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Vitamin B12 Testing and Supplementation: The Nuances of a Common Test

Testing for vitamin B12 deficiencies should include a vitamin B12 level and a methylmalonic acid level run at the same time. Lab reference ranges quoted for vitamin B12 are frequently insufficient, serum B12 levels should be at least greater than 300pg/mL for good neurological health. Vitamin B12 is found naturally in animal proteins, and in some fortified vegan foods. Oral B12 supplementation has been shown to be as effective as B12 injections, with lower cost and greater convenience.

Woman sorting blood testing vials

I frequently conduct tests to measure vitamin B12 levels, particularly among patients grappling with general fatigue, as highlighted in my previous blog post titled "Busting Fatigue: The Essential Role of Vitamin B12." Additionally, I administer these tests for patients who have manifested particular neurological impairments. However, the process of vitamin B12 testing is far from straightforward; there are some nuances that require some understanding. Stick with me here while we explore lab testing for vitamin B12 and how to supplement correctly. It may make the difference between feeling just okay and experiencing a remarkable sense of well-being!

How Do We Test for Vitamin B12 deficiency?

I consistently conduct two laboratory tests simultaneously to assess the potential need for vitamin B12 supplementation. These tests involve analyzing blood samples for both vitamin B12 levels and methylmalonic acid blood levels. Utilizing the methylmalonic acid test adds greater sensitivity compared to a sole vitamin B12 blood test. Performing both tests in conjunction provides a comprehensive evaluation of an individual's vitamin B12 status. It's important to note that while a vitamin B12 blood test might show results within the normal range, an elevated methylmalonic acid level could still suggest a deficiency in certain cases, and this is why we need to look at both values.

Woman working in a chemistry laboratory

What Do My Vitamin B12 Lab Numbers Mean?

Curiously, because vitamin B12 is used by the body for more than one purpose, there are different minimum requirements depending on what you are focusing on. It is the only vitamin that I routinely check where the reference range given by the lab is not always meaningful in clinical practice. If you do a regular Google search on what a normal blood B12 level should be you may get an answer like “A normal serum B12 level typically falls within the range of 200 to 900 picograms per milliliter (pg/mL) or 148 to 664 picomoles per liter (pmol/L).” BUT this is not accurate for two reasons:

  1. There is a difference between minimums for blood disorders and for neurological disorders and

  2. It's important to note that the "normal" range can vary slightly depending on the laboratory and the reference values they use. When you do vitamin B12 testing you will have to look at your specific lab normal reference ranges.

Due to the above 2 points, I will talk broadly speaking here. Generally, the levels indicating deficiency for blood disorders are lower than those indicating deficiency for neurological disorders. The lab that I use reports a deficiency when levels drop below 189 pg/mL which is true for blood disorders, BUT… levels below 300pg/mL are not conducive to good nerve health and can indicate a deficiency from a neurological perspective. Why the reference range at my lab does not take neurological health into account I do not know, but that is just the way it is reported, and many labs do this with their B12 reports. So I always suggest to my patients that we shoot for levels above 300 pg/mL IF we also have a normal methylmalonic acid level. If I don’t know the methylmalonic acid level then I will just shoot for above 500pg/mL. Please recognize that not knowing methylmalonic acid level results in a very large brush stroke, and not the most accurate way to do things, but it can work.

How Much B12 Should I Be Eating?

The recommended daily allowance of vitamin B12 for the average person varies based on factors such as age, gender, and individual health conditions. Generally, adults require around 2.4 micrograms (mcg) of B12 per day. However, specific needs may differ. For individuals over the age of 50, the ability to absorb B12 from food decreases, and therefore, a higher intake is often recommended.

Steak dinner

Foods Rich in Vitamin B12:

I find the following list of B12-rich foods quite fascinating, let me share some insights that might surprise you. For example, did you know that a cup of yogurt actually contains more B12 than 100g of cooked chicken? It's not something that might immediately come to mind. And when it comes to nutritional yeast which is often called for in vegan cooking, while a tablespoon does have a decent amount of B12, it's worth considering that most recipes rarely call for more than a couple of tablespoons for the whole recipe.

Animal Sources of Vitamin B12:

  1. Cooked Beef (100g) - Approximately 3.5 mcg of B12

  2. Cooked Lamb (100g) - Approximately 3.5 mcg of B12

  3. Salmon (100g) - Approximately 2 to 6 mcg of B12

  4. Trout (100g) - Approximately 2 to 6 mcg of B12

  5. Sardines (100g) - Approximately 2 to 6 mcg of B12

  6. Eggs (1 large) - Approximately 0.6 mcg of B12

  7. Milk (1 cup) - Approximately 0.4 to 0.9 mcg of B12

  8. Yogurt (1 cup) - Approximately 0.4 to 0.9 mcg of B12

  9. Cooked Chicken (100g) - Approximately 0.3 to 0.5 mcg of B12

  10. Cooked Turkey (100g) - Approximately 0.3 to 0.5 mcg of B12

  11. Cheese (30g) - Approximately 0.2 to 1.5 mcg of B12 (varying based on type)

Vegetarian and Vegan Sources of vitamin B12:

  1. Fortified Breakfast Cereals - Approximately 1 to 6 mcg of B12 per serving

  2. Nutritional Yeast (1 tablespoon) - Approximately 2.4 mcg of B12

  3. Fortified Plant-Based Milk Alternatives (1 cup) - Approximately 0.5 to 3 mcg of B12

Lifestyle Tips to Support B12 Absorption

Stressed and fatigued woman

Managing Stress and Fatigue:

Chronic stress can deplete B12 levels in the body. Engaging in stress-reducing activities like meditation, yoga, and spending time in nature can promote better B12 absorption.

These guides to a body scan meditation and progressive muscle relaxation can help reduce stress and improve grounding. Try meditation with some aromatherapy for additional sensual support. Some people like lavender, and if this is your thing I would suggest High Altitude French lavender, Lavandula angustifolia. I personally like the combination of peppermint and sweet orange as an uplifting and stress relieving scent. Patchouli can also help support endurance during long stressful times.

Gut Health and B12 Absorption:

Gut health plays a crucial role in the absorption of Vitamin B12. Conditions affecting gut health, such as gastrointestinal disorders or surgeries that impact the stomach or small intestine, may compromise B12 absorption, leading to B12 deficiency. Maintaining gut health through a balanced diet, regular probiotic consumption, and addressing any digestive issues are essential for optimizing B12 absorption and overall well-being. Read this article “Good Mood Food: Fermented Foods and Happiness” for ideas on how probiotics from fermented foods can support gut health.

If I Am Deficient in B12, How Should I Supplement?

There was an interesting study done in 2002 (1), which showed that high dose oral vitamin B12 was just as good as B12 injections in patients who were anemic due to a B12 deficiency. The conclusion from the study stated “Daily oral cyanocobalamin at doses of 1000-2000 microg can be used for treatment in most cobalamin-deficient patients who can tolerate oral supplementation.” The paper made no claims on supplementation for people who have neurological manifestations of B12 deficiency. My experience in practice is in the neurological setting and I have found (anecdotally) that oral supplementation is very effective. Blood levels of B12 rapidly normalize with consistent oral supplementation and I have almost never needed to resort to vitamin B12 injections. Oral vitamin B12 is more convenient and less expensive than vitamin B12 injections so this is what I would typically suggest unless there is a specific reason that would sway my decision. It is worth doing some repeat labs after supplementing for a few months.

A handful of supplements

Combining Vitamin B12 with Other Nutrients:

Combining Vitamin B12 with other nutrients can enhance its overall effectiveness and provide comprehensive support for various bodily functions. One essential nutrient to pair with B12 is folic acid (Vitamin B9). B12 and folic acid work synergistically in the synthesis of DNA and red blood cells. Adequate levels of both nutrients are crucial for preventing certain types of anemia and supporting overall cellular health. Additionally, B12 can be combined with other B-complex vitamins, such as B6 and B5, to create a balanced and comprehensive B-vitamin supplement. B-complex vitamins work together to support energy metabolism, nerve function, and healthy skin, hair, and nails. Moreover, Vitamin C can aid in B12 absorption, as it helps convert B12 into its active form within the body.


Navigating the world of vitamin B12 testing and supplementation is far from simple. Remember, the optimal approach involves a dual testing strategy—measuring both vitamin B12 and methylmalonic acid levels together. The standard "normal" range might not tell the whole story, as different health aspects have different requirements. To truly thrive, target vitamin B12 levels above 300 pg/mL, coupled with a balanced methylmalonic acid level.

Don't forget that B12-rich options extend beyond meat. Yogurt can surpass chicken in B12 content, while nutritional yeast adds a unique twist to dietary choices. To boost B12 absorption, reduce stress and prioritize gut health. Meditation and probiotics can foster a healthier absorption environment.

When it comes to supplementation, research suggests that high-dose oral B12 can rival injections, often with added convenience and cost-effectiveness. For optimal support, blend B12 with folic acid and other B-complex vitamins, while leveraging the absorption power of Vitamin C.

Remember, it's a symphony of nutrients that create the harmony of a healthier life!

Reference article

And another article for bedtime reading...


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