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Vitamin B12 - Uses and FAQs

Since I've passed a recent exam, I've gained a few new prescribing rights, including ability to administer intramuscular cobalamin injections...a.k.a Vitamin B12 shots!

Here's what you need to know about Vitamin B12 in general:

It's required for:

-nerve function: to prevent and treat peripheral neuropathies

-brain health: memory, mood, and function

-carbohydrate and protein metabolism

-red blood cell production a.k.a oxygen delivery to tissues

-cardiovascular health

-DNA repair and synthesis

Signs & symptoms of deficiency or sub-optimal levels:

-fatigue, weakness, or vague "unwell" feeling

-depression or anxiety

-neuralgias/neuropathies - tingling and numbness in hands and feet

-conditions like ADHD, Alzheimer’s disease, MS, etc.

-high blood pressure and cardiovascular disease


-issues with balance and walking

Reasons for deficient/sub-optimal Vitamin B12 levels:

1. Food intake is inadequate - the primary food sources are meat and eggs. Vegans and vegetarians may require supplementation.

2. You have deficient stomach acid production- Stomach acid is required to release Vitamin B12 from proteins bound in food. Seniors are at greater risk of deficiency because stomach acid levels decrease with age, and they don't chew their food as well - both of which are required for proper digestion and release of B12. Chronic stress can result in lower levels of stomach acid because of you need parasympathetic nervous system activity ("rest and digest") to activate the vagus nerve and release of stomach acid while eating. Lastly, certain medications have been implicated in Vitamin B12 deficiency, especially in older patients, like long-term use of PPIs, Metformin, and NSAIDs.

3. Absorption in small intestine is compromised -Food intolerances, IBD, Celiac Disease, infection, dysbiosis etc.

4. You have an undiagnosed autoimmune condition, pernicious anemia - where the immune system attacks the cells in the stomach that release intrinsic factor (IF.) IF is bound to Vitamin B12 once it's released from food, allowing it to be absorbed by the small intestine.


1. Vitamin B12 injection vs. oral supplementation?

-Injection by-passes GI absorption, so eliminates the need for stomach acid and healthy GI mucosa for absorption.

-It's been estimated that 1-4% of 1000mcg oral doses get absorbed, compared to 10% of 1000mcg/mL intramuscular injection.

-Some studies show that injections replete stores faster than oral supplementation

-Oral supplementation is still an effective option and has shown to replete deficiencies (likely due to patients studied with adequate stomach acid and GI integrity) and can be used for maintenance once a deficiency has been corrected.

2. Is Vitamin B12 safe?

-It is a water-soluble vitamin, so excess will not be harmful. An acne-like rash has been reported in some individuals, but this is uncommon.

3. What’s the difference between your Vitamin B12 injection and what I get from my doctor?

-I use methylated cobalamin (Vitamin B12). Our body uses methyl groups to detoxify and remove: waste products, neurotransmitters, medications, and hormones from the body. The methyl group is therapeutic in itself! Medical doctors use a synthetic Vitamin B12, cyanocobalamin, which will increase Vitamin B12 stores, but you don’t get the perks of the methyl group. If you’ve done genetic testing and have MTHFR mutations, methylation is especially important.

4. Will I get an energy boost after a B12 injection?

-Some people do. This tends to be more common for those with deficient or sub-optimal stores.

5. How do I know my Vitamin B12 status?

-Blood work. This test is usually included in routine blood work, especially when presenting with symptoms like fatigue or poor memory. You can have it run by your doctor, or I run it for patients for $22.50 (since I'm not covered by OHIP.)

6. Is the blood test accurate?

-There’s quite a bit of controversy here. Here’s why:

-The reference range used by North American labs is much lower than some countries, like Japan. In North America, you’re considered deficient if your levels are <220pmol/L, whereas in Japan, deficiency is <500pmol/L. That's quite a difference.

-It's also considered a low sensitivity test. If you want to read more on this topic, see my second resource below (written by a Hematologist.)

-There are also studies that have found adequate levels of Vitamin B12 in patient’s blood, but levels in the brain (measured from cerebral spinal fluid samples) are low. Treatment with Vitamin B12 injections then resulted in symptomatic improvement, suggesting serum levels may not be the best reflection of total stores.

-Further urinary testing of B12 metabolites may be warranted if autoimmune- mediated Vitamin B12 deficiency is suspected.

7. Does anything mask Vitamin B12 blood levels?

-Folate or folic acid. Folate or folic acid will improve Vitamin B12-associated anemia (if only a CBC has been run) but neurological consequences can then proceed unnoticed. This has been questioned recently since so much of our food is fortified with folic acid.

8. Where do you receive the injection?

-The most common location is the deltoid muscle in the arm.

-For those with lower muscle tone, the gluteus mm. is another option

-Interestingly – some clinicians are choosing injection site based on additional local benefit of pain relief. For example, injections in the gluteus mm. for piriformis syndrome and injection in the back (erector spinae mm.) for low back pain.

Note -Vitamin B12 is a not a "cure all." There are generally multiple reasons why someone may have a particular symptom (like fatigue) and Vitamin B12 may be part of the reason, but not necessarily the only factor involved.

Still have unanswered questions? Book a free, 15min consult to discuss further or email me at


1. Mohn ES, Kern HJ, Saltzman E, Mitmesser SH, McKay DL. Evidence of Drug–Nutrient Interactions with Chronic Use of Commonly Prescribed Medications: An Update. Pharmaceutics. 2018 Mar 20;10(1):36.

2. Green R. Vitamin B12 deficiency from the perspective of a practicing hematologist. Blood. 2017 Jan 1:blood-2016.

3. Prousky JE. Understanding the serum vitamin level and its implications for treating neuropsychiatrie conditions: an orthomolecular perspective. J Orthomolecular Med. 2010;25.

4. Skerrett PJ. Vitamin B12 deficiency can be sneaky, harmful. Harvard Health Blog. 2013.

5. Issac TG, Soundararajan Soundarya RC, Chandra SR. Vitamin B12 deficiency: an important reversible co-morbidity in neuropsychiatric manifestations. Indian journal of psychological medicine. 2015 Jan;37(1):26.

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