Cyanocobalamin vs. Methylcobalamin: Which Version is Best for Thyroid Health?

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The human body relies on a wide spectrum of vitamins and minerals for good health and wellbeing. We need specific amounts of each micronutrient on a daily basis.

Cobalamin, also known as vitamin B12, is among the most significant micronutrients as we need it for the development, myelination, and function of the central nervous system (CNS).

We also need vitamin B12 for the production of red blood cells, the synthesis of DNA, and other functions. Deficiency in vitamin B12 is possible, especially in persons with thyroid problems. In this post, we discuss Cyanocobalamin and Methylcobalamin or which version could be better for the thyroid.

How common is vitamin B12 deficiency?

According to the National Institutes of Health, most people in the U.S. eat enough vitamin B12. In the United States and the United Kingdom, about 6% of adults younger than 60 are deficient in vitamin B12. Additionally, 20% of people older than 60 have vitamin B12 deficiency.

The same report revealed the risk of vitamin B12 deficiency is higher among persons of low socioeconomic status, women, and non-Hispanic Blacks. Levels of this vitamin in the body may also drop during pregnancy but return to normal after delivery.

It is also useful to mention 24% of men and 29% of women report they use vitamin B12 dietary supplements.

Symptoms of vitamin B12 deficiency

Mild vitamin B12 deficiency may be asymptomatic, i.e., a person doesn’t experience symptoms at all. If left unmanaged and untreated properly, deficiency may aggravate and manifest itself through symptoms such as:

  • Pale skin

  • Tiredness, weakness, and/or lightheadedness

  • Smooth tongue

  • Shortness of breath and heart palpitations

  • Vision loss

  • Nerve problems such as muscle weakness, tingling, and problems with walking

  • Diarrhea or constipation

  • Gas

  • Loss of appetite

  • Memory loss, depression, and other behavioral or mental changes/problems

Vitamin B12 deficiency and hypothyroidism

Hypothyroidism (underactive thyroid gland) is a condition wherein the thyroid doesn’t create and release sufficient amounts of thyroid hormone into the bloodstream. In turn, metabolism slows down, and other symptoms occur. Hypothyroidism is a complex medical problem because it affects or is connected to different aspects of our health. Evidence shows hypothyroidism is linked to vitamin B12 deficiency, too.

One study found 40% of hypothyroid patients also had vitamin B12 deficiency. Interestingly, traditional symptoms of this deficiency arent a good clue to determine the presence of this nutrient deficiency. Scientists explain doctors should screen their patients for vitamin B12 deficiency regardless of their thyroid antibody status. Symptoms improved with the replacement of vitamin B12.

A different piece of evidence, published in the Medical Principles and Practice, found deficiencies in vitamin B12 and D are linked to autoimmune hypothyroidism. There was also a negative link between levels of these vitamins and anti-TPO antibodies.

While more research is necessary on this subject, vitamin B12 deficiency in hypothyroid persons could be due to anemia. Hypothyroidism is strongly associated with anemia, a condition where the body doesn’t have enough healthy red blood cells that would carry oxygen to the tissues. There are different types of anemia, including pernicious anemia, which affects the absorption of vitamin B12 and thereby contributes to deficiency.

How is vitamin B12 deficiency treated?

When left unmanaged properly, vitamin B12 deficiency can be sneaky and harmful. The treatment of this condition depends on its severity. For the mildest forms, simple diet adjustments are enough. Moderate deficiency requires the intake of standard multivitamins to bring vitamin B12 levels to be normal.

A serious deficiency in vitamin B12 is managed through high-dose B12 pills or weekly shots of vitamin B12. In many cases, vitamin B12 deficiency is a preventable issue that you can avoid with a healthy and well-balanced diet.

What are Cyanocobalamin and Methylcobalamin?

In some cases, deficiency in vitamin B12 requires dietary adjustments. Some people may need to take medications such as Cyanocobalamin and Methylcobalamin. Lets introduce these drugs first.

Cyanocobalamin is a synthetic form of vitamin B12 available in prescription or over-the-counter (OTC) form to prevent or treat low vitamin B12 levels. It also prevents or aids the management of anemia caused by vitamin B12. Cyanocobalamin was first manufactured in the 1940s, and it is used as a nasal spray, by mouth, and by injection.

On the other hand, Methylcobalamin is a naturally occurring form of vitamin B12 that you can obtain through diet, supplements, and medications. When it comes to medications, Methylcobalamin is available in the form of pills, injections, nasal sprays. Methylcobalamin is used to address vitamin B12 deficiency, pernicious anemia, and other health problems, including diabetes.

The main difference between Cyanocobalamin and Methylcobalamin

At first glance, Cyanocobalamin and Methylcobalamin seem like they are the same thing going under two different names. Not exactly correct. While both Cyanocobalamin and Methylcobalamin are vitamin B12, they are two different versions of this micronutrient.

The main difference between the two is in what is attached to them. As you can already conclude, in Cyanocobalamin, vitamin B12 is attached to cyanide. In the case of Methylcobalamin, vitamin B12 is attached to a methyl group.

Now you’re probably worried about cyanide since it is fatal to humans. But keep in mind the amount of cyanide, in this case, is too low to cause harm.

Both attachments, cyanide and methyl group, are variations of atoms of carbon and hydrogen. You can easily consider cyanide and methyl groups as carriers that hold onto vitamin B12. These carriers have important roles, though. For example, they stabilize vitamin B12 and potentially modify it when its absorbed. The carriers also influence how tricky it is for the body to assimilate or use the active compound, in this case, vitamin B12. Additionally, the carriers provide us with necessary (or unnecessary even) substrate when the body clears the carrier from vitamin B12.

A vast majority of vitamin B12 formulations are cyanocobalamin type. Why? Cyanocobalamin is cheaper to manufacture and produce.

The body absorbs Cyanocobalamin and Methylcobalamin differently

Since vitamin B12 is attached to different carriersin Cyanocobalamin and Methylcobalamin, the body handles them differently. In other words, your body may not absorb and retain these two versions of vitamin B12 the same way.

In fact, the absorption of Cyanocobalamin could be slightly better than that of Methylcobalamin. A study from the Scandinavian Journal of Gastroenterology found subjects’ bodies absorbed 49% of 1µg (mcg = microgram) dose of Cyanocobalamin, whereas absorption of Methylcobalamin was slightly lower at 44%.

While the body absorbs more from Cyanocobalamin, it doesn’t mean retention is also better. What’s more, evidence confirms Methylcobalamin has a higher retention rate. One study compared the retention of both versions of vitamin B12 and revealed about three times as much Cyanocobalamin was excreted from the body through urine. This means the retention of Methylcobalamin was higher, i.e., it remained in the body for longer.

When we are discussing how the body handles the two versions of vitamin B12, it’s important to mention what happens upon ingestion. As previously stated, Methylcobalamin is a naturally occurring vitamin B12, while Cyanocobalamin is a synthetic type. When you ingest the latter, the body converts it to both active forms of vitamin B12: adenosylcobalamin and Methylcobalamin. Both methyl- and Cyanocobalamin are brought down to a cobalamin molecule that converts to the active forms of this micronutrient in the cells of your body.

Is Methylcobalamin superior to Cyanocobalamin?

Even though both forms of vitamin B12 are used for the treatment of deficiency in this vitamin or management and prevention of anemia, Methylcobalamin could be considered more superior in some aspects. First of all, Methylcobalamin is a naturally occurring form of vitamin B12. For that reason, it is the most bioavailable form of this vitamin. The body can use it upon ingestion, whereas Cyanocobalamin has to be converted to Methylcobalamin first.

Longer retention is yet another reason Methylcobalamin could be considered superior. Basically, longer retention means the body is supplied with this vitamin for longer. Also, this version of vitamin B12 is primarily used in the brain and nervous system, and liver. Whats more, proper function and health of the nervous system require this specific form of vitamin B12.

Methylcobalamin has numerous functions in the body, including converting homocysteine to methionine. Homocysteine is a common amino acid in the blood, but when its levels are high, it could damage arteries and put you at a higher risk of heart disease and stroke. This amino acid induces sclerosis of arteries, thereby forming a strain on the heart and vascular system.

By converting homocysteine to methionine, this version of vitamin B12 can decrease the risks mentioned above. This is particularly important if we bear in mind high homocysteine levels are present in some cases of hypothyroidism.

While the body retains Methylcobalamin longer and can lower homocysteine levels, the best results occur when it’s combined with adenosylcobalamin. On the other hand, to get the most from Cyanocobalamin, you don’t have to combine it with anything else.

Even though as a natural form of vitamin B12 Methylcobalamin is considered superior, in some aspects, Cyanocobalamin may perform better. In other words, both versions have their strengths and weaknesses.

Do Cyanocobalamin and Methylcobalamin interact with thyroid medications?

If youre taking thyroid medications such as levothyroxine and you are also deficient in vitamin B12, its natural to wonder whether these versions of B12 would interact with your therapy. Neither of the two types of vitamin B12 interacts with levothyroxine. That said, you should still consult your doctor before you decide to use over-the-counter forms of this micronutrient. Your doctor will inform you whether its safe to use them. Additionally, when taking Cyanocobalamin and Methylcobalamin, it’s crucial to stick to dosage instructions and avoid altering or increasing the dose on your own.

Are there any side effects?

While generally safe, Cyanocobalamin may induce side effects such as injection site reactions, nausea, upset stomach and diarrhea, rash and itching, dizziness and weakness, headache, tingling or numbness, fever, joint pain, and swelling throughout the body.

Adverse reactions of Methylcobalamin may include nausea and vomiting, diarrhea, headache, and loss of appetite.

The risk of side effects is low when recommended doses are taken.

What are the dosages of both versions?

Generally speaking, for treatment of pernicious anemia, a doctor may recommend an injection of 100mcg of Cyanocobalamin daily for six to seven days. Oral Cyanocobalamin should be taken according to instructions on the packaging.

Also, oral Methylcobalamin should be taken according to instructions. In cases when the injection is necessary, you may need to receive it once to three times a week.

Healthcare professionals will teach you how to administer the medication yourself.

Are these versions of vitamin B12 vegan?

The best sources of vitamin B12 in diet are animal-based foods such as meat, fish, milk, eggs, cheese. Since vegans do not consume animal-based products, they are at a higher risk of vitamin B12 deficiency. The problem becomes even worse if you have thyroid problems and also happen to be a vegan. Correcting vitamin B12 levels through diet can be tricky this way. Supplementation is the answer, but not all products are vegan-friendly.

As a manmade form of vitamin B12 Cyanocobalamin is considered suitable for vegans too. In supplements, Methylcobalamin is also vegan-friendly since it is made by chemically modifying the Cyanocobalamin produced by bacteria that are grown in vats.

But, just to be on the safe side, you may want to read the label and see whether a product is vegan-friendly before you buy. Also, you should buy your vitamin B12 from vegan-friendly brands.


Vitamin B12 is not uncommon, especially in people with thyroid problems such as hypothyroidism. Supplementation is often a practical solution, but some people may need injections. Both Cyanocobalamin and Methylcobalamin are used to treat vitamin B12 deficiency and pernicious anemia. Methylcobalamin is a naturally occurring version of vitamin B12, and the body uses it immediately while retaining it longer.

Cyanocobalamin is a synthetic version of vitamin B12 that is quickly absorbed but excreted faster, and the body needs to convert it to Methylcobalamin before it gets to use it. While both versions have strengths and weaknesses, Methylcobalamin could be more suitable for persons with thyroid problems.


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