to you if your body can't use what you are putting in it.

A vitamin B12 test is also ordered because the patient is exhibiting certain nervous system issues, such as tingling, numbness, weakness in the limbs, or is experiencing issues with balance.

Why Is It Important to Test Vitamin B12 Levels?

As many as 46% of adults aged 30 to 70 are deficient in vitamin B12 – that's a significant percentage. Healthcare team members and physicians have largely overlooked the problem for decades, and it is worrying because low levels cause several psychiatric and neurologic problems.

B12 deficiency has been primarily underplayed in healthcare and ignored in favor of more recognizable and costly diagnoses. This approach has led to malpractice and substandard care, which have cost many individuals their health and wasted billions in health care dollars. 

In addition to just not feeling your best, vitamin B-12 deficiency also put you at risk of:

  • Excessive bleeding
  • Lightheadedness
  • Fainting
  • Difficulty finding veins to draw blood
  • Hematoma (bruising)
  • Infection
  • Megaloblastic anemia (or macrocytic anemia)
  • Vitamin deficiency anemia
  • Low levels of methylmalonic acid

Does an At-Home Vitamin B12 Test Provide Reliable Results?

Yes. Reputable testing companies have an independent board-certified physician review your results and report those results back to you.

It's important to schedule an appointment with your doctor to review the results, especially if anything seems abnormal about them.

Even if your test results from an at-home vitamin B test fall within the normal range, you can use the information you've collected along the way to make healthier lifestyle choices.

As you age, it becomes a greater struggle to maintain healthy vitamin and nutrient levels. Monitoring your levels is a great first step toward feeling your best throughout your life.

To reduce the health risks associated with low levels of vitamin B12, consider taking at-home vitamin B12 tests. EverlyWell’s B Vitamins test helps identify deficiencies in vitamins B6 (pyridoxine), B9 (folic acid/folate), and B12 (cobalamin). 

Pyridoxine deficiency causes mood changes, skin issues, neurologic problems, and frequent infections. Symptoms of folate deficiency include fatigue and mouth sores.

Using a blood sample, you get valuable insights into your body’s vitamin B levels and vitamin B needs. EverlyWell works with CLIA-certified laboratories that process your samples.  

Vitamin B12 Blood Test 2

EverlyWell - B12 Vitamin Test

EverlyWell’s B12 Test will tell you if your vitamin B levels are abnormal. It will then give you some steps you can take to get them back into balance.

Things to Consider Before Getting a Vitamin B12 Blood Test

You can have the test anytime.

There's no need for special preparations like fasting.

Your doctor may add it to the test that assesses your glucose and cholesterol levels. That said, you should always tell your physician about any supplements or medications you're taking before the test is administered.

When Should I See My Doctor About Vitamin B12 Levels?

Some people have inadequate vitamin B12 levels and don't even realize it. The signs tend to be subtle. They might not feel their best, but it's been so long since they were feeling optimal they don't recognize an issue.

Depending on your age and your overall health, it's a good idea to have vitamin levels tested periodically. If you are experiencing any of the symptoms listed above, you should speak to your doctor. If they don’t mention vitamin B12, bring it up and ask for the test. 

If you prefer not to go right to your doctor, try the at-home test and take the next step based on your results.

Treating Vitamin B12 deficiency

In most scenarios, vitamin B12 deficiency is quickly treated with intravenous medications or oral tablets that replace the missing vitamins.

The supplements are commonly administered by injection in the beginning. Then, based on whether your deficiency arises from your diet, you may need to swallow tablets between meals. These treatments may be necessary for the rest of your life.

In some situations, changing your diet will address the deficiency and prevent its reemergence. Assuming your body can process it, you can get vitamin B12 from fish, eggs, meat, yeast, and fortified foods.

If your physician chooses to give you injections, they'll likely use hydroxocobalamin, as it is the most dependable, particularly if you are suffering any neurologic symptoms. It is a better alternative to cyanocobalamin, as it offers better retention, greater availability, and it does not need declaration. Hydroxocobalamin does not cost more than cyanocobalamin, and it is readily accessible.


Vitamin B12 is crucial for proper bodily function, so you should have frequent blood tests to ensure you have enough.

If your test results report optimal levels, there's no need to do anything but eat a balanced diet. However, if your levels are low, you'll need to supplement your diet with injections or oral supplements.


  1. “Vitamin B12 Level: MedlinePlus Medical Encyclopedia.” Medlineplus.Gov,"
  2. "Vitamin B12." Oregon State University.
  3. "Vitamin B12." National Institutes of Health,
  4. "Folate (Folic Acid) - Vitamin B9" Harvard School of Public Health.
  5. Graells, J, Ojeda, RM et al. "Glossitis with linear lesions: An early sign of vitamin B12 deficienc." Journal of the American Academy of Dermatology, Volume 60, Issue 3, 2009, Pages 498-500, ISSN 0190-9622,
  6. "Vitamin B12 and Cognitive Function." Ontario Health Technology Assessment Series.
  7. Ramezanpour Ahangar E, Annamaraju P. Hydroxocobalamin. [Updated 2021 Jun 11]. In: StatPearls [Internet]. Treasure Island (FL): StatPearls Publishing; 2021 Jan-.
Dr. Dhingra
Dr. Harshi Dhingra
Medical Reviewer
Dr Harshi Dhingra is a licensed medical doctor with a specialization in Pathology. Dr. Dhingra has of over a decade in diagnostic, clinical, research and teaching work, including managing all sections of Pathology laboratory including histopathology, cytology, hematology and clinical Pathology.
Kelly Jamrozy
Content Contributor
Kelly has experience working with clients in a variety of industries, including legal, medical, marketing, and travel. Her goal is to share important information that people can use to make decisions about their health and the health of their loved ones. From choosing the best treatment programs to improving dental and vision health to finding the best method for helping anyone who is struggling with health issues, she hopes to share what she learns through informative content.
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