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Vitamin B12: A Guide to Everything You Need to Know

written by Dr. Bolanle Aina - May 3, 2021
medically reviewed by Dr. Christine Bishara, MD - Jun 9, 2021

What is Vitamin B12?

Vitamin B12 (cobalamin) is a water soluble vitamin that serves as a co-enzyme for various metabolic processes in the body such as break down of carbohydrates and fat, build-up of protein molecules, DNA synthesis during cell replication and production of hemoglobin. Vitamin B12 is also required for synthesis of myelin (nerve protein), which is essential for proper nerve function. Therefore, Vitamin B12 is important for healthy metabolism, healthy blood cells and optimal nerve function. It binds to a protein in the stomach call intrinsic factor which facilitates its absorption further down into the small intestine.

What are the different forms of Vitamin B12?

Vitamin B12 is available as cyanocobalamin, methylcobalamin, hydroxocobalamin, adenosylcobalamin, which are all synthetic forms. Cyanocobalamin is the cheapest to produce and thus the most common form of Vitamin B12 supplements available. In the body system, cyanocobalamin is converted to methylcobalamin, which is the form that is more usable in the body.

What is Vitamin B12 used for?

Vitamin B12 is used in the treatment of Vitamin B-12 deficiency and or anemia due to vitamin B12 deficiency. It can also be used off-label for the treatment of recurrent apthous ulcers or canker sores.

Why do I need to take Vitamin B12 as supplement?

Vitamin B12 is an important vitamin that plays a role in the health of the body’s nerve and blood cells as well as formation of DNA. This is partly why requirements increase in early pregnancy. Vitamin B12 also plays an important role in numerous other cellular functions as well as in heart health, as it has also been shown to help regulate levels of the amino acid homocysteine. High homocysteine levels have been shown to increase risk of coronary artery disease by increasing clot formation in blood vessels. Vitamin B12 deficiency has been shown to increase homocysteine levels. Your doctor may recommend you to start taking vitamin B12 supplements if you exhibit any conditions or risk factors that may increase risk of deficiency.

What are the symptoms of Vitamin B12 deficiency?

Some of the symptoms of vitamin B12 deficiency overlap with other conditions. For example pale looking, fatigue, muscle weakness, numbness and tingling in the hands and feet, rapid heart rate, abnormal gait, nausea, vomiting, loss of appetite, symptoms of anxiety or depression. It is important to discuss with your doctor to rule out other possible causes of these symptoms such as iron-deficiency anaemia in which case iron supplements may be needed.

What are the causes of Vitamin B12 deficiency

The 2 main causes of vitamin B12 deficiency are inadequate consumption in diet and/or inadequate absorption from the gastrointestinal tract. Inadequate consumption is common in people with poor diet or restrictive diet such as a purely vegan diet. In some cases, even if adequate amount of B12 is consumed, there may still be a problem with absorption, if there is a deficiency of intrinsic factor, a protein that is needed for Vitamin B12 to be successfully absorbed from the GI lumen into the blood stream. Other causes of impaired vitamin B12 absorption may include Crohn’s disease, prolonged use of metformin or proton-pump inhibitors, gastric bypass surgery. Furthermore, excessive alcohol intake may reduce vitamin B12 absorption from the gastrointestinal tract.

How long do I need to take Vitamin B12 for?

Recovery from Vitamin B12 deficiency is gradual and may take up to 6 to 12 months. Depending on the cause of your deficiency, you may need to be on Vitamin B12 supplement life-long. Treatment with vitamin B12 reverses anaemia and gastrointestinal symptoms and halts the progression of nerve damage. But some neurological damages cannot be completely reversed.

Can I buy Vitamin B12 over-the-counter?

Vitamin B12 requires a prescription in the US therefore it is important to visit your doctor to obtain a prescription for Vitamin B12.

Vitamin B12 dosage forms

Vitamin B12 is available as oral tablets, sublingual tablets, and injectable form for injection into the muscle. Canadian Pharmacy Online has only the generic Vitamin B12 injection manufactured by Sandoz or Sterimax from Canada, or another generic brand called Dodex by Deva Pharma from Turkey. The injection form is valuable in people who have problems in absorption of the drug when taken orally. Also the injection is taken less frequently such as weekly, bi-weekly, or monthly. The injection may be administered by a health care professional or the patient may be trained to self administer.

Vitamin B12 tablets are available from different Canadian manufacturers such as Jamieson, Webber or Swish Herbal. In choosing between oral or sublingual form, it’s all a matter of choice. Although the sublingual form is supposed to afford greater absorption, clinical studies have shown that sublingual route of administration is equally as effective as oral route in treating vitamin B12 deficiency in a group of patients.

What is the difference between Vitamin B12 and Vitamin B complex?

Vitamin B complex differs from Vitamin B12 in that it contains a variety of B-vitamins formulated together in the same pill. So Vitamin B complex contains vitamin B12 in addition to other B-vitamins such as Vitamin B1 (thiamine), B2 (riboflavin), B3 (niacin), B5 (pantothenic acid), B6 (pyridoxine), B7 (biotin), and B9 (folic acid).

Can I give my pets Vitamin B12?

Yes! Your veterinarian may prescribe vitamin B12 for your pet if they exhibit any of the symptoms of vitamin B12 deficiency and if blood test confirms that they have a deficiency. Click here for more information on Vitamin B12 use in pets (cats and dogs)

Can I overdose with Vitamin B12?

It is recommended to follow the labelled directions for use and not take more than necessary. However, Vitamin B12 is water soluble and so if you were to take more than needed, the excess will be eliminated from your body via the urine.

Is Vitamin B12 safe during pregnancy and lactation?

Vitamin B12 is safe and compatible with pregnancy and breastfeeding. In fact low vitamin B12 levels may have undesirable outcomes in pregnancy and in breastfed infants. Therefore pregnant and breast feeding women should be treated if required.

Vitamin B12 containing foods

Natural animal sources of vitamin B12 include the following: organ meats, beef, pork, poultry, fish (haddock, salmon, tuna), shell fish, dairy products (milk, cheese, yoghurt), fortified cereals, eggs. Most common sources of vitamin B12 are animal products, thus it may be more challenging for people on vegetarian or vegan diet to get adequate vitamin B12 from their diet alone. Some vegetarian or vegan diet sources of Vitamin B12 include fortified plant based beverages (soy or almond beverage), soy burgers and nutritional yeast.


Bio: Dr. Bolanle Aina is a licensed pharmacist currently practicing in the community/retail sector. She also holds a Master of Science degree and Doctor of philosophy degree in Pharmacy from the University of Manitoba. She is passionate about health information and medical communication to promote healthy living and optimal drug therapy.


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